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The depth of convective clouds affects vertical transport of atmospheric constituents, influencing downstream weather and climate. Atmospheric controls on the maximum depth reached by moist convection are investigated with radar‐tracked convective cells tagged with sounding‐derived atmospheric parameters from a field campaign in central Argentina. Regression analyses show that narrow (<12‐km diameter) and wide (>16‐km diameter) cell depths respond to disparate factors, where cell areas are defined using composite reflectivity signatures. Undiluted lifted parcel indices including convective available potential energy (CAPE) and level of neutral buoyancy (LNB) are top predictors of wide cell maximum depth while mid‐tropospheric relative humidity is the top predictor of narrow cell maximum depth. Because narrow cells are more numerous than wide cells, the overall outcome of the full cell population does not strongly correlate with CAPE and LNB conditions. Tracked cells and atmospheric conditions in a simulation with 3‐km grid spacing covering the field campaign produce similar results to those observed. Narrow cells that are relatively deep have a cooler and moister mid‐troposphere with weaker free tropospheric subsidence, while relatively deep wide cells have much warmer and moister lower tropospheric conditions. These atmospheric differences are present 1 hr before cell initiation at both a fixed observing site and variable cell initiation locations. Simulated narrow cell maximum equivalent potential temperature decreases with height at a rate similar to the ambient vertical gradient, causing these cells to fall short of their LNB and supporting the view that entrainment‐driven dilution is a dominant control on their depth. Plain Language Summary: The depth that storms reach impacts where the heat, moisture, momentum, aerosols, and trace gases that they are transporting are deposited, but this depth is difficult to predict because most storms fall short of their theoretically maximum possible depth. The reason for this shortfall is that most storms are narrow, such that they are effectively diminished by mixing with surrounding drier air as the storm deepens. Thus, a dominant control on the depth of these clouds is the humidity of this surrounding air. However, wide storms are less vulnerable to destructive mixing with dry air. As a result, they more consistently reach depths that are well predicted by theory. These conclusions were reached via analysis of over a thousand storms over several months using field experiment measurements and a computer simulation. Key Points: Wide convective cell depth responds most to available instability, while narrow cell depth responds most to midlevel relative humidityEntrainment‐driven reduction of buoyancy decreases as cell width increases, causing disparate narrow and wide cell depth responsesA convection‐permitting simulation with 3‐km horizontal grid spacing generally reproduces observed relationships [ABSTRACT FROM AUTHOR]

Implicit time‐stepping for advection is applied locally in space and time where Courant numbers are large, but standard explicit time‐stepping is used for the remaining solution which is typically the majority. This adaptively implicit advection scheme facilitates efficient and robust integrations with long time‐steps while having negligible impact on the overall accuracy, and achieving monotonicity and local conservation on general meshes. A novel and important aspect for the efficiency of the approach is that only one iteration is needed each time the linear equation solver is called for solving the advection equation. The demonstration in this paper uses the second‐order Runge‐Kutta implicit/explicit time integration in combination with a second/third‐order finite‐volume spatial discretization and is tested using deformation flow tracer advection on the sphere and a fully compressible model for atmospheric flows. Tracers are advected over the poles of highly anisotropic latitude‐longitude grids with very large Courant numbers and on quasi‐uniform hexagonal and cubed‐sphere meshes with the same algorithm. Buoyant flow simulations with strong local updrafts also benefit from adaptively implicit advection. Stably stratified compressible flow simulations require a stable combination of implicit treatment of gravity and acoustic waves as well as advection in order to achieve long time‐steps. Plain Language Summary: Weather and climate prediction models take small time‐steps in order to make predictions about the future, starting from estimates of current conditions. The smaller the time‐steps are, the more of them have to be taken to make a prediction for a given time in the future. The more time‐steps that have to be taken, the more expensive the prediction is. If the time‐steps are too big, models can not only lose accuracy, they can become unstable—inaccuracies can become so large that wild oscillations are generated and the model crashes. These instabilities are often caused by the advective transport of constituents of the atmosphere by the wind. This paper describes a method—adaptive implicit advection—for calculating atmospheric transport using longer time‐steps while maintaining stability. We show that this can be achieved with minimal additional cost, and accuracy is only lost locally, where the time‐step is large relative to the flow speed and model grid size. Key Points: Implicit time‐stepping for advection enables large Courant numbersImplicit time‐stepping for advection is cheap as it combines an explicit correction with a simple first‐order accurate implicit estimateImplicit time‐stepping enables monotonicity, conservation and unconditional stability [ABSTRACT FROM AUTHOR]

Global warming has changed both the amount of global precipitation and the atmospheric capacity to retain water. In this paper, a novel definition of the long‐term Capturability of Atmospheric Water (CAW) based on horizontal atmospheric water transport is proposed, describing the ability of a certain area to intercept and convert the atmospheric water transported by horizontal moisture flux into local precipitation. The significant decrease of the CAW in Amazon and Congo rainforests and Inside Greenland indicates that these areas were having less precipitation with the same water vapor in the past 42 years, while in Asia (especially China), CAW is showing a large‐scale increasing trend, verifying the regional humidifying. Considering the change of both the CAW and the background atmospheric water simultaneously, their mismatch degree is also investigated. The positive mismatch in Qinghai Tibet Plateau, Greenland, and the Andes, suggests higher susceptibility to climate change, and in the areas of negative mismatch (Amazon, Maritime Continent, southeastern China, the Eastern United States, India, and Japan), a more stable precipitation response to climate change is expected. The proposed concept of CAW provides a novel perspective to analyze the precipitation response to climate change on a global scale. Key Points: A novel definition of long‐term Capturability of Atmospheric Water (CAW) based on horizontal transport is proposedIn the past 42 years, the CAW in the Amazon and Congo rainforests and the Greenland ice sheet has degraded significantlyThe findings provide a perspective to analyze the precipitation response to global climate change [ABSTRACT FROM AUTHOR]

Air‐sea heat and moisture fluxes modulate the surface energy balance and oceanic and atmospheric heat transport across all timescales. Spatial gradients of these fluxes, on a multitude of spatial scales, also have significant impacts on the ocean and atmosphere. Nevertheless, analysis of these gradients, and discussion regarding our ability to represent them, is relatively absent within the community. This letter discusses their importance and presents a wintertime climatology. Their sensitivity to spatiotemporal scale and choice of data set is also examined in the mid‐latitudes. A lead‐lag analysis illustrates that wintertime air‐sea heat flux gradients in the Gulf Stream can precede the North Atlantic Oscillation by ∼1 month. A lack of observations and thus validation of air‐sea heat flux gradients represents a significant gap in our understanding of how air‐sea processes affect weather and climate, and warrants increased attention from the observational and modeling communities. Plain Language Summary: The oceans impact both weather and climate by heating and cooling the lower atmosphere. Surface latent (sensible) heat flux is a quantity that measures the exchange of heat associated with evaporation of seawater (an air‐sea temperature difference). In addition to the absolute exchange, the manner in which the exchange varies spatially (the heat flux gradients) is also known to be important for the development of weather systems and longer‐term climate. Despite this, relatively little attention is paid in the literature to variability in these gradients. This study provides a brief overview of their importance and provides a wintertime climatology in these gradients. It is also illustrated that when considering gradients, the importance of specifying the spatial scale over which the gradient is calculated is critical. Although many differences exist between air‐sea heat flux data products in these gradients, there are currently almost no observations to validate them in key areas of interest, which represents a significant deficiency in our understanding of ocean‐atmosphere interactions. This is emphasized by demonstrating that these gradients in the mid‐latitudes can statistically precede variability in the North Atlantic Oscillation, the most important mode of monthly atmospheric variability in the North Atlantic. Key Points: Air‐sea heat and moisture flux gradients modulate important oceanic and atmospheric processes across a multitude of spatiotemporal scalesAir‐sea heat flux gradient variability can statistically precede mid‐latitude atmospheric variabilityNotable air‐sea heat and moisture flux gradient inconsistencies exist in data products, yet the ability to validate them remains elusive [ABSTRACT FROM AUTHOR]

Extreme integrated vapor transport (IVT) is a crucial driving factor of extreme precipitation events (EPEs). This paper presents a complex network‐based characterization of propagations from extreme IVT to EPEs. Specifically, the propagations are tracked from extreme IVT to EPEs by event synchronization; and then the source zones of extreme IVT contributing to EPEs are identified by two‐layer complex network. A case study is devised for North America based on the daily NCEP/NCAR Reanalysis 1 from 1948 to 2021. Overall, eight communities of EPEs are identified: the west coast of United States (US) tend to receive substantial EPEs from the Pacific Ocean; the Gulf of Alaska tends to receive oceanic EPEs propagating inland; western Canada typically experiences large amount of out tendencies and the EPEs tend to accumulate in the Baffin Island and Labrador Peninsula; the southeastern US and the northern Great Plains tend to experience northward propagations from Mexico. Along the west coast of North America, the propagations from extreme IVT to EPEs typically originate from the eastern North Pacific between 160°W and 110°W, and make landfalls in 4 days. These propagations are influenced by anomalous cyclonic circulations developing over the Gulf of Alaska forced by eastward Rossby waves. The coincidence rate of these propagations with atmospheric rivers is, respectively, 85.31% in autumn, 91.35% in winter, 73.94% in spring, and 64.52% in summer. Overall, the observed propagations from extreme IVT to EPEs yield insights into the mechanism of atmospheric moisture transport and the predictability of precipitation. Plain Language Summary: Owing to different synoptic systems such as atmospheric rivers, low‐level jets, and tropical cyclones, there exist profound propagations from extreme integrated vapor transport to extreme precipitation. Focusing on North America, this paper is concentrated on the complex network underlying extreme integrated vapor transport and extreme precipitation events. It is found that the Rocky Mountains play an important part in shaping the propagations from extreme integrated vapor transport to extreme precipitation events. In particular, along the west coast of North America, extreme integrated vapor transport originating from the eastern North Pacific tends to be blocked by the Rocky Mountains, causing rising/cooling and leading to extreme precipitation. Overall, along the Rocky Mountains, there exist eight communities of extreme precipitation. Key Points: There exists a complex network on propagations from extreme integrated vapor transport to extreme precipitation events in North AmericaIn the west coast of North America, the propagations typically originate from eastern North Pacific and make landfalls in 4 daysThe coincidence rate of propagations with atmospheric rivers is, respectively, above 90% and 60% in boreal winter and summer [ABSTRACT FROM AUTHOR]

Major explosive volcanic eruptions were important triggers of abrupt climate changes during the Holocene and crucial sources of Hg to the atmosphere, yet there remains limited understanding regarding the long‐range transportation of this volcanic Hg and its imprint in natural archives. Here, we present a reconstruction of Holocene global volcanism based on the anomalies in Hg concentrations, accumulation fluxes, and Hg/C ratios in three high‐resolution peat profiles spanning Eurasia. Our reconstruction reveals that the two Tibetan peat profiles recorded 33 major explosive volcanic eruptions (with 11 eruptions being synchronously detected), which correspond with a French Pyrenees peat record and sulfate anomalies in polar ice cores. Additionally, the major explosive volcanic eruptions recorded in the TP peat profiles coincided with abrupt decreases in solar irradiance during the Holocene, suggesting these eruptions might have had a greater global climate impact. Our results suggest the atmospheric transport of volcanic Hg within the Northern Hemisphere and underscore the significant role played by major explosive volcanic eruptions in precipitating abrupt global climate and environmental changes during the Holocene. This study has implications for deciphering the configuration of volcanic eruption seasons, locations, and magnitudes during the Holocene and aligning the chronology of peat deposits with ice cores. Plain Language Summary: Major explosive volcanic eruptions, one of the principal geogenic sources of Hg to the atmosphere, are widely acknowledged as significant drivers of abrupt global environmental and climate changes during the Holocene. While the magnitudes and timing of these eruptions have been well documented in ice core records, the long‐range transportation of the volcanic materials (such as Hg and SO2) and their terrestrial dispersion remain largely unknown. In this study, we present a reconstruction of Holocene global volcanism based on the anomalies in Hg concentrations, accumulation fluxes, and Hg/C ratios in three high‐resolution peat profiles, with two collected from the Tibetan Plateau and one from the French Pyrenees. Our reconstruction reveals that the Tibetan peat profiles recorded 33 major volcanic eruptions, which correspond with a French peat record and the sulfate anomalies in polar ice cores. Additionally, we demonstrate that certain major explosive volcanic eruptions likely triggered several abrupt decreases in solar irradiance during the Holocene. Our findings suggest the convective atmospheric transport of volcanic Hg within the Northern Hemisphere extratropical region and underscore the significant role played by major explosive volcanic eruptions in precipitating abrupt global climate and environmental changes during the Holocene. Key Points: Eleven major explosive volcanic eruptions during the Holocene were synchronously recorded in two peat profiles in the Tibetan PlateauThe recorded major explosive volcanic eruptions coincide with nine abrupt decreases in solar irradiance during the HoloceneThe Hg anomalies in peat profiles have the potential to be chronology markers that were linked with volcanic eruptions [ABSTRACT FROM AUTHOR]

The North Pacific is known with iron limitation for phytoplankton growth in the subarctic region and nitrogen limitation in the subtropical gyre. Although the growth rate of phytoplankton is determined by the concentration of limiting nutrient, the supply ratio of iron to nitrogen is suggested to be essential to this biogeographic pattern. However, the underlying dynamics determining the ratio remain largely unknown. We investigated mechanisms of dissolved iron (dFe) and nitrate (NO3−) transport to the euphotic zone of the North Pacific using an eddy‐resolvable biogeochemical model. We show that lateral advection and atmospheric deposition are dominant drivers for dFe transport, resulting in high Fe:N supply ratio in both subarctic and subtropical regions. Conversely, significant vertical supplies of NO3− through upwelling and diffusion processes markedly reduce the supply ratio in the subarctic region. These dynamics combined lead to high Fe:N supply ratio in the gyre and low ratio in the subarctic, ultimately driving high nitrogen fixation condition in the gyre and the iron‐limited phytoplankton growth condition in the subarctic region. Plain Language Summary: Iron is a critical trace element for the photosynthesis and nitrogen fixation of phytoplankton in the ocean. In North Pacific Subarctic region, although there is plenty of nitrate, the growth of phytoplankton is limited due to the lack of iron. In the North Pacific Subtropical Gyre (NPSG), nutrient supply to the surface is restricted due to ocean stratification, but diazotrophs can fix nitrogen from the atmosphere. However, their growth is also constrained by iron availability. Understanding how nutrients like iron reach the ocean's surface is vital for predicting the productivity of marine life. Our research employed advanced computer models to explore how dissolved iron is transported in the North Pacific. We discovered that lateral transport by ocean currents, followed by atmospheric deposition, is the primary pathway for iron delivery to the sunlit layer of the NPSG. In the Subarctic Gyre, atmospheric deposition and vertical advection are the major sources of iron. However, we found different transport patterns for nitrate, revealing that physical process‐controlled supply ratio of iron to nitrate may determine where different types of phytoplankton thrive in the surface ocean. This research helps understand the complex processes that supply nutrients to ocean surface. Key Points: Lateral transport and atmospheric deposition dominate supplies of dissolved iron (dFe) to the euphotic zone of the North PacificUpwelling and vertical diffusion control nitrate (NO3−) supply in subarctic regionLateral dFe and vertical NO3− transports determine the stoichiometric supply ratio and shape the biogeographic pattern [ABSTRACT FROM AUTHOR]

Sustained near‐surface ozone pollution despite stringent emission controls in China has drawn wide attention. However, how such rapid regional emission reductions affect global tropospheric ozone remains unexplored. Here, using an ensemble of measurements and global model simulations, we find Chinese emission reductions during 2013–2020 have increased domestic surface ozone; particularly in North China, they have decreased the global tropospheric ozone burden by 2.7 Tg (54% of China's anthropogenic contribution and 7% of global anthropogenic contribution in 2019) and ozone radiative forcing by 8.8 mW m−2 (64% of China's anthropogenic contribution and 9% of global anthropogenic contribution in 2019). Nitrogen oxides (NOx) associated nonlinear chemistry and height‐dependent atmospheric transport patterns primarily cause the contrasting impacts. Future Chinese NOx emission controls would continue to decrease global tropospheric ozone, while regional surface ozone may still increase unless NOx reductions exceed ∼53% of the 2019 level. Our results reveal the substantial benefit of regional emission reductions in China on global tropospheric ozone mitigation. Plain Language Summary: Tropospheric ozone is an important air pollutant and greenhouse gas and mainly produced by atmospheric photochemical reactions. Its levels are largely impacted by anthropogenic emission sources. Over the past decade, anthropogenic emissions in China have greatly declined, which may alter tropospheric ozone on a global scale. Using numerical simulations from a global chemical transport model, we show that emission reductions in China have substantially decreased the global tropospheric ozone burden over 2013–2020. The emission reductions have reduced the global anthropogenic tropospheric ozone radiative forcing and the Chinese contributions by 9% and 64%, respectively, although the emission reductions increased domestic surface ozone over North China. The differences in the nitrogen oxides (NOx) associated ozone formation regimes and atmospheric transport mechanisms over the surface of North China and the free troposphere primarily cause the contrasting impacts. We estimate that further emission reductions of NOx in China would cause nonlinear domestic and global tropospheric ozone changes. Our assessment demonstrates that emission reductions in China help global tropospheric ozone mitigation. Deep emission reductions are needed to further reduce domestic ozone pollution in China. Key Points: Emission reductions in China have substantially decreased the global tropospheric ozone burden and its radiative forcingDifferences in ozone chemistry and atmospheric transport mechanisms cause contrasting domestic and global impactsFuture NOx reductions in China would further mitigate global tropospheric ozone despite short‐term domestic surface ozone increases [ABSTRACT FROM AUTHOR]

Zinc (Zn) exerts a significant influence on the global environment, terrestrial ecosystems, and human health. The application of Zn isotopes (δ66Zn) has been suggested as a potent tool for tracing environmental contamination. However, studies focusing on Zn isotope tracing within the cryosphere areas are notably limited. Here we present the first data set on Zn isotopes in glacial cryoconite, based on observations over a large regional scale in High Asian Mountains (including Tibetan Plateau (TP) and its surroundings of western China). The results showed that glacial cryoconite had a general heavy Zn isotopic signature in various TP locations, with δ66Zn values ranging from −0.22‰ to +0.87‰. Employing the MixSIAR model, the overall Zn contribution source to the cryoconite was mineral dust (36%) > coal burning (33%) > non‐exhaust traffic emissions (22%) > industrial smelting (10%). We ascertained that anthropogenic sources account for the primary contribution (about 60%–73%) of Zn inputs in all glacial locations, with coal burning emerging as the foremost anthropogenic contributor (mean 33%). Anthropogenic Zn in various TP locations was primarily derived from Zn emissions resulting from coal combustion, though it is also predominantly influenced by industrial smelting source in cryoconite of the Tianshan Mountains. Our results aligned with coal combustion data from the energy inventory of western China, suggesting that regional coal burning likely represents the foremost source of atmospheric Zn pollutant emission and deposition in the High Asia mountain glaciers. Plain Language Summary: This is the first to investigate Zn isotope deposition in glacial cryoconite on a large scale in the High Asian Mountains. We find that anthropogenic sources dominate glacial Zn input, contributing approximately 60%–73%, with coal combustion being the most significant anthropogenic source, accounting for a mean of 33%. This study underscores the significant potential of Zn isotopes in cryoconite for tracing atmospheric pollution transport routes and identifying pollutant sources. Key Points: The first study of Zn isotopes as geo‐environmental tracers for Zn sources and pathways in large range glacial environmentAnthropogenic emissions constitute the main source of Zn in all glacial areas, with the largest origins associated with coal burningCoal‐related Zn emissions in western China and surrounding areas (including South Asia and East Asia) influence the Tibetan Plateau environment [ABSTRACT FROM AUTHOR]

The equatorward contraction of tropical precipitation, commonly referred to as the "deep‐tropical contraction", is witnessed in the paleoclimate simulations of the early Eocene. However, the mechanism driving this contraction is still unclear. Based on the energetics framework of the Intertropical Convergence Zone (ITCZ) and the decomposition method of the latent heat flux along with the simulations of a climate system model, CESM1.2, we proposed a novel mechanism responsible for the "deep‐tropical contraction" in the early Eocene. The greenhouse gases‐induced sea surface warming amplifies the sensitivity of evaporation to surface wind speed changes through Clausius‐Clapeyron scaling, leading to an interhemispheric asymmetric enhancement of the latent heat flux. To maintain hemispheric energy balance, the cross‐equatorial atmospheric energy transport must be reduced during the solstice seasons. As a result, the solstitial location of the ITCZ shifts equatorward, causing the "deep‐tropical contraction" in the early Eocene. Plain Language Summary: The early Eocene is the warmest epoch in the last 65 million years, with a global mean temperature 9°C–23°C higher than the preindustrial period. According to state‐of‐the‐art climate models, the tropical rainfall contracted toward the equator during this extremely warm period. However, the physical mechanism causing this phenomenon remains unclear. In this study, we examined the hemispheric energy balance in the early Eocene that causes the equatorward contraction of tropical precipitation. A novel mechanism underlying this phenomenon is revealed. Based on the climate modeling of CESM1.2, we show that the GHG‐induced warmth enhances the sensitivity of evaporation to surface wind speed changes in the early Eocene. Thus, the stronger tropical trade wind in the winter hemisphere will drive out stronger latent heat flux than in the summer hemisphere. This interhemispheric asymmetric response reduces the interhemispheric heating contrast in the solstice seasons. As a result, the ascending motion in the tropical atmosphere migrates toward the equator, finally decreases the width of tropical precipitation in the early Eocene. Key Points: The "deep tropical contraction" in the early Eocene is caused by the equatorward migration of the seasonal ITCZThe equatorward migration of the solstitial ITCZ location in the early Eocene is due to decreased cross‐equatorial energy transportThe enhanced wind‐evaporation effect in the early Eocene reduces the cross‐equatorial atmospheric energy transport in the solstitial seasons [ABSTRACT FROM AUTHOR]

A comprehensive modeling study has been conducted to investigate space weather effects at Mars during the 10 September 2017 solar flare, utilizing an integrated framework that combines the global magnetohydrodynamic (MHD) model and Mars Global Ionosphere‐Thermosphere Model (MGITM). This is the first time the thermosphere‐ionosphere‐magnetosphere system is self‐consistently simulated under realistic, time‐varying conditions. Our simulations align well with observations from the Mars Atmosphere and Volatile EvolutioN (MAVEN). Recognizing that complexities due to highly disturbed upstream conditions and rotating crustal fields obscure solar flare effects in orbit‐to‐orbit comparisons, we perform controlled simulations of nonflare and flare cases and exploit their contrast to quantify spatiotemporal variations in flare impact. Our results highlight pronounced and rapid dayside ionospheric perturbations, contrasting with weaker and delayed nightside responses. Notably, in the topside ionosphere, O2+ ${\mathrm{O}}_{2}^{+}$ and CO2+ ${\mathrm{O}}_{2}^{+}$ densities increase primarily on the dayside below ∼ ${\sim} $300 km altitude, peaking with an increase of 20%–30%. The O+ ${\mathrm{O}}^{+}$ density shows a more significant increase of up to ∼ ${\sim} $50%, extending into the magnetosphere and nightside via plasma transport, increasing its total loss rate by 14%. We observe distinct altitude‐dependent patterns in dayside electron density enhancements in percent, characterized by a weakening with altitude and a rapid decay below ∼ ${\sim} $150 km in line with the flare development, and a gradual intensification between ∼ ${\sim} $150–300 km due to plasma transport and flare‐induced atmospheric upwelling. Earlier Mars Global Surveyor observations were limited to the low‐altitude pattern due to atmospheric expansion and missed the higher altitude variations observed by MAVEN. Plain Language Summary: This study investigates the impact of a powerful X8.2‐class solar flare on 10 September 2017 at Mars. Using an integrated modeling framework that combines two state‐of‐the‐art global models, our simulations provide insights into distinct altitude‐dependent patterns of flare‐induced ionospheric density enhancements, pronounced day‐night asymmetry, and a moderate increase in ion escape. Key findings include rapid variations in ionospheric density enhancements at lower altitudes, with a gradual intensification at higher altitudes due to plasma transport and atmospheric upwelling. These findings contribute to a better understanding of how solar flares impact the space environment of unmagnetized or weakly‐magnetized planets like Mars. Key Points: The solar flare causes pronounced and rapid dayside ionospheric perturbations and weaker and delayed effects on the nightsideO2+ and CO2+ densities increase by 20%–30% above 150 km on the dayside, while O+ increases by up to 50% and over larger spacePercentage increase of dayside e− densities decreases with altitude and decays fast below ∼150 km, and rises and decays slowly above that [ABSTRACT FROM AUTHOR]

Many super‐Earths are on very short orbits around their host star and, therefore, more likely to be tidally locked. Because this locking can lead to a strong contrast between the dayside and nightside surface temperatures, these super‐Earths could exhibit mantle convection patterns and tectonics that could differ significantly from those observed in the present‐day solar system. The presence of an atmosphere, however, would allow transport of heat from the dayside toward the nightside and thereby reduce the surface temperature contrast between the two hemispheres. On rocky planets, atmospheric and geodynamic regimes are closely linked, which directly connects the question of atmospheric thickness to the potential interior dynamics of the planet. Here, we study the interior dynamics of super‐Earth GJ 486b (R=1.34 $R=1.34$R⊕ ${R}_{\oplus }$, M=3.0 $M=3.0$M⊕ ${M}_{\oplus }$, Teq≈700 ${\mathrm{T}}_{\text{eq}}\approx 700$ K), which is one of the most suitable M‐dwarf super‐Earth candidates for retaining an atmosphere produced by degassing from the mantle and magma ocean. We investigate how the geodynamic regime of GJ 486b is influenced by different surface temperature contrasts by varying possible atmospheric circulation regimes. We also investigate how the strength of the lithosphere affects the convection pattern. We find that hemispheric tectonics, the surface expression of degree‐1 convection with downwellings forming on one hemisphere and upwelling material rising on the opposite hemisphere, is a consequence of the strong lithosphere rather than surface temperature contrast. Anchored hemispheric tectonics, where downwellings und upwellings have a preferred (day/night) hemisphere, is favored for strong temperature contrasts between the dayside and nightside and higher surface temperatures. Plain Language Summary: The tectonic processes occurring on super‐Earths, which are rocky exoplanets with masses exceeding that of Earth, may differ significantly from those observed on the terrestrial planets in our solar system. Many super‐Earths are also expected to be tidally locked to their host star, so that always the same hemisphere faces the star. Tidal locking can lead to a strong temperature contrast between the dayside and nightside surface. Here, we investigate the influence of such strong surface temperature contrasts on the interior dynamics and tectonic behavior of super‐Earth GJ 486b, which is one of the best characterized Earth‐mass planets to date. We determined the surface temperature contrast between the dayside and nightside by assuming different efficiencies of atmospheric heat transport and ran global climate models for a set of different atmospheric compositions. Our 2D mantle convection simulations reveal that hemispheric tectonics, where cold material sinks on one hemisphere and hot material rises on the other side, emerges regardless of the surface temperature contrast if the planet has a strong lithosphere. However, a significant surface temperature contrast and an overall higher surface temperature tend to anchor the sinking cold material and rising hot material to the dayside and nightside respectively. Key Points: The mantle dynamics of super‐Earth GJ 486b are governed by the strength of the lithosphere and the day‐night surface temperature contrastDegree‐1 convection is a consequence of the strong lithosphere, rather than the temperature contrast between the dayside and nightsideA strong surface temperature contrast between the dayside and nightside can anchor downwellings to one hemisphere [ABSTRACT FROM AUTHOR]

In this work, we investigated the seasonal cycle of atmospheric potential oxygen (APO), a unique tracer of air‐sea gas exchanges of molecular oxygen (O2) and carbon dioxide (CO2), expressed as APO = O2 + 1.1 × CO2. APO data were obtained from flask air samples collected since the late 1990s at three Japanese ground stations and on commercial cargo ships sailing between Japan and Australia/New Zealand, North America, and Southeast Asia. We also analyzed the APO spatial distribution and seasonal cycles with simulations from an atmospheric transport model using climatological oceanic O2 fluxes from an empirical product that relate O2 flux to ocean heat as input. Model simulations reproduced the observed APO seasonal cycles generally well, but with larger amplitudes and earlier occurrence of seasonal minima and maxima than in the observations. Moreover, the observed seasonal cycles exhibited larger APO enhancements than the simulations in autumn and early winter, especially in the North Pacific at 20°N–60°N. These enhancements remained when refining the comparison by adjusting the simulated APO peak‐to‐peak amplitudes and seasonal phases to the observations. This suggests additional O2 emissions in the North Pacific, not well expressed in the air‐sea O2 fluxes used as input for our model simulations. The average autumn enhancement at 40°N–60°N was approximately twice that measured at 20°N–40°N. Confirming previous studies, our results indicate two distinct mechanisms possibly contributing to the additional oceanic O2 emissions: outgassing from a subsurface shallow oxygen maximum at 20°N–40°N and autumn phytoplankton bloom at 40°N–60°N. Plain Language Summary: Seasonal variations of air‐sea molecular oxygen (O2) exchanges are mainly driven by spring/summer emission and autumn/winter absorption. Emission results mainly from O2 production by phytoplankton at the ocean surface; absorption is related to O2 uptake in deep oxygen‐depleted water layers caused by oceanic ventilation. A phytoplankton bloom in autumn and outgassing from water rich in dissolved O2 just below the mixed layer, known as the shallow oxygen maximum, have been suggested as possible mechanisms contributing to the O2 seasonal cycles. Unfortunately, these oceanic autumn O2 emissions are not well characterized. In this study, we analyzed air samples collected in the western and northern Pacific to evaluate the oceanic component of the O2 seasonal cycle, known as "atmospheric potential oxygen" and calculated as the sum of atmospheric O2 and carbon dioxide. By comparing these observations with model simulations that used previous air‐sea O2 flux estimates as input, we identified marked enhancements in autumn at latitudes between 20°N and 60°N in the Pacific. This corresponds to the geographic area where the autumn phytoplankton bloom and the shallow oxygen maximum occur. This result is a strong indication of additional autumn O2 emissions in the extratropical North Pacific. Key Points: We analyzed atmospheric potential oxygen (APO), a tracer of air‐sea exchanges of molecular oxygen (O2) and carbon dioxide, in the PacificThe observed seasonal APO enhancement at 20°N–60°N in autumn, relative to model simulations, suggests additional oceanic O2 emissionsOutgassing from a shallow oxygen maximum (20–40°N) and an autumn phytoplankton bloom (40–60°N) likely contribute to this enhancement [ABSTRACT FROM AUTHOR]

Atmospheric rivers (ARs) are known to produce both beneficial and extreme rainfall, leading to natural hazards in Chile. Motivated to understand moisture transport during AR events, this study performs a moisture budget analysis along 50 zonally elongated ARs reaching the western coast of South America. We identify the convergence of moist air masses of tropical/subtropical origin along the AR as the primary source of vertically integrated water vapor (IWV). Over the open ocean, moisture convergence is nearly balanced by precipitation. The advection of moisture along the AR, although smaller compared to mass convergence, significantly increases toward the landfalling region. The near conservation of IWV over the open ocean, observed by tracking a Lagrangian atmospheric column along the ARs, is the explanation behind the seemingly tropical origin of ARs in time‐lapse visualizations of IWV. Plain Language Summary: Imagine atmospheric rivers (ARs) as massive, flowing rivers in the sky, but instead of water, they carry vapor from the ocean. When these "sky rivers" travel and hit the Andes Mountains in South America, they can cause a lot of rain and snow to fall. This precipitation is often good because it helps fill reservoirs and water crops. However, sometimes there's too much rain, leading to floods and landslides, which can be dangerous. Over the ocean, the amount of water vapor these atmospheric rivers pick up is almost exactly balanced by the rain that falls from them. As these atmospheric rivers get closer to South America, the movement of moisture along the river, though generally less significant than the gathering of moist air, becomes more pronounced. This means that as the atmospheric river approaches the land, it starts carrying more moisture toward its destination. We were able to see this process in action by following a moving "slice" of the atmosphere (a Lagrangian atmospheric column) as it travels along the path of the atmospheric river. This helped us understand how atmospheric rivers maintain their water content as they move. It also shows why atmospheric rivers seem to originate from tropical areas when we look at them in time‐lapse images of water vapor. Key Points: We calculate the moisture transport budget of 50 events of zonal atmospheric rivers over the Pacific that reach South AmericaHorizontal convergence of tropical and subtropical air masses act to maintain atmospheric rivers over the ocean while advection dominates near the coastFollowing a Lagrangian column, precipitable water is roughly conserved along atmospheric rivers, except near landfalling [ABSTRACT FROM AUTHOR]

Anthropogenic CO2 emission reduction strategies depend on how well we track emission enhancements at the urban scale. The estimation system, based on inverse modeling, relies on our knowledge of atmospheric transport and prior flux distributions. Hence, the analysis framework must account for uncertainties associated with each component in order to interpret the variations in observed CO2. Using an ensemble of simulations, we quantify the uncertainties in simulating anthropogenic CO2 mixing ratio enhancements at 15 locations in India. Differences in the representation of transport mechanisms and prior emission in the forward model induce a consistently large model spread of 62.2% and 41.9%, respectively, in the simulated mixing ratio over cities. The analysis reports an average uncertainty of 2.2 ppm with a maximum of 8 ppm for representing diurnally averaged anthropogenic CO2 enhancement. Diurnal variations in emissions and transport induce a rectification effect in those enhancements. The outcome of this study can thus inform future atmospheric CO2 inversion modeling at an urban scale on the expected forward model uncertainties, which are the essential components in the Bayesian inversion framework, typically lacking in the Indian region. The first‐order inversion experiments show that the change in the transport model induces significant uncertainty (up to 84.9%) in anthropogenic CO2 flux estimation at the national scale. Hence, the confidence level of inverse‐based emission estimation in India depends considerably on the accuracy of atmospheric transport modeling. Plain Language Summary: India has pledged in Paris Agreement to significantly reduce its carbon emission by 2030 to combat the adverse effects of climate change. To attain the above goal, we need an improved and detailed understanding of carbon source‐sink distribution. Further, the urban emission reduction strategies call for city‐scale CO2 enhancement tracking. We can address this vital requirement by the combined use of atmospheric trace gas measurements and CO2 simulations via inverse modeling. Atmospheric inverse modeling relates the concentration of trace gases with the underlying surface fluxes and improves our existing knowledge about emissions. Using a multitude of simulations with different initial conditions and data inputs, this study shows that the details of how atmospheric transport is modeled in the inverse modeling system have a larger influence on the national carbon budget estimation than the prior assumptions of surface flux distribution over India. The transport errors cause a significant uncertainty of up to 84.9% in carbon emission estimates. Incorporating the temporal variability of prior emission estimates in the model enables us to better understand the dilution of the anthropogenic CO2 in certain conditions. The inferences from this study can be helpful in designing an urban CO2 emission monitoring system in India. Key Points: Anthropogenic urban CO2 enhancements and their uncertainties are quantified for the Indian region using Lagrangian ensemble simulationsThe model bias can be as high as 8 ppm in predicting daily anthropogenic CO2 enhancements in Indian citiesThe transport model errors alone cause a significant uncertainty of up to 84.9% in the Indian anthropogenic CO2 flux estimates [ABSTRACT FROM AUTHOR]

A new full model of the atmospheric transport of cosmogenic 10Be is presented based on the specialized SOCOL‐AERv2‐BE chemistry‐climate model coupled with the CRAC:10Be isotope production model. The model includes all the relevant atmospheric processes and allows computing the isotope concentration at any given location and time. The full model is directly compared with 10Be isotope measurements in five Antarctic and Greenland ice cores for the period 1980–2007. The model reasonably well reproduces the average concentration and solar‐cycle dependency or the lack of it for most observational sites but does not perfectly catch the interannual variability at sites with complex orography likely due to the coarse model grid. This implies that the model correctly reproduces the large‐scale atmospheric dynamics but effectively averages out synoptic‐scale variability. It is found that the dominant source of 10Be is located in the middle stratosphere (25–40 km), in the tropical (<30° latitudes) and polar (>60°) regions, as produced by galactic cosmic rays and solar energetic particles, respectively. It is shown that >60% (90%) of 10Be produced in the atmosphere reaches the Earth's surface within one (two) years, respectively. For practical purposes, a simple parameterization of the full‐model results is presented which agrees with the full model within 20% in polar regions. This parameterization allows one to make a quick estimate of near‐ground 10Be concentrations based only on production rates without heavy calculations. This practical approach can be applied to studies of solar and geomagnetic variability using cosmogenic isotopes. Key Points: A full model of production and atmospheric transport of 10Be produced by galactic cosmic ray (GCR) and solar energetic particles (SEP) is presented and validatedThe dominant source regions of 10Be in polar ice are identified as tropical and polar stratosphere for GCR and SEPs, respectivelyAn easy‐to‐use parameterization of the full model is proposed to study cosmic‐ray variability with 10Be data [ABSTRACT FROM AUTHOR]

We investigate the role of ocean heat transport (OHT) in driving the decadal variability of the Arctic climate by analyzing the pre‐industrial control simulation of a high‐resolution climate model. While the OHT variability at 65°N is greater in the Atlantic, we find that the decadal variability of Arctic‐wide surface temperature and sea ice area is much better correlated with Bering Strait OHT than Atlantic OHT. In particular, decadal Bering Strait OHT variability causes significant changes in local sea ice cover and air‐sea heat fluxes, which are amplified by shortwave feedbacks. These heat flux anomalies are regionally balanced by longwave radiation at the top of the atmosphere, without compensation by atmospheric heat transport (Bjerknes compensation). The sensitivity of the Arctic to changes in OHT may thus rely on an accurate representation of the heat transport through the Bering Strait, which is difficult to resolve in coarse‐resolution ocean models. Plain Language Summary: We studied how ocean heat transport (OHT) affects decade‐timescale variability in the Arctic climate using a high‐resolution climate model. Specifically, we compared the impacts of heat entering the Arctic Ocean through the Nordic Seas from the Atlantic and through the Bering Strait from the Pacific. Though more heat is transported from the Atlantic, Arctic surface temperature and sea ice respond more strongly to changes in OHT through the Bering Strait. Unlike Atlantic OHT, changes in Bering Strait OHT impact local air temperatures directly, without compensating changes in atmospheric heat transport. Proper representation of the Arctic's sensitivity to future increased OHT may thus rely on correctly representing OHT through Bering Strait, which is challenging in coarse‐resolution ocean models. Key Points: Ocean heat transport variability through the Bering Strait has an outsized effect on Arctic sea ice cover and surface temperatureAtlantic ocean heat transport anomalies into the Arctic are compensated by atmospheric heat transport anomalies on decadal timescales [ABSTRACT FROM AUTHOR]

Various fire emission estimates for southern Africa during 2019, derived with multiple burned area data sets with resolutions ranging from 500 to 20 m, are evaluated using satellite carbon monoxide (CO) observations. Southern African emissions derived from burned area generated by 20 m Sentinel‐2 satellite imagery are up to 120% higher than other estimates because small fires are better detected with a higher‐resolution satellite instrument. A comprehensive comparison between simulated and observed atmospheric CO indicates that the Sentinel‐2 burned area data significantly improves emission estimates, with up to 15% reduction in CO concentration biases in comparison to emissions based on coarser resolution burned area data. We also found that the temporal lag between emissions and atmospheric CO concentrations during the peak fire month was related to atmospheric transport. These findings emphasize the importance of utilizing higher‐resolution satellite instruments in accurately estimating emissions and understanding the impact of small fires on global climate. Plain Language Summary: We studied how much carbon monoxide (CO) was released into the air in southern Africa due to fires. To derive CO emissions we used different remotely sensed data of area burned, with varying levels of detail, from 500 to 20 m, and used these emissions in a model to mimic atmospheric transport and chemistry of CO. We found that emissions derived from the very detailed 20‐m satellite images from Sentinel‐2 produced a similar large amount of CO in the atmosphere over southern Africa as seen by CO satellite observations. This is because the smaller fires, which are harder to spot, were detected with the 20‐m burned area satellite observations. We also found that the air movement and inflow of polluted air from outside Africa impacted the peak of air pollution. Key Points: Sentinel‐2 burned area detects small fires, resulting in up to 120% higher fire emissions compared to conventional resolution estimatesImproved fuel load modeling and new emission factors yield more trustworthy fire emissions that can be evaluated with top‐down constraintsAtmospheric modeling and TROPOMI CO observations indicate a 15% bias reduction using Sentinel‐2 burned area compared with coarser fire data [ABSTRACT FROM AUTHOR]

Rising Arctic temperatures pose a threat to the large carbon stores trapped in Arctic permafrost. To assess methane emissions in high‐Arctic regions, we analyzed atmospheric data from Alaska and Siberia using two methods: (a) a wind sector approach to calculate emission changes based on concentration enhancements using wind direction, and (b) an inversion method utilizing a high‐resolution atmospheric transport model. Incorporating data after 2015, we observed a significant rise in methane emissions (0.018 ± 0.005 Tg yr−2 from 2000 to 2021) from Alaska's North Slope, indicating a shift from previous analyses. We find 34%–50% of yearly emissions occurred in the late season (September–December) consistently across multiple years and regions, which is historically underestimated in models and inventories. Our findings reveal significant changes occurring in the Arctic, highlighting the crucial role of long‐term atmospheric measurements in monitoring the region, especially during the cold season. Plain Language Summary: The Arctic is undergoing dramatic changes with temperatures increasing at four times the global average. This increase in temperature threatens to thaw the large stores of frozen carbon in Arctic soils which can be released as methane, a more potent greenhouse gas than carbon dioxide. We use measurements of methane in the atmosphere from four Arctic Ocean coastal stations to quantify emissions from the surface. We find that emissions from the North Slope of Alaska have been increasing over the past three decades, which reflects a change from previous analyses. Additionally, we show large and consistent emissions from September to December across multiple Arctic regions. This season has traditionally been underestimated in global methane budgets and providing accurate methane quantification is vital for climate change mitigation. Our results show that important change is occurring in the Arctic, and long‐term atmospheric data can be used to monitor this change, particularly in the cold season. Key Points: Increasing tundra methane emissions from the Alaskan North Slope from 1986 to 2021 are now detected through long‐term atmospheric measurementsEmissions from the late season (September–December) are found to be persistent across multiple years and from three high Arctic regionsLate season underestimation of emissions in models and inventories is attributed to an underestimation of the emitting area [ABSTRACT FROM AUTHOR]

Atmospheric Rivers (ARs) are synoptic‐scale conduits for poleward transport of heat and water, often associated with extreme rainfall. Using NASA surface heat flux observations and climate model simulations, we assess whether ARs are "rivers", transporting heat and moisture over longer distances, or mostly local convergence. The observations indicate that ARs reduce extratropical surface energy fluxes, even during early development. This damping of surface fluxes during ARs is also simulated in the Goddard Institute for Space Studies ModelE, 2.1 (GISS‐E2.1) nudged to (MERRA2) reanalysis winds. Furthermore, water provenance tracers in GISS‐E2.1 identify the moisture source for ∼7,500 ARs globally during 2018–2022 as farther upstream and equatorward compared to climatology. These results quantitatively show that ARs source relatively less moisture from the surface beneath them and more from a greater distance than during non‐AR times. Plain Language Summary: Atmospheric rivers are thin, river‐like, streams of moisture connecting the mid‐ and high‐latitudes to the tropics, often associated with extratropical storms. These events are regions that have large amounts of moisture and can generate heavy precipitation. We show that moisture and energy fueling the ARs do not come from the ocean directly beneath the ARs. First, we use a dataset derived from satellite retrievals of surface winds to demonstrate that the energy transferred into ARs from the ocean are weaker than usual during AR events. Then we use a global climate model to show that the origins of the moisture in the ARs arrives via atmospheric transport from regions outside of the ARs, farther away and nearer to the equator. Key Points: When atmospheric rivers form, ocean fluxes are reduced, pulling in moisture from farther away than during non‐atmospheric river eventsAfter formation, atmospheric rivers decrease surface heat fluxes from the ocean into the atmosphereAtmospheric rivers source moisture from ∼10° equatorward of non‐atmospheric rivers [ABSTRACT FROM AUTHOR]

The Intertropical Convergence Zone (ITCZ) has an annual mean location north of the equator today. The factors determining this location and the evolution to its modern state are actively debated. Here we investigate how the Atlantic Meridional Overturning Circulation (AMOC) influences the ITCZ during the early‐to‐middle Miocene. By conducting a sensitivity study with an open Canadian Arctic Archipelago gateway, we show that North Atlantic Deep‐Water formation strengthens the AMOC, in alignment with Miocene North Atlantic ventilation proxies. A vigorous AMOC increases northward Atlantic Ocean heat transport and cross‐equatorial atmospheric energy transport shifts southwards to compensate, pushing the ITCZ northwards. Our study supports AMOC development as a strong contributor to the ITCZ's northern location today. Existing proxy‐based interpretations of ITCZ history are too sparse to strongly confirm these results. We predict a strong in‐phase relationship between AMOC strength and ITCZ's northward location, which should be testable in high resolution paleoclimate records. Plain Language Summary: The Intertropical Convergence Zone (ITCZ) is a narrow tropical region where tropical rainfall is concentrated. Its annual mean position is predominantly north of the equator in the modern climate, especially in the Atlantic and eastern Pacific oceans. The position of the ITCZ varies seasonally and over long‐time scales. One hypothesis is that Atlantic Meridional Overturning Circulation (AMOC) energy transport displaces the ITCZ north of the Equator. We test this hypothesis in a paleoclimate simulation with realistic early‐to‐middle Miocene (20–11.6 million years ago) configurations. By opening the Canadian Arctic Archipelago gateway, a crucial connection between the Arctic Ocean and North Atlantic, we find that a strong AMOC transports more heat northward in the ocean, and in compensation, the flow of atmospheric energy across the equator shifts southward, consequently pushing the ITCZ north of the equator. More Miocene proxy records are required to empirically support this model result. Key Points: Opening an Arctic Ocean gateway in Miocene climate simulations generates a strong Atlantic Meridional Overturning Circulation (AMOC) and increases northward ocean heat transportTo compensate, atmospheric energy transport across the equator shifts southward, pushing the Intertropical Convergence Zone (ITCZ) north of the equatorAMOC strengthening is a mechanism in past warm climates for northward ITCZ shifts [ABSTRACT FROM AUTHOR]

A linear non‐diffusive algorithm for advective transport is developed that greatly improves the detail at which aerosols and clouds can be represented in atmospheric models. Linear advection schemes preserve tracer correlations but the most basic linear scheme is rarely used by atmospheric modelers on account of its excessive numerical diffusion. Higher‐order schemes are in widespread use, but these present new problems as nonlinear adjustments are required to avoid occurrences of negative concentrations, spurious oscillations, and other non‐physical effects. Generally successful at reducing numerical diffusion during the advection of individual tracers, for example, particle number or mass, the higher‐order schemes fail to preserve even the simplest of correlations between interrelated tracers. As a result, important attributes of aerosol and cloud populations including radial moments of particle size distributions, molecular precursors related through chemical equilibria, aerosol mixing state, and distribution of cloud phase are poorly represented. We introduce a new transport scheme, minVAR, that is both non‐diffusive and preservative of tracer correlations, thereby combining the best features of the basic and higher‐order schemes while enabling new features such as the tracking of sub‐grid information at arbitrarily fine scales with high computational efficiency. Plain Language Summary: A long‐standing challenge for the representation of aerosols and clouds in atmospheric models is to properly transport particles in space using higher‐order advection schemes. These schemes have less numerical diffusion than the simple basic scheme, but cannot maintain the physical relationship between particle number and mass that needs to be simulated correctly for better understanding of aerosol‐cloud‐turbulence interactions either in a laboratory‐scale cloud chamber or at larger atmospheric scales. The present advection scheme (minVAR, short for minimum variance) introduces a diffusion limiter, under the idea that achieving minimal spatial variance on an Eulerian grid implies maximal resolution and—it turns out ‐ complete elimination of numerical diffusion. By preserving tracer correlations and eliminating numerical diffusion, minVAR includes the best features of the simple basic and higher‐order schemes. This innovation resolves the two‐moment limitation, a necessary first step toward the high‐fidelity, multi‐moment, multi‐scale representation of aerosols and clouds in atmospheric models. Moments, because they are so strongly and nonlinearly correlated, provide an excellent example of correlation failure and serve to focus the present study. That said, there is no reason to suggest that the methods developed here would be inapplicable to other correlated tracer sets. Key Points: A diffusion limiter—minVAR—was added to the linear basic advection scheme and found to eliminate numerical diffusion completelyThe minimum variance property of minVAR makes the new method optimal for advection of independent tracers as well as correlated onesminVAR establishes a unique one‐to‐one correspondence between points along a Lagrangian trajectory and their mapping to the Eulerian grid [ABSTRACT FROM AUTHOR]

We present a two‐dimensional, zonally averaged global model of atmospheric transport named MALTA: Model of Averaged in Longitude Transport in the Atmosphere. It aims to be accessible to a broad community of users, with the primary function of quantifying emissions of greenhouse gases and ozone depleting substances. The model transport is derived from meteorological reanalysis data and flux‐gradient experiments using a three‐dimensional transport model. Atmospheric sinks are prescribed loss frequency fields. The zonally averaged model simulates important large‐scale transport features such as the influence on trace gas concentrations of the quasi‐biennial oscillation and variations in inter‐hemispheric transport rates. Stratosphere‐troposphere exchange is comparable to a three‐dimensional model and inter‐hemispheric transport is faster by up to 0.3 years than typical transport times of three‐dimensional models, depending on the metric used. Validation of the model shows that it can estimate emissions of CFC‐11 from an incorrect a priori emissions field well using three‐dimensional (3D) mole fraction fields generated using a different 3D model than which the flux gradient relationships were derived. The model is open source and is expected to be applicable to a wide range of studies requiring a fast, simple model of atmospheric transport and chemical processes for estimating associated emissions or mole fractions. Plain Language Summary: We introduce a simplified global model that simulates the movement of gases in the atmosphere. The main goal of this model is to understand how greenhouse gases and substances that deplete the ozone layer are transported and distributed, and to more accurately estimate their global emissions using concentrations measured in the atmosphere over time. To achieve this, the model uses data from weather analysis and experiments conducted with a more complex three‐dimensional model. The model calculates how gases move across different latitudes and altitudes, and accounts for their chemical loss. The simplified model can accurately reproduce large‐scale atmospheric transport phenomena. The model is publicly available. We expect it to be useful for research that requires a fast and easy to use model to understand large‐scale atmospheric transport and related processes. Key Points: A user‐friendly 2D global atmospheric transport model using transport derived from 3D reanalysis data and flux‐gradient experimentsIntended for use with long‐lived greenhouse gases and ozone‐depleting substancesAn open‐source model, which is applicable to diverse studies on emissions and chemical processes [ABSTRACT FROM AUTHOR]

The Cambro‐Ordovician interval marks a significant transition from extinction to bio‐diversification in deep time. However, the relationship of bio‐transition to volcanism, commonly characterized by mercury (Hg) systematics in sedimentary records, has not been examined. We present the first Cambro‐Ordovician Hg systematics from the Scandinavian Alum Shale. Our results show pronounced Furongian Hg enrichments, coupled with positive Δ199Hg, Δ200Hg, and Δ201Hg values and negative Δ204Hg values that we ascribe to atmospheric Hg transport over long‐distances, while Early Ordovician Hg anomalies, characterized by near‐zero mass‐independent isotope values, indicative of submarine source. Our findings are supported by two new proxies: molybdenum‐Hg and vanadium‐δ202Hg co‐variations, demonstrating Hg systematics were strongly influenced by changes in source and depositional conditions. Constrained by a synchronous atmospheric‐tectonic‐oceanic model, we hypothesize Furongian subaerial volcanism contributed to global extinction and oceanic anoxia, whereas Early Ordovician submarine volcanism concurrent with ocean water upwelling promoted the nascent bio‐diversification. Plain Language Summary: The late Cambrian‐Early Ordovician interval is a crucial time that bridges the Cambrian extinction and Great Ordovician Bio‐diversification events. The former is associated with 50% decrease in genera, whereas the latter displays threefold increase in species. Volcanism is associated with extinction and bio‐development events throughout Earth's history. Prior works investigated potential biogeochemical controls that could have supported the Cambro‐Ordovician bio‐transition, but none explored the role of volcanism. We, for the first time, examine Hg abundance ratios and isotopes in the Scandinavian Alum Shale core across this boundary. Two novel molybdenum‐Hg and vanadium‐δ202Hg models are proposed to improve our interpretation of the geochemical records about the effects of volcanism on environmental changes during this enigmatic transition. Constrained by a synchronous atmospheric‐oceanic‐tectonic model, our results demonstrate that late Cambrian subaerial volcanism contributed to oceanic anoxia and extinction, whereas Early Ordovician submarine volcanism and water upwelling led to the subsequent bio‐radiation. Key Points: Mercury is associated with organic matter in carbonaceous Alum shale deposited under sulfidic conditionsLate Cambrian‐Early Ordovician mercury was released by volcanism that also triggered major environmental changeMercury mass independent fractionation isotopes suggest late Cambrian subaerial volcanism but Early Ordovician submarine source [ABSTRACT FROM AUTHOR]

The observed partitioning of poleward heat transport between atmospheric and oceanic heat transports (AHT and OHT) is compared to that in coupled climate models. Model ensemble mean poleward OHT is biased low in both hemispheres, with the largest biases in the Southern Hemisphere extratropics. Poleward AHT is biased high in the Northern Hemisphere, especially in the vicinity of the peak AHT near 40°N. The significant model biases are persistent across three model generations (CMIP3, CMIP5, CMIP6) and are insensitive to the satellite radiation and atmospheric reanalyzes products used to derive observational estimates of AHT and OHT. Model biases in heat transport partitioning are consistent with biases in the spatial structure of energy input to the ocean and atmosphere. Specifically, larger than observed model evaporation in the tropics adds excess energy to the atmosphere that drives enhanced poleward AHT at the expense of weaker OHT. Plain Language Summary: The equator‐to‐pole contrast of solar radiation entering the climate system drives the large‐scale oceanic and atmospheric circulations that, in turn, move heat from the equator to the poles to moderate latitudinal temperature contrasts. The ocean moves the majority of heat in the tropics whereas the atmosphere moves the vast majority of heat in the mid‐ and polar‐latitudes. We demonstrate that, on average, state‐of‐the‐art climate models representing both oceanic and atmospheric circulations simulate too little oceanic heat transport and too much atmospheric heat transport relative to observational estimates. These model biases in the atmosphere‐ocean partitioning of poleward heat transport are persistent across three generations of climate model ensembles spanning 20 years of progress in climate modeling and are insensitive to the choice of datasets used to calculate observed heat transports. The model biases are consistent with stronger than observed surface evaporation in the tropics which enhances atmospheric heat transport at the expense of oceanic heat transport. Key Points: Climate models simulate too little poleward oceanic heat transport and too much poleward atmospheric heat transport in the extratropicsModel biases in heat transport partitioning are persistent across model generation and are insensitive to the observational data sets usedStronger than observed evaporation in models enhances atmospheric heat transport at the expense of oceanic heat transport [ABSTRACT FROM AUTHOR]

Extreme climate events are becoming more frequent, with poorly understood implications for carbon sequestration by terrestrial ecosystems. A better understanding will critically depend on accurate and precise quantification of ecosystems responses to these events. Taking the 2019 US Midwest floods as a case study, we investigate current capabilities for tracking regional flux anomalies with "top‐down" inversion analyses that assimilate atmospheric CO2 observations. For this analysis, we develop a regionally nested version of the NASA Carbon Monitoring System‐Flux system for North America (CMS‐Flux‐NA) that allows high resolution atmospheric transport (0.5° × 0.625°). Relative to a 2018 baseline, we find the 2019 US Midwest growing season net carbon uptake is reduced by 11–57 TgC (3%–16%, range across assimilated CO2 data sets). These estimates are found to be consistent with independent "bottom‐up" estimates of carbon uptake based on vegetation remote sensing (15–78 TgC). We then investigate current limitations in tracking regional carbon budgets using "top‐down" methods. In a set of observing system simulation experiments, we show that the ability of atmospheric CO2 inversions to capture regional carbon flux anomalies is still limited by observational coverage gaps for both in situ and satellite observations. Future space‐based missions that allow for daily observational coverage across North America would largely mitigate these observational gaps, allowing for improved top‐down estimates of ecosystem responses to extreme climate events. Plain Language Summary: Extreme climate events, such as floods or heatwaves, can have major impacts on the carbon cycle. For example, widespread flooding in the US Midwest during 2019 delayed the planting of crops leading to reduced plant growth and carbon uptake relative to 2018. Here, we test how well this reduction in carbon uptake can be inferred from measurements of atmospheric CO2. We find that these data can identify reduced net carbon uptake to the US Midwest during the 2019 floods, but that sparse observational coverage limits our ability to quantify the anomaly in net carbon uptake. We show that expanded space‐based observations of CO2 would fill these gaps, allowing for improved estimates of interannual variations in the US CO2 budget. Key Points: Bottom‐up and top‐down methods capture reduced 2019 US Midwest carbon uptake relative to 2018Gaps in atmospheric CO2 observations drive uncertainties in top‐down estimatesNested inversion better localizes US Midwest ΔNEE relative to coarse global model [ABSTRACT FROM AUTHOR]

The 10Be record in laminated travertines is a potential proxy for reconstructing past solar activity down to the annual scale; however, correcting for the potential influence of climatic or environmental variations remains challenging. Here, we present an annually resolved 10Be record using travertines from Baishuitai, China, covering the period from 1510 to 1701 CE, along with environmental proxies, to evaluate climatic influences and implement corrections to accurately reconstruct solar activity. We demonstrate that the 10Be deposition in travertines exhibits two environmental impacts: the transport efficiency of atmospheric 10Be into travertine and the additional 10Be inflow from overland flow associated with rainfall. We show that these impacts can be corrected based on iron and potassium contents. The resulting corrected record agrees with ice‐core and tree‐ring records, demonstrating the feasibility of using such carbonate sediment 10Be records to reconstruct past solar activity. Plain Language Summary: The travertine 10Be record has great potential as a proxy for high‐resolution reconstruction of past solar activity; however, the methodology for correcting the potential influence of climatic or environmental variations has not been fully established. This study presents a new high‐precision annual 10Be record using travertines from Baishuitai, China, covering the period 1510–1701 CE, together with records of environmental proxies, allowing us to evaluate the climatic influences and establish a methodology for correcting them to facilitate accurate solar activity reconstruction. We find that there are two environmental impacts on the deposition of 10Be in travertine: one is the transport efficiency of atmospheric 10Be into travertine, and the other is the additional 10Be inflow from the runoff following rainfall events, and we use iron (Fe) and potassium (K) contents to correct these impacts. The corrected travertine 10Be record exhibits good agreement with ice‐core 10Be and tree‐ring 14C records, supporting that the 10Be record in Baishuitai travertine reliably reflects the atmospheric radionuclide production rate as regulated by solar activity. This result demonstrates the feasibility of using such carbonate sediment 10Be records to reconstruct annual solar activity and suggests the possibility of extending the annual records further back in time than previously obtained. Key Points: A high‐precision annual record of travertine 10Be from 1510 to 1701 CE was obtained to assess its potential as a proxy for solar activityClimatological and environmental impacts on 10Be deposition were found to be correctable based on the content of trace elementsThe travertine 10Be record corrected for climatological impacts reasonably preserves the decadal and centennial‐scale solar cycles [ABSTRACT FROM AUTHOR]

The Carrington event of 1859 has been the strongest solar flare in the observational history. It plays a crucial role in shedding light on the frequency and impacts of the past and future Solar Energetic Particle (SEP) events on human societies. We address the impact of the Carrington event by measuring tree‐ring 14C with multiple replications from high‐latitude locations around the event and by comparing them with mid‐latitude measurements. A transient offset in 14C following the event is observed with high statistical significance. Our state‐of‐the‐art 14C production and transport model does not reproduce the observational finding, suggesting features beyond present understanding. Particularly, our observation would require partially fast transport of 14C between the stratosphere and troposphere at high latitudes. The observation is consistent with the previous findings with the SEP events of 774 and 993 CE for which faster integration of 14C into tree rings is observed at high latitudes. Plain Language Summary: Strong Earth‐directed solar eruptions can cause 14C concentration spikes in the atmosphere. Large enough events may leave a signal in the annually grown tree‐rings as they capture the isotopic carbon fingerprint through photosynthesis. Such rapid 14C increases have been detected, for instance, starting in years 774 and 993 CE. However, no increase has been observed following the Carrington event of 1859, despite it being the largest solar eruption of the modern era. Notably, all prior 14C measurements covering the Carrington event come from mid‐latitude trees. To achieve a broader geographical coverage, we have measured the event from several high‐latitude locations. After comparing the high‐ and mid‐latitude measurements, we have found a statistically significant difference lasting for several years post‐Carrington. To better understand the difference, we have adopted a 14C production and atmospheric transport model capable of simulating regional differences. Despite the improved model, we found it unable to reproduce the observational results, which suggests features beyond current understanding. Ultimately, the observation emphasizes the role of subtle 14C differences in tree‐ring 14C studies, potentially opening new ways to study past solar phenomena and atmospheric dynamics. Key Points: A transient offset in 14C from high‐latitude Finnish Lapland tree rings was observed between years 1861 and 1863The Carrington event and the stratosphere‐troposphere dynamics are discussed as potential explanations for the disparityThe discovery underscores the importance of transient offsets, high‐latitude tree rings in spotting anomalous solar/geomagnetic phenomena [ABSTRACT FROM AUTHOR]

The physicochemical properties and origins of atmospheric aerosols in the Tibetan Plateau (TP) region are a research topic of great interest, but an in‐depth understanding of this topic is challenging, partially due to a lack of intensive in situ observations. Thus, a field campaign was conducted over Yadong, a remote area on the south slope of the TP from June 11 to 31 August 2021. The aerosol loading was low, with a black carbon mass concentration of 147.4 ± 98.4 ng·m−3. Aerosol single‐scattering albedo was low (0.73 ± 0.11 at 550 nm) and increased from 450 to 700 nm wavelength. Organic matter (OM) accounting for 69.6% of the total aerosol mass and relatively high secondary organic carbon ratios, highlighting the importance of secondary formation. An interesting phenomenon observed was that the evolution of aerosols was mainly characterized by diurnal variation, which could not be explained by large‐scale atmospheric processes such as Indian summer monsoon. Instead, it was found that regional mountain‐valley winds between the Himalayas and South Asia transported polluted air masses toward the TP, especially in the afternoon when regional valley wind are expected to be the strongest and the boundary layer in South Asia is deepest. Additionally, daytime local valley wind further elevated these aerosols to higher altitudes on the TP. This paper provides insights into the transport mechanisms of aerosols from South Asia to the TP. These findings are of great importance since aerosols exhibit significant diurnal variations in the TP region. Plain Language Summary: Previous studies focused on the analysis of the physical or chemical properties of aerosols on the Tibetan Plateau, but this study provides a comprehensive examination of both. The findings reveal that aerosols on the southern slope of the Tibetan Plateau exhibit strong absorption efficiency. Aerosol single‐scattering albedo was low (0.73 ± 0.11 at 550 nm), which may be attributed to aerosol secondary generation and coating. Finally, the mechanism of pollutant transport from South Asia to the Tibetan Plateau was analyzed relies on site observations, satellite, and reanalysis data to highlight the link between diurnal variations of pollutants and transport mechanism. The specific transport mechanism be understood uniformly across different scales, including Indian summer monsoon, regional mountain‐valley winds between the Himalayas and South Asia, and local mountain‐valley winds circulation. Key Points: Aerosol single‐scattering albedo was low (0.73 ± 0.11 at 550 nm) and secondary organic matter was the major aerosol componentThe evolution of aerosols was mainly characterized by diurnal variation that was related to transport mechanism over YadongThe Himalayas‐South Asia regional mountain‐valley winds combined with local mountain‐valley winds transport aerosols to the Tibetan Plateau [ABSTRACT FROM AUTHOR]

A prerequisite to applying 10Be in natural archives for solar and geomagnetic reconstructions is to know how 10Be deposition reflects atmospheric production changes. However, this relationship remains debated. To address this, we use two state‐of‐the‐art global models GEOS‐Chem and ECHAM6.3‐HAM2.3 with the latest beryllium production model. During solar modulation, both models suggest that 10Be deposition reacts proportionally to global production changes, with minor latitudinal deposition biases (<5%). During geomagnetic modulation, however, 10Be deposition changes are enhanced by ∼15% in the tropics and attenuated by 20%–35% in subtropical and polar regions compared to global production changes. Such changes are also hemispherically asymmetric, attributed to asymmetric production between hemispheres. For the solar proton event in 774/5 CE, 10Be shows a 15% higher deposition increase in polar regions than in tropics. This study highlights the importance of atmospheric mixing when comparing 10Be from different locations or to independent geomagnetic field records. Plain Language Summary: The cosmogenic radionuclide beryllium‐10 (10Be) deposition in natural archives can be used to reconstruct solar and geomagnetic changes in the past. Understanding how 10Be deposition reflects atmospheric production rate changes is crucial for these applications. However, this relationship remains debated. To address this issue, we use two state‐of‐the‐art global models, GEOS‐Chem 14.1.1 and ECHAM6.3‐HAM2.3, along with the latest beryllium production model (CRAC: Be). When responding to solar modulation, both models indicate that 10Be deposition corresponds proportionally to global production rate changes, with a minor latitudinal bias. However, during geomagnetic modulation, 10Be deposition changes significantly compared to global production rate changes. 10Be deposition also shows varying hemispheric responses to geomagnetic modulation, attributed to the asymmetric production between hemispheres. For the extreme solar proton event in 774/5 CE, 10Be shows a higher deposition flux increase in the polar regions compared to the tropics. These findings underscore the need to account for atmospheric mixing on 10Be deposition from different locations, especially for the changes due to the geomagnetic field variations. Key Points: We used two state‐of‐the‐art global models incorporating the latest beryllium production rates to study the sources of 10Be deposition10Be deposition shows strong regional bias compared to the global signal in response to geomagnetic modulation but not to solar modulation10Be deposition shows varying hemispheric responses to geomagnetic modulation, attributed to the asymmetric production between hemispheres [ABSTRACT FROM AUTHOR]

The surface air temperature (SAT) over the Sahara Desert has increased at a much faster rate than average tropical land in recent decades. This study examines the relative roles of anthropogenic greenhouse gas (GHG) forcing and sea surface temperature (SST) change in the observed Saharan temperature increase during boreal warm season from 1979 to 2020 using atmospheric general circulation model simulations. It is found that the SST forcing dominates the observed Saharan warming. Further analysis shows that the warming ocean forces the Saharan SAT increase by moving more energy to the Sahara Desert, while the water vapor feedback plays a secondary role. The reason for the stronger Saharan warming than the average tropical land given the same SST forcing is also explored. We found that the largest contributor to the warming contrast is the lapse‐rate feedback, which is attributable to the difference in the vertical warming profile. Plain Language Summary: Sahara Desert has experienced a stronger warming than the tropical land on average since 1979. Debates continue on whether the amplified Saharan warming is a response to the remote sea surface temperature (SST) change or the radiative forcing brought about by the increasing anthropogenic greenhouse gas. In this study, we quantify the relative contributions of these two forcing agents to the observed Saharan temperature increase. It is found that the observed Saharan warming is largely controlled by the remote SST forcing. As the ocean warms up, it acts to transport more energy to the Sahara Desert and warms the surface. The warming contrast between the Sahara Desert and the average tropical land is found to be dominated by the lapse‐rate feedback (LR), which favors the Saharan warming but suppresses the average tropical land warming. The difference in LR is a result of the different vertical warming structure over the Sahara Desert and average tropical land. Key Points: The observed Saharan warming since 1979 is largely a result of the sea surface temperature (SST) change rather than direct anthropogenic greenhouse gas radiative forcingThe dominant factor driving Saharan warming is the anomalous atmospheric energy transport from the warming oceanLapse rate and water vapor feedbacks both amplify Saharan warming relative to the average tropical land in response to the SST forcing [ABSTRACT FROM AUTHOR]

In the northern high latitudes, warmer spring temperatures generally lead to earlier leaf onsets, higher vegetation production, and enhanced spring carbon uptake. Yet, whether this positive linkage has diminished under climate change remains debated. Here, we used atmospheric CO2 measurements at Barrow (Alaska) during 1979–2020 to investigate the strength of temperature dependence of spring carbon uptake reflected by two indicators, spring zero‐crossing date (SZC) and CO2 drawdown (SCC). We found a fall and rise in the interannual correlation of temperature with SZC and SCC (RSZC‐T and RSCC‐T), showing a recent reversal of the previously reported weakening trend of RSZC‐T and RSCC‐T. We used a terrestrial biosphere model coupled with an atmospheric transport model to reproduce this fall and rise phenomenon and conducted factorial simulations to explore its potential causes. We found that a strong–weak–strong spatial synchrony of spring temperature anomalies per se has contributed to the fall and rise trend in RSZC‐T and RSCC‐T, despite an overall unbroken temperature control on net ecosystem CO2 fluxes at local scale. Our results provide an alternative explanation for the apparent drop of RSZC‐T and RSCC‐T during the late 1990s and 2000s, and suggest a continued positive linkage between spring carbon uptake and temperature during the past four decades. We thus caution the interpretation of apparent climate sensitivities of carbon cycle retrieved from spatially aggregated signals. [ABSTRACT FROM AUTHOR]

The heat wave in late June of 2021 (PNW21) set new temperature records in the Pacific Northwest (PNW). In Lytton the highest temperature ever recorded in Canada was measured. Several studies have already explored this extreme event in detail, however, here we compare the atmospheric air mass transport and heating processes associated with this heat wave with the 34 other most extreme heat events in the same region during the period 1960–2021, using a long backtracking time of 25 days. We found significant differences in the heat waves. During PNW21 most of the air was coming from the Philippine Sea, with more than 40% of the air located south of 15°N, and anomalous advection of sensible and latent heat from the Tropics was the dominant cause of PNW21. The latent heat was efficiently converted into sensible heat by precipitation, which was unique, as most other extremes experienced net diabatic cooling. Plain Language Summary: At the end of June in 2021 a heat wave occurred over the Pacific Northwest (PNW) and led to catastrophic damage in the region, notably the destruction of the town of Lytton by a wild fire 1 day after a new temperature record for Canada was set there. Here we look at where the air during this event was coming from and compare the atmospheric mass transport to 34 other extreme heat events in this region. We found that during the heat wave in June 2021 most of the air was coming from the Philippine Sea where it took up large amounts of heat and moisture. This source region is deeper in the Tropics than for all other extreme events. At the same time, the Philippine Sea was anomalously warm. Thus, the air was warmer and moister than for all the other extreme events already 3 weeks before reaching the PNW. The energy associated with the high tropical moisture content was efficiently converted into heat by precipitation along the Meiyu‐Baiu front—a unique process not found for any other extreme heat event. Key Points: The air causing the heat wave in late June 2021 (PNW21) came from deep in the Tropics, more south and west compared to other eventsThree weeks prior to the event, the air was warmer and moister, indicating that advection of heat from the Tropics was an important driverCondensation in a warm conveyor belt caused heating for PNW21, while most other extreme events showed overall diabatic cooling [ABSTRACT FROM AUTHOR]

Total precipitation minus evaporation (P − E) for the Atlantic is negative while it is approximately neutral for the Pacific. This has frequently been attributed to westward Atlantic‐to‐Pacific moisture flux across Central America. However, this Eulerian perspective has limited scope as it does not consider the origins of the water crossing ocean drainage basin boundaries and the possibility that it has remote sources. By using an airmass trajectory model, we take a Lagrangian approach to investigate the origin of the moisture contributing to fluxes, Qn, across these boundaries. Qn is partitioned into contributions from each basin, the stratosphere and trajectories not assigned an origin. The total Qn across each basin boundary are mainly composed of contributions from the two adjacent basins while remote or stratospheric origins make small contributions. Partitioning Qn shows that the atmosphere exports ∼1 Sv water vapor from the Atlantic, Indian and Pacific basins with a similar quantity imported to the Pacific. However, Atlantic and Indian atmospheric imports are ∼0.5–0.6 Sv. Normalizing by drainage basin perimeters reveals that the import to these basins is half as efficient as Pacific import. Partitioning P − E into contributions from other basins shows that Pacific moisture import is dominated by trajectories with Indian basin origin (∼38%, or 0.43 Sv, of total Pacific import). The import is greatest in boreal summer due to the Asian monsoon flow and stronger westward flux across Central America. These anomalies dominate the difference in annual imports between the Pacific, Atlantic and Indian basins. Plain Language Summary: Precipitation and evaporation are approximately balanced across the Pacific Ocean drainage basin while the Atlantic and Indian basins have surpluses of evaporation. This has previously been explained by strong westward atmospheric moisture transport from the Atlantic across Central America to the Pacific in the trade winds. However, this hypothesis does not account for moisture that is transported from remote sources. We have used an airmass trajectory model to calculate pathways of moisture for 14 days prior to arrival at the ocean drainage basin catchment boundaries and determine the origins of moisture crossing the boundaries then partition the cross‐boundary moisture flux into contributions from each ocean basin. We find that most of the cross‐boundary flux is explained by contributions from the two basins directly adjacent to the boundaries and remote sources are negligible in comparison. Partitioning the moisture fluxes also shows that the Atlantic, Indian and Pacific basins export similar quantities of moisture but the atmosphere imports less moisture to the Atlantic and Indian basins. Moisture with origin from the Indian basin makes up 38% of the moisture imported to the Pacific. This mainly occurs in boreal summer and shows the role of the Asian Summer Monsoon. Key Points: Airmass trajectories used to partition atmospheric moisture fluxes across catchment boundaries into ocean basins that water originates fromMoisture fluxes crossing catchment boundaries have little contribution from remote ocean basins and are dominated by the two adjacent basinsAtmospheric moisture import to the Pacific drainage basin is dominated by trajectories with Indian Ocean origin rather than Atlantic origin [ABSTRACT FROM AUTHOR]

Mineral dust is one of the most abundant types of ice nucleating particles in the atmosphere. During atmospheric transport, mineral dust particles can become coated with inorganic and organic solutes, which can impact their ice nucleation activity. Aminium cations formed from amines are one type of organic solute that can coat mineral dust particles in the atmosphere, but their effects on the ice nucleation activity of mineral dust have not been studied. We investigated the effects of primary, secondary, and tertiary aminium cations with methyl and ethyl groups, as well as ammonium cations, on the ice nucleation activity of K‐feldspar, an important type of mineral dust, in the immersion freezing mode at low cation concentrations (0.2–20 mM) using a droplet‐freezing apparatus. Ammonium cations substantially increased the ice nucleation activity of K‐feldspar, consistent with previous studies. In contrast, primary aminium cations significantly reduced K‐feldspar ice nucleation activity, and secondary and tertiary aminium cations had no significant effect (the effect was less than the uncertainty of our measurements). Our combined results are consistent with the following mechanisms: ammonium cations undergo ion exchange with K‐feldspar, providing exposed N–H groups for hydrogen bonding with ice; primary aminium cations undergo ion exchange with K‐feldspar, exposing a hydrophobic tail that is not effective at nucleating ice; secondary and tertiary aminium cations do not undergo ion exchange with K‐feldspar due to steric effects caused by the multiple hydrophobic groups on the cation. Plain Language Summary: Ice nucleating particles are particles in the atmosphere that can initiate the formation of ice in liquid clouds, impacting cloud properties, precipitation, and climate. Mineral dust is a dominant type of ice nucleating particles in the atmosphere. During atmospheric transport, aminium cations, formed from amine gases which can be abundant in the atmosphere, can coat mineral dust particles altering their ability to nucleate ice. However, the effect of aminium cations on the ice nucleation ability of mineral dust particles has not been studied. We investigated the effects of aminium and ammonium cations on the ice nucleation ability of K‐feldspar, an important type of mineral dust and ice nucleating particles in the atmosphere. Our results show that secondary and tertiary aminium cations have no effect on the ice nucleating ability of K‐feldspar, but primary aminium cations greatly reduce the ice nucleating ability of K‐feldspar. This has possible implications for predicting cloud formation in the atmosphere. We also present a mechanism related to ion exchange that can explain our ice nucleation results. Key Points: Ammonium cations significantly increased the ice nucleation activity of K‐feldsparPrimary aminium cations substantially reduced the ice nucleation activity of K‐feldsparSecondary and tertiary aminium had limited effects on the ice nucleation activity of K‐feldspar due to their inability for ion exchange [ABSTRACT FROM AUTHOR]

The field observations imply that the long‐range transport of carbon dioxide (CO2) emitted by biomass burning (BB) in Southeast Asia might impact the atmospheric CO2 in South China, while the transboundary path and the contributions of long‐range transport on atmospheric CO2 concentrations in South China remain poorly understood. In this study, a regional air quality model system (RAQMS) was developed by incorporating the atmospheric process of CO2 to investigate the impacts of BB in Southeast Asia on tropospheric CO2 concentration over South China in spring during 2009–2018. CO2 emissions from BB in Southeast Asia in spring varied greatly from 2009 to 2018, and high monthly mean emissions were concentrated in the west of Myanmar, the border between Myanmar, Thailand and Laos, the north of Laos, and Cambodia, with the maximum reaching 1.0 g m−2 hr−1. Higher monthly mean concentrations of near surface CO2 and tropospheric CO2 produced by BB were mainly distributed in the source regions of Southeast Asia and South China. The monthly mean tropospheric CO2 concentrations produced by BB in Southeast Asia were higher in March 2010, 2014, and 2015, which were obviously related to the interannual variation of BB emission, and affected by the atmospheric circulation as well. The contribution of BB emission in Southeast Asia to the net change of tropospheric CO2 concentration in South China presented a belt distribution from the southwest to the northeast, with a domain average of 5.7%–38.6% over South China in March 2009–2018. Plain Language Summary: Biomass burning (BB) frequently occurs in spring in Southeast Asia, releasing large amounts of carbon dioxide (CO2) and influencing ecosystem gross primary productivity, which are helpful to warm the Earth. Previous studies mainly pay attention to the impacts of transboundary BB pollutants on air quality in South China, while researches involved with the transboundary CO2 from BB in Southeast Asia and its impacts on atmospheric CO2 are very limited. This study investigates and quantifies the impacts of BB in Southeast Asia on tropospheric CO2 concentration over South China in spring during 2009–2018 through model development and simulation. Several sensitivity experiments are conducted to test the impact of emissions from different inventories on the simulation results and to identify the primary affecting factor for the transboundary CO2 mass from Southeast Asia to China, for example, BB emission amount and meteorological condition. This study provides valuable insights into the transboundary process of the CO2 from BB in Southeast Asia and the contribution of BB emissions and transmissions to tropospheric CO2 concentration over South China, which could be of great significance in carbon accounting and climate change researches. Key Points: Impacts of biomass burning in Southeast Asia on tropospheric CO2 concentration over South China during 2009–2018 are investigatedThe transboundary CO2 from biomass burning significantly increases the atmospheric CO2 concentration in South China in springBiomass burning emission amount is the primary factor affecting the mass of transported CO2 to South China [ABSTRACT FROM AUTHOR]

Atmospheric rivers (ARs) are filaments of enhanced horizontal moisture transport in the atmosphere. Due to their prominent role in the meridional moisture transport and regional weather extremes, ARs have been studied extensively in recent years. Yet, the representations of ARs and their associated precipitation on a global scale remains largely unknown. In this study, we developed an AR detection algorithm specifically for satellite observations using moisture and the geostrophic winds derived from 3D geopotential height field from the combined retrievals of the Atmospheric Infrared Sounder and the Advanced Microwave Sounding Unit on NASA Aqua satellite. This algorithm enables us to develop the first global AR catalog based solely on satellite observations. The satellite‐based AR catalog is then combined with the satellite‐based precipitation (Integrated Muti‐SatellitE Retrievals for GPM) to evaluate the representations of ARs and AR‐induced precipitation in reanalysis products. Our results show that the spreads in AR frequency and AR length distribution are generally small across data sets, while the spread in AR width is relatively larger. Reanalysis products are found to consistently underestimate both mean and extreme AR‐related precipitation. However, all reanalyses tend to precipitate too often under AR conditions, especially over low latitude regions. This finding is consistent with the "drizzling" bias which has plagued generations of climate models. Overall, the findings of this study can help to improve the representations of ARs and associated precipitation in reanalyses and climate models. Plain Language Summary: Atmospheric rivers (ARs) are filaments of enhanced horizontal moisture transport in the atmosphere. These weather systems are responsible for most of the poleward atmospheric moisture transport over midlatitudes and can cause extreme precipitation around the world. For a long time, researchers relied heavily on reanalysis products to study ARs. Albeit incorporating information from observations, reanalyses are produced by numerical models and thus should not be treated as real observations. In this study, for the first time, we developed a near global AR detection algorithm specially for satellite observations. Unlike previous AR detection algorithms designed for satellite observations, which were applicable to mean moisture content and on regional scales, our algorithm utilizes both the moisture field and wind information from satellite observations. Our algorithm can thus better characterize the transport nature of the detected ARs. Using both the developed algorithm and NASA satellite observations, we developed the first satellite‐based near global AR catalog. This satellite‐based AR catalog together with NASA satellite precipitation product was then used to evaluate how well major reanalyses represent ARs and their associated precipitation. We found that reanalyses generally perform well in representing the AR occurrence frequency and length, but show relatively larger uncertainty in representing the AR width. In reanalyses, ARs produce precipitation that is both too weak and too frequent. Our findings can help to improve the representation of ARs and associated precipitation in reanalyses and climate models. As the quality of satellite observations continues to improve, the methodology presented here can be applied to other satellite observations to develop higher resolution or higher frequency AR statistics. Key Points: Developed a novel method to detect atmospheric rivers (ARs) using moisture and wind data from satellite observationsReanalyses and satellite observations show high agreement with each other in AR frequency distributionsUnder AR conditions, reanalyses tend to precipitate too often and too lightly [ABSTRACT FROM AUTHOR]

During the 2019/2020 Australian bushfire season, intense wildfires generated a rising plume with a record concentration of smoke in the lower stratosphere. Motivated by this event, we use the atmospheric wind reanalysis model ERA5 to characterize the three dimensional atmospheric transport in the general region of the plume following a dynamical system approach in the Lagrangian framework. Aided by the Finite Time Lyapunov Exponent tool (FTLE), we identify Lagrangian Coherent Structures (LCS) which simplify the three‐dimensional transport description. Different reduced FTLE formulations are compared to study the impact of the vertical velocity and the vertical shear on the movement of the plume. We then consider in detail some of the uncovered LCS that are directly relevant for the evolution of the plume, as well as other LCS that are less relevant for the plume but have interesting geometries, and we show the presence of 3D lobe dynamics at play. Also, we unveil the qualitatively different dynamical fates of the smoke parcels trajectories depending on the region in which they originated. One feature that had a pronounced influence on the evolution of the smoke plume is a synoptic‐scale anticyclone that was formed near the same time as, and close to the region of, intense wildfires. We analyze this anticyclone in detail, including its formation, the entrainment of the smoke plume, and how it maintained coherence for a long time. Transport paths obtained with the inclusion of the buoyancy effects are compared with those obtained considering only the reanalysis velocity. Plain Language Summary: In the course of the 2019/2020 bushfire season in Australia, there were wildfires that generated a dense plume with a record concentration of smoke in the lower stratosphere. Our study uses Lagrangian techniques to investigate the 3D atmospheric transport of the plume and identify key features of it temporal evolution, including Lagrangian Coherent Structures (LCS). We explore the impact of different factors on the plume movement and uncover fascinating 3D dynamics in the region. Our research also sheds light on the different fates of smoke parcels depending on their origin and the role played by a synoptic‐scale anticyclone in the smoke plume's evolution. We compare transport paths with and without buoyancy effects to gain a better understanding of the plume's behavior. Key Points: The impact of the vertical velocity and the vertical shear is described using different Finite Time Lyapunov Exponent (FTLE) formulationsCoherent regions where smoke parcels have qualitatively different fates are characterized with and without considering buoyancy effectsLagrangian Coherent Structures linked to the anticyclone, which affected the smoke plume's evolution, are analyzed in detail [ABSTRACT FROM AUTHOR]

We assess the Southern Ocean CO2 uptake (1985–2018) using data sets gathered in the REgional Carbon Cycle Assessment and Processes Project Phase 2. The Southern Ocean acted as a sink for CO2 with close agreement between simulation results from global ocean biogeochemistry models (GOBMs, 0.75 ± 0.28 PgC yr−1) and pCO2‐observation‐based products (0.73 ± 0.07 PgC yr−1). This sink is only half that reported by RECCAP1 for the same region and timeframe. The present‐day net uptake is to first order a response to rising atmospheric CO2, driving large amounts of anthropogenic CO2 (Cant) into the ocean, thereby overcompensating the loss of natural CO2 to the atmosphere. An apparent knowledge gap is the increase of the sink since 2000, with pCO2‐products suggesting a growth that is more than twice as strong and uncertain as that of GOBMs (0.26 ± 0.06 and 0.11 ± 0.03 Pg C yr−1 decade−1, respectively). This is despite nearly identical pCO2 trends in GOBMs and pCO2‐products when both products are compared only at the locations where pCO2 was measured. Seasonal analyses revealed agreement in driving processes in winter with uncertainty in the magnitude of outgassing, whereas discrepancies are more fundamental in summer, when GOBMs exhibit difficulties in simulating the effects of the non‐thermal processes of biology and mixing/circulation. Ocean interior accumulation of Cant points to an underestimate of Cant uptake and storage in GOBMs. Future work needs to link surface fluxes and interior ocean transport, build long overdue systematic observation networks and push toward better process understanding of drivers of the carbon cycle. Plain Language Summary: The ocean takes up CO2 from the atmosphere and thus slows climate change. The Southern Ocean has long known to be an important region for ocean CO2 uptake. Here, we bring together all available data sets that estimate the Southern Ocean CO2 uptake, from models that simulate ocean circulation and physical and biological processes that affect the ocean carbon cycle, from surface ocean observation‐based estimates, from atmospheric transport models that ingest atmospheric CO2 observations, and from interior ocean biogeochemical observations. With these data sets, we find good agreement on the mean Southern Ocean CO2 uptake 1985–2018, which is 50% smaller than previous estimates when recalculated for the time period and spatial extent used in the previous estimate. However, the estimates of the temporal change of the Southern Ocean CO2 uptake differ by a factor of two and thus are not in agreement. We further highlight that knowledge gaps exist not only in winter when observations are typically rare, but equally in summer when biology plays a larger role, which is typically represented too simplistically in the dynamic models. Key Points: Ocean models and machine learning estimates agree on the mean Southern Ocean CO2 sink, but the trend since 2000 differs by a factor of twoREgional Carbon Cycle Assessment and Processes Project Phase 2 estimates a 50% smaller Southern Ocean CO2 sink for the same region and timeframe as RECCAP1Large model spread in summer and winter indicates that sustained efforts are required to understand driving processes in all seasons [ABSTRACT FROM AUTHOR]

Arctic warming under increased CO2 peaks in winter, but is influenced by summer forcing via seasonal ocean heat storage. Yet changes in atmospheric heat transport into the Arctic have mainly been investigated in the annual mean or winter, with limited focus on other seasons. We investigate the full seasonal cycle of poleward heat transport modeled with increased CO2 or with individually applied Arctic sea‐ice loss and global sea‐surface warming. We find that a winter reduction in dry heat transport is driven by Arctic sea‐ice loss and warming, while a summer increase in moist heat transport is driven by sub‐Arctic warming and moistening. Intermodel spread in Arctic warming controls spread in seasonal poleward heat transport. These seasonal changes and their intermodel spread are well‐captured by down‐gradient diffusive heat transport. While changes in moist and dry heat transport compensate in the annual‐mean, their opposite seasonality may support non‐compensating effects on Arctic warming. Plain Language Summary: The Arctic is warming much faster than the rest of the planet in response to rising greenhouse gas concentrations. Because Arctic warming peaks in winter, many studies have focused on the wintertime processes amplifying Arctic warming. However, others have found that summer atmospheric heating also contributes to winter warming by melting sea ice and storing heat in the ocean until it is released to the atmosphere in winter. Here we study changes in all seasons for one source of atmospheric heating in the Arctic—atmospheric heat transport from lower latitudes. Using climate model simulations, we find that heat and moisture are transported away from the regions that warm and moisten the most in response to rising greenhouse gas concentrations. The Arctic warms more than lower latitudes in winter, which reduces heat transport to the Arctic in winter. Atmospheric moisture increases most in late summer at lower latitudes, driving increased moisture transport in late summer from lower latitudes to the Arctic. We suggest that changes in heat and moisture transport may impact Arctic warming differently due to their opposite seasonality: by producing a larger change in surface solar absorption, summer changes in moisture transport may outweigh winter changes in heat transport. Key Points: Sea‐ice loss reduces dry heat transport to the Arctic in winter; sub‐Arctic warming increases latent heat transport to the Arctic in summerIntermodel spread in Arctic warming controls intermodel spread in seasonal heat transport changesThe seasonal pattern of poleward heat transport change is well‐captured by down‐gradient diffusion of temperature and moisture anomalies [ABSTRACT FROM AUTHOR]

Arctic warming under increased CO2 peaks in winter, but is influenced by summer forcing via seasonal ocean heat storage. Yet changes in atmospheric heat transport into the Arctic have mainly been investigated in the annual mean or winter, with limited focus on other seasons. We investigate the full seasonal cycle of poleward heat transport modeled with increased CO2 or with individually applied Arctic sea‐ice loss and global sea‐surface warming. We find that a winter reduction in dry heat transport is driven by Arctic sea‐ice loss and warming, while a summer increase in moist heat transport is driven by sub‐Arctic warming and moistening. Intermodel spread in Arctic warming controls spread in seasonal poleward heat transport. These seasonal changes and their intermodel spread are well‐captured by down‐gradient diffusive heat transport. While changes in moist and dry heat transport compensate in the annual‐mean, their opposite seasonality may support non‐compensating effects on Arctic warming. Plain Language Summary: The Arctic is warming much faster than the rest of the planet in response to rising greenhouse gas concentrations. Because Arctic warming peaks in winter, many studies have focused on the wintertime processes amplifying Arctic warming. However, others have found that summer atmospheric heating also contributes to winter warming by melting sea ice and storing heat in the ocean until it is released to the atmosphere in winter. Here we study changes in all seasons for one source of atmospheric heating in the Arctic—atmospheric heat transport from lower latitudes. Using climate model simulations, we find that heat and moisture are transported away from the regions that warm and moisten the most in response to rising greenhouse gas concentrations. The Arctic warms more than lower latitudes in winter, which reduces heat transport to the Arctic in winter. Atmospheric moisture increases most in late summer at lower latitudes, driving increased moisture transport in late summer from lower latitudes to the Arctic. We suggest that changes in heat and moisture transport may impact Arctic warming differently due to their opposite seasonality: by producing a larger change in surface solar absorption, summer changes in moisture transport may outweigh winter changes in heat transport. Key Points: Sea‐ice loss reduces dry heat transport to the Arctic in winter; sub‐Arctic warming increases latent heat transport to the Arctic in summerIntermodel spread in Arctic warming controls intermodel spread in seasonal heat transport changesThe seasonal pattern of poleward heat transport change is well‐captured by down‐gradient diffusion of temperature and moisture anomalies [ABSTRACT FROM AUTHOR]

Estimating isotopic changes of river water on the Tibetan Plateau (TP) remains highly uncertain due to variable water sources related with seasonality of atmospheric circulations and local kinetic fractionation. The in‐depth understanding of such changes is crucial for accurate palaeoaltimetry reconstruction and for river budget evaluation which related with surviving of one‐fifth of the world's population under accelerated warming. Here, we present a comprehensive river water isotopic composition dataset (δ18O, δD and d‐excess, 1852 samples) over the TP to systematically describe spatial distribution and explore possible controlling factors of isotopic data in theses rivers. Results showed that δ18O in river water range from −20.8‰ to −5.2‰ (latitudinally, 0.92‰ per degree), enriching northwardly in the seven exorheic river basins. The d‐excess values range from −19.7‰ to 20.5‰ with the pronounced low values in endorheic rivers basins. We identified that moisture sources and atmospheric transports leave significant signals in isotopic compositions of river water in the Upper Brahmaputra (UB), Upper Mekong (UM) and Upper Yangtze (UYA) basins, and local processes modify the isotopic signals mainly in the Upper Salween (US), Upper Indus (UI), Upper Yellow (UYE) and Endorheic Rivers (ER) basins. The δ18O‐elevation relationships are only established in the UB, UI and UYE with lapse rates of −4.4‰/km, −3.4‰/km and −3.5‰/km, respectively. We suggest that as changes of moisture sources and lapse rates in different basins, it is cautious to apply δ18O‐elevation lapse rates for palaeoaltimetry reconstruction. Our dataset will benefit regional studies of hydrological, biogeochemistry, palaeoaltimetry reconstruction and palaeoclimate. [ABSTRACT FROM AUTHOR]

As air masses move within the troposphere, they transport a multitude of components including gases and particles such as pollen and microorganisms. These movements generate atmospheric highways that connect geographic areas at distant, local, and global scales that particles can ride depending on their aerodynamic properties and their reaction to environmental conditions. In this article we present an approach and an accompanying web application called tropolink for measuring the extent to which distant locations are potentially connected by air‐mass movement. This approach is based on the computation of trajectories of air masses with the HYSPLIT atmospheric transport and dispersion model, and on the computation of connection frequencies, called connectivities, in the purpose of building trajectory‐based geographical networks. It is illustrated for different spatial and temporal scales with three case studies related to plant epidemiology. The web application that we designed allows the user to easily perform intensive computation and mobilize massive archived gridded meteorological data to build weighted directed networks. The analysis of such networks allowed us for example, to describe the potential of invasion of a migratory pest beyond its actual distribution. Our approach could also be used to compute geographical networks generated by air‐mass movement for diverse application domains, for example, to assess long‐term risk of spread from persistent or recurrent sources of pollutants, including wildfire smoke. Plain Language Summary: The movement of air masses within the atmosphere generates air highways connecting distant areas at the local, continental, and global scales. In this article we present an approach and an accompanying web application for measuring how distant locations are potentially connected by air‐mass movement, that is, for representing the geographic networks generated by the above‐mentioned air highways. The approach is illustrated for different spatial and temporal scales with three case studies related to plant epidemiology; one of them concerns the potential invasion routes of a migratory pest. The web application that we developed allows the user to easily perform such studies. It could also be used to compute geographical networks generated by air‐mass movement for other application domains, for example, to assess long‐term risk of spread from sources of pollutants. Key Points: The movement of air masses within the troposphere generate air highway connecting distant areas from local to global scalesOur approach and the accompanying web application tropolink quantifie how distant locations are connected by air‐mass movementOur approach can be used to investigate the spread of small biological particles and organisms [ABSTRACT FROM AUTHOR]

We present a comparison of atmospheric transport models that simulate carbonyl sulfide (COS). This is part II of the ongoing Atmospheric Transport Model Inter‐comparison Project (TransCom–COS). Differently from part I, we focus on seven model intercomparison by transporting two recent COS inversions of NOAA surface data within TM5‐4DVAR and LMDz models. The main goals of TransCom‐COS part II are (a) to compare the COS simulations using the two sets of optimized fluxes with simulations that use a control scenario (part I) and (b) to evaluate the simulated tropospheric COS abundance with aircraft‐based observations from various sources. The output of the seven transport models are grouped in terms of their vertical mixing strength: strong and weak mixing. The results indicate that all transport models capture the meridional distribution of COS at the surface well. Model simulations generally match the aircraft campaigns HIAPER Pole‐To‐Pole Observations (HIPPO) and Atmospheric Tomography Mission (ATom). Comparisons to HIPPO and ATom demonstrate a gap between observed and modeled COS over the Pacific Ocean at 0–40°N, indicating a potential missing source in the free troposphere. The effects of seasonal continental COS uptake by the biosphere, observed on HIPPO and ATom over oceans, is well reproduced by the simulations. We found that the strength of the vertical mixing within the column as represented in the various atmospheric transport models explains much of the model to model differences. We also found that weak‐mixing models transporting the optimized flux derived from the strong‐mixing TM5 model show a too strong seasonal cycle at high latitudes. Plain Language Summary: Carbonyl sulfide (COS) is a significant sulfur‐containing trace gas in the atmosphere, which makes it important for studying climate change. One of the reasons it is worth investigating is because plants take up COS in a similar way as CO2 during photosynthesis. However, the atmospheric sources and sinks of COS are not well understood. To address this knowledge gap, we evaluated the state‐of‐the‐art optimized surface COS fluxes from the inverse models TM5‐4DVAR and LMDz, and then seven atmospheric transport models were used to simulate COS mole fractions by transporting the optimized fluxes under the TransCom‐COS protocol. The results showed good agreement between the simulated COS and COS observations on independent platforms. The study also revealed that COS drawdown due to plant uptake can be observed over Pacific and Atlantic Oceans. However, discrepancies between the model simulations and observations were mainly found in free troposphere, emphasizing the need for further investigation into COS chemistry and model transport differences. These findings provide important reference for further investigation of COS global distribution and budget analysis. Key Points: Simulations in seven models propagating optimized carbonyl sulfide (COS) fluxes derived from two inversions agree with independent observationsSimulated and observed COS drawdowns are captured in boundary layer over the Pacific and Atlantic Oceans due to plant uptake over landsWeak vertical mixing models using fluxes optimized from the fast‐mixing TM5 model overestimate the COS seasonal amplitude at high latitudes [ABSTRACT FROM AUTHOR]

Methane (CH4) is the second most important greenhouse gas. At the global scale, inverse modeling is usually applied to infer CH4 fluxes on the surface. In the inverse model, the chemistry transport model (CTM) is used to link CH4 fluxes to its concentration in the atmosphere. Any uncertainties in the transport and chemical processes modeled by the CTM can lead to biases in the inferred fluxes. Therefore, diagnosing transport processes in the CTM is important for improving the accuracy of inferred fluxes. It is well‐known that the inverse model‐calculated total columns of CH4 contain latitude‐dependent biases when compared to observations. Previous studies revealed that these biases mostly occur in the troposphere. However, we demonstrate in the present study that the model biases in the troposphere can originate in the stratosphere, especially in the lowermost stratosphere, and propagate downward to the troposphere. The propagated biases in the simulations of the atmospheric model TM5‐CAMS are estimated to be about 25 ppb in the mid‐troposphere above the northern high‐latitudes and about 2 ppb over the tropics. At the surface the propagated biases are estimated to be about 20 and 7 ppb in the above two regions, respectively. In addition, the propagated biases display an important zonal asymmetry in the troposphere, especially over the Tibetan‐Plateau, Southeast Asia and tropical South America. It is recommended that some correction functions should be considered in inverse modeling that use surface observations only. Plain Language Summary: Methane (CH4) has important warming effect on Earth's climate and it is important to accurately know its sources. As a tool for inferring CH4 fluxes inverse modeling is used frequently. However, there are still significant uncertainties in the inverse modeling inferred CH4 fluxes. One of the reasons is that atmospheric transport is not correctly represented in the model. Consequently inverse modeled total columns of CH4 present latitudinal biases compared to observations. In this study we investigate stratospheric contribution to the latitudinal biases. The results indicate that stratospheric contribution is not limited in the stratospheric region. Stratospheric model biases can propagate into the troposphere and lead to important biases there. Key Points: Stratospheric biases in the CH4 model can propagate into the troposphere and reach the surfacePropagated model biases in the troposphere present latitudinal and longitudinal dependenceCorrection function should be considered even for inverse model using surface observations only [ABSTRACT FROM AUTHOR]

Liquefaction of natural gas occurs at –162 °C and atmospheric pressure for transporting it over long distances. In the customer's segment, the liquefied natural gas is regasified before distribution. Around 830 kJ kg−1 energy is required for the production of liquefied natural gas and is often saved as cold energy, which can be reused by regasification terminals. Hence, for the past few years, cold energy utilization has been an important topic of research in the energy sector. The different techniques to utilize cold energy for power generation, air fractionation, extraction of natural gas liquids, refrigeration systems, desalination, and dry ice manufacturing are reviewed and discussed. Applying the cold utilization of LNG technique in these systems can help to improve efficiency and decrease operating costs effectively. [ABSTRACT FROM AUTHOR]

Black carbon (BC) particles produced by incomplete combustion of biomass and fossil fuels warm the atmosphere and decrease the reflectivity of snow and ice, hastening their melt. Although the significance of BC in Arctic climate change is widely acknowledged, observations on its deposition and sources are few. We present BC source types in a 300‐year (1700–2005) Svalbard ice core by analysis of particle‐bound organic compounds, radiocarbon, and trace elements. According to the radiocarbon results, 58% of the deposited elemental carbon (EC, thermal‐optical proxy of BC) is of non‐fossil origin throughout the record, while the organic compounds suggest a higher percentage (68%). The contribution of fossil fuels to EC is suggested to have been elevated between 1860 and 1920, particularly based on the organics and trace element data. A second increase in fossil fuel sources seems to have occurred near the end of the record: according to radiocarbon measurements between 1960 and 1990, while the organics and trace element data suggest that the contribution of fossil fuels has increased since the 1970s to the end of the record, along with observed increasing EC deposition. Modeled atmospheric transport between 1948 and 2004 shows that increasing EC deposition observed at the glacier during that period can be associated with increased atmospheric transport from Far East Asia. Further observational BC source data are essential to help target climate change mitigation efforts. The combination of robust radiocarbon with organic compound analyses requiring low sample amounts seems a promising approach for comprehensive Arctic BC source apportionment. Plain Language Summary: Black carbon (BC) is a fine particulate emission component formed in natural and anthropogenic combustion of biomass and fossil fuels. BC effectively warms the atmosphere, and when it is deposited on snow and ice, it hastens their melt. BC strongly amplifies Arctic climate change but information on its deposition variations and sources are still very scarce. We studied sources of BC in a Svalbard (high‐Arctic) ice core covering the years 1700–2005 by analysis of chemical compounds, radiocarbon and trace elements. We found that throughout the ice core, the contribution of biomass combustion to BC was higher (ca. 60%–70%) than that of fossil fuels. The contribution of fossil fuel sources to BC in the ice core was elevated in 1860–1920, and again at the end of the record starting in the 1960s–1970s. Atmospheric transport modeling shows that increasing BC deposition observed at the glacier since the 1970s was associated with airmasses arriving increasingly from Far East Asia. Further observations on Arctic BC sources are essential to inform decision makers on which BC emissions most affect Arctic climate change. Key Points: Non‐fossil sources have dominated (ca. 60%–70%) elemental carbon (EC) deposition in a Svalbard ice core between 1700 and 2005The contribution of fossil fuels to EC was highest between 1860 and 1920 and toward the end of the record starting in the 1960s or 1970sAtmospheric transport modeling indicates that observed increased EC deposition was associated with potential Asian sources in 1948–2004 [ABSTRACT FROM AUTHOR]

In a previous study, we investigated whether reanalysis moist static energy (MSE) transport trends over the 1980 through 2018 period are consistent (a) with each other and (b) with the finding that these transport trends are downgradient, as found in climate models. Regarding point (a), our conclusion was that MSE transport trends were dependent on the reanalysis data set. However, Cox et al. (2023) correctly point out that the reanalysis dependence is reduced dramatically if a barotropic mass flux correction is applied at a monthly mean timescale prior to computing the MSE transport trends. In our reply below, we revisit point (b) after applying this correction. We find that even after the correction, reanalysis MSE transport trends are not downgradient nor poleward in the Northern Hemisphere extratropics. However, reanalysis does show a compensation between dry static and latent energy transport trends, which has been shown in climate models historically. Plain Language Summary: Energy is transported poleward by the atmospheric circulation. As the climate warms, the amount of energy transported poleward is projected to increase. In a previous study, we investigated whether this holds in reanalysis data sets (data sets that obtain global coverage by combining measurements with numerical models). However, as pointed out by Cox et al. (2023), we did not account for the fact that reanalysis products do not respect mass conservation. Correcting for this, MSE transport trends do not exhibit a reanalysis dependence to the degree we previously found. Nevertheless, reanalysis MSE transports are not associated with changes in the surface MSE gradient, as models suggest, nor are these fluxes poleward in the Northern Hemisphere extratropics. An aspect that becomes more consistent between models and reanalysis after correcting the mass budget is an anticorrelation between dry static and latent energy transports trends. Key Points: After mass correction, reanalysis moist static energy (MSE) transport trends are not downgradientAfter mass correction, reanalysis dry static and latent energy transport trends oppose each other over most latitudesThe MSE transport trend is not in a poleward direction north of 30°N [ABSTRACT FROM AUTHOR]

Given the key role that atmospheric heat transport plays in Earth's climate system, efforts to document its changes over the satellite era are valuable. Clark et al. (2022, https://doi.org/10.1029/2022GL098822) calculated trends in atmospheric heat transport among four reanalysis data sets and found substantial disagreements between data sets. However, after accounting for the lack of mass‐conservation in reanalysis data sets, we find much smaller magnitude trends, with much better agreement among reanalyses. This highlights the importance of mass corrections when calculating atmospheric heat transport. Plain Language Summary: Atmospheric heat transport plays an important role in our climate system. Reanalysis data sets provide our best representation of how atmospheric heat transport has changed over the last 40 years. A previous study used four different reanalysis data sets to explore how atmospheric heat transport has changed. They found very large changes that disagreed between data sets. We repeat their calculations, but account for known inaccuracies in the reanalysis data sets and find much better agreement between the data sets. Key Points: It is necessary to account for the lack of mass conservation in reanalysis data sets when calculating atmospheric heat transportClark et al. (2022) found large trends in atmospheric heat transport that differed among reanalysis data sets due to unrealistic mass fluxesTrends in atmospheric heat transport are similar among reanalysis data sets once a mass correction is applied [ABSTRACT FROM AUTHOR]

This study contributes to the communal effort to improve understanding of sea spray generation and transport. For the first time, laboratory‐derived sea spray generation functions (SSGFs) are parameterized in the Meso‐NH mesoscale atmospheric model and are field tested. Formulated from the MATE19 laboratory experiments (Bruch et al., 2021, https://doi.org/10.1007/s10546-021-00636-y) the two SSGFs are driven by the upwind component of the wave‐slope variance 〈Sx2〉 $\langle {S}_{x}^{2}\rangle $ (herein B21A), or both 〈Sx2〉 $\langle {S}_{x}^{2}\rangle $ and the wind friction velocity cubed u∗3 ${u}_{\ast }^{3}$ (herein B21B). In this first attempt to incorporate the SSGFs in Meso‐NH, the simulations are run without a wave model, and the wave‐wind SSGFs are assumed wind‐dependent. Model evaluation is achieved with a new set of sea spray and meteorological measurements acquired over the 0.1–22.75 μm radius range and U10 1–20 m s−1 wind speeds onboard R/V Atalante during the 25 day SUMOS field campaign in the Bay of Biscay. The B21B SSGF offers particularly good sensitivity to a wide range of environmental conditions over the size range, with an average overestimation by a factor 1.5 compared with measurements, well below the deviations reported elsewhere. B21A also performs well for larger droplets at wind speeds above 15 m s−1. Associated with airflow separation and wave breaking, wave‐slope variance allows to represent multiple wave scales and to scale sea spray generation in the laboratory and the field. Using Meso‐NH simulations we find that sea spray may be transported inland and to altitudes well above the marine atmospheric boundary layer. Plain Language Summary: The effects of sea spray on weather and climate remain poorly understood as a result of sparse measurements and large uncertainties in the generation flux. With the aim of improving sea spray transport in atmospheric models, two sea spray generation functions derived from the MATE19 laboratory campaign are parameterized in the Meso‐NH mesoscale atmospheric model. The simulations are run over the Bay of Biscay in February–March 2021, and are compared with super‐micron sea spray concentrations measured during the SUMOS field campaign. Results show that the laboratory‐derived generation functions allow accurate predictions of sea spray concentrations. Furthermore, simulations show that sea spray droplets can be transported far over land, and high into the atmosphere, highlighting their availability to contribute to a wide range of atmospheric processes. Key Points: With comparable wave‐slope variance behavior in laboratory and field conditions we use laboratory‐derived sea spray generation functions in the fieldParameterized with laboratory generation functions and validated using field measurements, Meso‐NH yields accurate sea spray concentrationsBy populating the atmosphere beyond 2.5 km altitude and 100 km inland, sea spray can intervene in a range of weather and cimate processes [ABSTRACT FROM AUTHOR]