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Due to the complexity of the multiple scattering problem for shortwave radiative transfer in Earth's atmosphere, operational physical retrieval algorithms commonly use a plane parallel Radiative Transfer Model (RTM). This so-called One-Dimensional (1-D) assumption allows practical retrieval algorithms to be implemented. In order to understand the impacts of this assumption for low altitude, unresolved clouds observed by OCO-2, the Three-Dimensional (3-D) radiative transfer model SHDOM is used to generate synthetic observations which are then processed by the operational retrieval algorithm based on a 1-D RTM. Simulations are performed over three realistic surface spectral albedos, corresponding to snow, vegetation, and bare soil. The results show that the existing cloud screening algorithm has difficulty identifying sub-Field of View (FOV), unresolved clouds that fill less than half of the FOV. The unresolved clouds introduce a bias in the retrieved CO2 concentration, as quantified by the dry air mole fraction (XCO2). The biases are relatively small (less than 1 ppm) when the albedo at 2.1 µm is high, which is common over bare land surfaces. For cases with low 2.1 µm albedo, such as snow, the bias becomes much larger, up to 5 ppm. These results indicate that the XXCO2 retrieval appears robust to 3-D scattering effects from unresolved low level clouds when the short wave infrared surface albedo is large, but for darker surfaces these clouds can introduce significant biases. [ABSTRACT FROM AUTHOR]

This paper describes an attempt to use data obtained from sodar (sound detection and ranging) for short-term forecasting of PM 10 concentration levels in Krakow. Krakow is one of the most polluted cities in central Europe (CE) in terms of PM 10 concentration. This is due to the high municipal emissions. Thanks to intensive corrective actions taken by the city authorities, these are being effectively eliminated, but the unfavourable topographic location of the city limits natural ventilation. The article describes all these conditions, focusing on presenting the method of short-term correction of air quality for the time needed to take quick corrective actions by the city authorities in the event of anticipated exceedances of the permissible values. Based on several years of measurements of the physical properties of the atmosphere with sodar, the authors of the paper suggest that sodar data could be considered for operational use to generate short-term predictions. The proposed method is based on the use of the spectrum, i.e. the set of amplitudes of signals returning to the sodar receiver from the reflection of a single-frequency sound transmission and its characteristic properties depending on the physical state of the atmosphere. Similar spectra were parameterised with a single numerical value using statistical methods. It was found that, in some cases preceding high concentrations of PM 10 , the spectral parameters had similar values. This made it possible to develop a forecasting method for such concentrations by using data mining to search for conditions in historical data closest to the state of the atmosphere at the time of forecasting. In this part of the study, data from 2017–2018 were used. In the next step, three methods of using the sodar data developed for PM 10 prediction were proposed, comparing them with the method without sodar use. The study results were tested on independent material using data concerning the episodes of high concentrations of pollutants from October 2021 to March 2022 in Krakow. The findings were considered to be encouraging, also taking into account the speed and low cost of preparing the forecast. [ABSTRACT FROM AUTHOR]

The main purpose of this study is to evaluate the near-zero wind velocity measurement performance of two separate 1.5 μm all-fiber coherent Doppler lidars (CDL). The performance characterization is performed through the presentation of the results from two separate atmospheric field campaigns. In one campaign, a recently developed continuous wave (CW) CDL benefiting from an image-reject front-end was deployed. The other campaign utilized a different CW CDL, benefiting from a heterodyne receiver with intermediate frequency (IF) sampling. In both field campaigns the results are compared against a sonic anemometer, as the reference instrument. The measurements clearly show that the image-reject architecture results in more accurate measurements of radial wind velocities close to zero. Close-to-zero velocities are usually associated with the vertical component of the wind and are important to characterize. [ABSTRACT FROM AUTHOR]

This work presents a new iterative method for optimally selecting a vertical retrieval grid based on the location of the information content while accounting for inter-level correlations. Sample atmospheres initially created to parametrise the RTTOV forward model are used to compare the presented iterative vertical selection method with two other common approaches, which are using levels of equal vertical spacing and selecting levels based on the cumulative trace of the averaging kernel matrix (AKM). This new method is shown to outperform compared methods for synthesized profile retrievals with IASI of temperature, H2O, O3, CH4, and CO. However, the benefits of using the more complicated iterative approach compared to the simpler method of referencing the cumulative trace of the AKM are slight and may not justify the added effort. Furthermore, comparing retrievals using a globally optimized static grid vs. an atmosphere specific one shows that a static grid is likely appropriate for retrievals of O3, CH4, and CO. However, developers of temperature and H2O retrieval schemes may at least consider using adaptive or location specific vertical retrieval grids. [ABSTRACT FROM AUTHOR]

Carbon dioxide exchange between the atmosphere and forested subtropical wetlands is largely unknown. Here we report a first step in characterizing this atmospheric-ecosystem carbon (C) exchange, for cypress strands and pine forests in the Greater Everglades of Florida as measured with eddy covariance methods at three locations (Cypress Swamp, Dwarf Cypress and Pine Upland) for one year. Links between water and C cycles are examined at these three sites, and methane emission measured only at the Dwarf Cypress site. Each forested wetland showed net C uptake (retained in the soil and biomass or transported laterally via overland flow) from the atmosphere monthly and annually. Net ecosystem exchange (NEE) of carbon dioxide (CO2) (difference between photosynthesis and respiration, with negative values representing net ecosystem uptake) was greatest at the Cypress Swamp (-1000 gCm-2 year-1), moderate at the Pine Upland (-900 gCm-2 year-1), and least at the Dwarf Cypress (-500 gCm-2 year-1). Methane emission was a negligible part of the C (12 gCm-2 year-1) budget when compared to NEE. However, methane (CH4) production was considerable in terms of global warming potential, as about 20 g CH4 emitted per m² year was equivalent to about 500 g CO2 emitted per m² year. Changes in NEE were clearly a function of seasonality in solar insolation, air temperature and water availability from rainfall. We also note that changes in the satellite-derived enhanced-vegetation index (EVI) served as a useful surrogate for changes in net and gross atmospheric-ecosystem C exchange at these forested wetland sites. [ABSTRACT FROM AUTHOR]

The annual average CO2 difference between baseline data from Mauna Loa and the southern Hemisphere increased by ~ 0.8 µmolmol-1 (0.8 ppm) between 2009 and 2010, a step unprecedented in over 50 years of reliable data. We find no evidence for coinciding, sufficiently large and rapid, source/sink changes. A statistical anomaly is unlikely due to the highly systematic nature of the variation in observations. An explanation for the step, and the subsequent 5 year stability in this north-south difference, involves inter-hemispheric atmospheric exchange variation. The selected data describing this episode provide a critical test for studies that employ atmospheric transport models that interpret global carbon budgets and inform management of anthropogenic emissions. [ABSTRACT FROM AUTHOR]

The atmospheric boundary layer (ABL) exhibit multilayered thermal structure especially in polar atmosphere during extreme winters. These thermal inversions are originated based on the combined forcing of local and large scale synoptic meteorology. At the local scale the thermal inversion layer forms near the surface and plays a central role in controlling the surface radiative cooling; however, depending upon the large scale synoptic meteorological forcing, an upper level thermal inversion can also exist topping the local ABL. In this article a numerical methodology is developed to determine all-thermal inver sion layers present in a given temperature profile and deduce some of their thermodynamic properties. The algorithm extract from the temperature profile the most important temperature variations defining thermal layers. This is accomplished by a linear interpolation function of variable length that minimizes an error function. The algorithm functionality is demonstrated on actual radiosonde profiles to deduce all-present inversion layers with an error fraction set independently. [ABSTRACT FROM AUTHOR]

A convolution based method of spectral nudging of atmospheric fields is developed in the Australian Community Climate and Earth Systems Simulator (ACCESS) version 1.3 which uses the UK Met Office Unified Model version 7.3 as its atmospheric component. The use of convolutions allow flexibility in application to different atmospheric grids. An approximation using one-dimensional convolutions is applied, improving the time taken by the nudging scheme by 10 to 30 times compared with a version using a twodimensional convolution, without measurably degrading its performance. Care needs to be taken in the order of the convolutions and the frequency of nudging to obtain the best outcome. The spectral nudging scheme is benchmarked against a Newtonian relaxation method, nudging winds and air temperature towards ERA-Interim reanalyses. We find that the convolution approach can produce results that are competitive with Newtonian relaxation in both the effectiveness and efficiency of the scheme, while giving the added flexibility of choosing which length scales to nudge. [ABSTRACT FROM AUTHOR]

TEMPERA is a new ground-based radiometer which measures in a frequency range from 51-57 GHz radiation emitted by the atmosphere. The instrument operates thermally stabilized inside a lab. With this instrument it is possible to measure temperature profiles from ground to about 50 km. This is the first ground-based instrument with the capability to retrieve temperature profiles simultaneously for the troposphere and stratosphere. The measurement is done with a filterbank in combination with a digital Fast-Fourier-Transform spectrometer. A hot load and a noise diode are used as stable calibration sources. The optics consist of an off-axis parabolic mirror to collect the sky radiation. Due to the Zeeman effect on the emission lines used, the maximum height for the temperature retrieval is about 50 km. The effect is apparent in the measured spectra. The performance of TEMPERA is validated by comparison with nearby radiosonde and satellite data from the Microwave Limb Sounder on the Aura satellite. In this paper we present the design and measurement method of the instrument followed by a description of the retrieval method, together with a validation of TEMPERA data over its first year, 2012. [ABSTRACT FROM AUTHOR]

The article presents a study which develops a rapid retrieval method for observation of integrated longwave and shortwave top-of-atmosphere irradiances from Meteosat Second Generation (MSG)/SEVIRI (RRUMS). It uses the spatial and temporal resolution of MSG/SEVIRI retrieve the integrated longwave and shortwave radiation. Result shows that the linear combination of the thermal infrared channels can reliably calculate the longwave radiative flux (OLR).

In this paper, we explore different prognostic methods to account for skin sea surface temperature diurnal variations in a coupled ocean–atmosphere regional model of the Mediterranean Sea. Our aim is to characterise the sensitivity of the considered methods with respect to the underlying assumption of how the solar radiation shapes the warm layer of the ocean. All existing prognostic methods truncate solar transmission coefficient at a warm-layer reference depth that is constant in space and time; instead, we implement a new scheme where this latter is estimated from a chlorophyll dataset as the e -folding depth of solar transmission, which thus allows it to vary in space and time depending on seawater's transparency conditions. Comparison against satellite data shows that our new scheme, compared to the one already implemented within the ocean model, improves the spatially averaged diurnal signal, especially during winter, and the seasonally averaged one in spring and autumn, while showing a monthly basin-wide averaged bias smaller than 0.1 K year-round. In April, when most of the drifters' measurements are available, the new scheme mitigates the bias during nighttime, keeping it positive but smaller than 0.12 K during the rest of the monthly averaged day. The new scheme implemented within the ocean model improves the old one by about 0.1 K, particularly during June. All the methods considered here showed differences with respect to objectively analysed profiles confined between 0.5 K during winter and 1 K in summer for both the eastern and the western Mediterranean regions, especially over the uppermost 60 m. The new scheme reduces the RMSE on the top 15 m in the central Mediterranean for summertime months compared to the scheme already implemented within the ocean model. Overall, the surface net total heat flux shows that the use of a skin sea surface temperature (SST) parameterisation brings the budget about 1.5 Wm-2 closer to zero on an annual basis, despite all simulations showing an annual net heat loss from the ocean to the atmosphere. Our "chlorophyll-interactive" method proved to be an effective enhancement of existing methods, its strength relying on an improved physical consistency with the solar extinction implemented in the ocean component. [ABSTRACT FROM AUTHOR]

The upper troposphere/lower stratosphere (UTLS) plays a crucial role in the climate system. Changes in the composition and dynamic structure of this atmospheric region result in particularly large changes in the atmospheric radiation balance. Quantifying the physical and chemical processes that control UTLS composition therefore represents an important task. Currently, there is a lack of UTLS observations with sufficient three-dimensional resolution. The Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) aircraft instrument addresses this observational lack by providing observations of numerous trace constituents as well as temperature and cloud structures with an unprecedented combination of vertical resolution (up to 300 m) and horizontal resolution (up to 20kmx20km). As a result, important scientific questions concerning stratosphere-troposphere-exchange, the occurrence of subvisible cirrus clouds in the lowermost stratosphere (LMS), polar chemistry and gravity wave processes can be addressed, as reviewed in this paper. [ABSTRACT FROM AUTHOR]

Knowledge of vertical air motions in the atmosphere is important for meteorological and climate studies due to its impact on clouds, precipitation and the vertical transport of air masses, heat, momentum, and composition. It is among the most difficult quantities to measure because of its small magnitude. In this study, a descending radiosonde technique has been developed to detect the vertical wind speed (VW) in the atmosphere. The system is composed of a radiosonde and a 0.5-m diameter hard ball made of plastic foam that acts as a parachute. The radiosonde hangs under the hard ball by a string which is then cut when the instrument is elevated into the upper troposphere by a balloon. The VW is derived from the difference between the observed radiosonde descent rate and the calculated radiosonde descent rate in still air based on fluid dynamics. Deduction of the appropriate drag coefficient for the radiosonde is facilitated by the symmetrical shape of the parachute. An intensive radiosonde launch experiment was held in northern China during the summer seasons of 2010 to 2012. This study uses radiosonde data collected during the campaign to retrieve the vertical air velocity within the radiosonde altitude-detecting range. In general, the VW ranges from -1 to 1ms-1. Strong vertical air motion (∼2ms-1) is seen in a few radiosonde measurements. Although considerable uncertainties exist in measuring weak vertical air motions, a case study shows that there is reasonable agreement between retrievals of VW in the lower atmosphere from the radiosonde and a wind profiler radar located at the launch site. [ABSTRACT FROM AUTHOR]

A laser-based analyser for nitrous oxide, carbon monoxide and water vapour was coupled to an equilibrator for continuous high-resolution dissolved gas measurements in the surface ocean. Results for nitrous oxide measurements from laboratory tests and field deployments 5 are presented here. Short-term precision for 10 s-average N2O mole fractions at an acquisition rate of 1 Hz was better than 0.2 nmolmol-1 for standard gases and equilibrator measurements. The same precision was achieved for replicate standard gas analyses within 1 h of each other. The accuracy of the equilibrator measurements was verified by comparison with purge-and-trap GC-MS measurements of 10 N2O concentrations in discrete samples from the Southern Ocean and showed agreement to within the 2% measurement uncertainty of the GC-MS method. Measured atmospheric N2O mole fractions agreed with AGAGE values to within 0.4 %. The equilibrator response time to concentration changes in water was 142 to 203 s, depending on the headspace flow rate. The system was tested at sea during a north-to-south tran15 sect of the Atlantic Ocean. While the subtropical gyres were slightly undersaturated, the equatorial region was a source of nitrous oxide to the atmosphere. The ability to measure at high temporal and spatial resolution revealed sub-mesoscale variability in dissolved N2O concentrations. The magnitude of the observed saturation is in agreement with published data. Mean sea-to-air fluxes in the tropical and subtropical Atlantic 20 ranged between -1.6 and 0.11 µmolm-2 d-1 and confirm that the subtropical Atlantic is not an important source region for N2O to the atmosphere, compared to average global fluxes of 0.6 to 2.4 µmolm-2 d-1.< The system can be easily modified for autonomous operation on voluntary observing ships (VOS). Further work should include an interlaboratory comparison exercise with other methods of dissolved N2O analyses. [ABSTRACT FROM AUTHOR]

Long series of ozone and NO2 total column measurements at the Southern tropics are available from two ground-based SAOZ (Système d'Analyse par Observation Zenithale) UV-visible spectrometers operated within the NDACC (Network for the Detection of Amtospheric Composition Change) deployed in Bauru in S-E Brazil and Re- union Island in the S-W Indian Ocean in 1995 and 1993 respectively. Although at the same latitude, the data show larger columns of both species above the South American continent than above the Indian Ocean. For verifying the reliability of these data before carrying out trend analysis, they have been compared to satellites observations available during the same period. However, since no single satellite was operating from 1995 until present, the comparison requires the building of a composite, called merged satellites series. As systematic differences exist between the individual data sets because of the many differences between instruments, spectral ranges, absorption crosssections, and retrieval procedures used, the building of such a composite requires thorough evaluation and normalisation of each. From comparisons with SAOZ, the merged satellite data set build with EP-TOMS from 1995 to 2004 and OMI-TOMS from 2005 to 2012 are found best for ozone in the Southern tropics. After correction for biases with SAOZ, both are confirming the larger ozone columns reported by SAOZ above South America compared to the Indian Ocean shown to origin from ozone production by lightning NOx (LNOx) over the continent in the summer and the advection from Africa of ozone produced by biomass burning emissions in the winter. For NO2, best matching the SAOZ is a combination of GOME GDP4 1996-2003 and SCIAMACHY 2003-2012 products, after correction for the photochemical diurnal change of the concentration of the species between the SAOZ twilight observations and the time of satellites overpasses. The merged data series built from the data of these two satellites fully confirms the larger NO2 column reported by SAOZ above the South American continent as well as and its seasonality. The 35% larger column above Brazil in the summer is shown to be due to the NOx production in the upper troposphere by the frequent lightning during the thunderstorm season, whereas the winter maximum is shown to come from the larger exchange of NOx rich air with mid-latitudes in the lower stratosphere due to the more equatorial latitude of the subtropical jet above South America compared to the Indian Ocean. [ABSTRACT FROM AUTHOR]

The article focuses on a study which aims at linearizing the effects of spectral stretch and shift in Differential Optical Absorption Spectroscopy (DOAS) analysis. It mentions the use of DOAS in quantifying atmospheric trace gases and describes the methodology of the study in which the spectral shift was linearized in the DOAS. Also discussed are the advantages of linearizing the DOAS equation system.

The article presents a study which analyzed strengthening of precipitation global-scale increase in terms of changes in energy balances and whole atmospheric water. It states that through a combination of water and energy equations, constraints for the surface flux changes were obtained for surface partition between the latent and sensible components. It shows that aerosol forcing may have an effect on decadal-scale predictability of hydrological strength changes.

Fungi are ubiquitous in the atmosphere and may play an important role in atmospheric processes. We investigated the composition and diversity of fungal communities over the Amazon rainforest canopy and compared these communities to fungal communities found in terrestrial environments. We characterized the total fungal community and the metabolically active portion of the community using high-throughout DNA and RNA sequencing and compared these data to predictions generated by a mass-balance model. We found that the total community was primarily comprised of fungi from the phylum Basidiomycota. In contrast, the active community was primarily composed of members of the phylum Ascomycota and included a high relative abundance of lichen fungi, which were not detected in the total community. The relative abundance of Basidiomycota and Ascomycota in the total and active communities was consistent with our model predictions, suggesting that this result was driven by the relative size and number of spores produced by these groups. When compared to other environments, fungal communities in the atmosphere were most similar to communities found in tropical soils and leaf surfaces, suggesting that inputs of fungi to the atmosphere are from local, rather than distant, sources. Our results demonstrate that there are significant diffrences in the composition of the total and active fungal communities in the atmosphere, and that lichen fungi, which have been shown to be efficient ice nucleators, may be abundant members of active atmospheric fungal communities over the forest canopy. [ABSTRACT FROM AUTHOR]

Surface solar radiation (SSR) is an essential factor in the flow of surface energy, enabling accurate capturing of long-term climate change and understanding of the energy balance of Earth's atmosphere system. However, the long-term trend estimation of SSR is subject to significant uncertainties due to the temporal inhomogeneity and the uneven spatial distribution of in situ observations. This paper develops an observational integrated and homogenized global terrestrial (except for Antarctica) station SSR dataset (SSRIH station) by integrating all available SSR observations, including the existing homogenized SSR results. The series is then interpolated in order to obtain a 5 ∘ × 5 ∘ resolution gridded dataset (SSRIH grid). On this basis, we further reconstruct a long-term (1955–2018) global land (except for Antarctica) SSR anomaly dataset with a 5 ∘ × 2.5 ∘ resolution (SSRIH 20CR) by training improved partial convolutional neural network deep-learning methods based on 20th Century Reanalysis version 3 (20CRv3). Based on this, we analysed the global land- (except for Antarctica) and regional-scale SSR trends and spatiotemporal variations. The reconstruction results reflect the distribution of SSR anomalies and have high reliability in filling and reconstructing the missing values. At the global land (except for Antarctica) scale, the decreasing trend of the SSRIH 20CR (- 1.276 ± 0.205 W m -2 per decade) is smaller than the trend of the SSRIH grid (- 1.776 ± 0.230 W m -2 per decade) from 1955 to 1991. The trend of the SSRIH 20CR (0.697 ± 0.359 W m -2 per decade) from 1991 to 2018 is also marginally lower than that of the SSRIH grid (0.851 ± 0.410 W m -2 per decade). At the regional scale, the difference between the SSRIH 20CR and SSRIH grid is more significant in years and areas with insufficient coverage. Asia, Africa, Europe and North America cause the global dimming of the SSRIH 20CR , while Europe and North America drive the global brightening of the SSRIH 20CR. Spatial sampling inadequacies have largely contributed to a bias in the long-term variation of global and regional SSR. This paper's homogenized gridded dataset and the Artificial Intelligence reconstruction gridded dataset (Jiao and Li, 2023) are both available at 10.6084/m9.figshare.21625079.v1. [ABSTRACT FROM AUTHOR]

The organic carbon (OC) pool accumulated in Arctic permafrost (perennially frozen ground) equals the carbon stored in the recent atmosphere. To give an idea of how Yedoma region permafrost could respond under future climatic warming, we conducted a study to quantify the organic matter quality for future decomposition of late Pleistocene (Yedoma) and Holocene (thermokarst) deposits on the Buor Khaya Peninsula, northeast Siberia. The objective of this study was to develop a stratigraphic classified organic matter quality characterization. For this purpose the degree of organic matter decomposition was estimated by using a multiproxy approach. We applied sedimentological (grain-size analyses, bulk density, ice content) and geochemical parameters (total OC, stable carbon isotopes (δ13C), carbon : nitrogen (C/N) ratios) as well as lipid biomarkers (n-alkanes, n-fatty acids, hopanes, triterpenoids, and biomarker proxies/indices: average chain length, carbon preference index (CPI), and higher plant fatty acid index (HPFA)). Our results show that the Yedoma and thermokarst organic matter qualities exhibit no obvious degradation -- depth trend. The C/N, δ13C, and hop-17(21)-ene values and the HPFA index show a better quality of the organic matter stored in thermokarst deposits compared to Yedoma deposits, but the CPI points in the other direction. As the ranges of the proxies mostly overlap, we interpret this as to indicate similar quality for both kind of deposits with perhaps slightly better thermokarst organic matter quality. Supported by principal component analyses, the sediment parameters and quality proxies of Yedoma and thermokarst deposits could not be clearly separated from each other. This lack of clear quality differences revealed that the organic matter vulnerability is heterogeneous, independent from radiocarbon age and depends on different decomposition trajectories and the previous decomposition and preservation history. Elucidating this was one of the major novelties of our multiproxy study. With the addition of biomarker data, it was possible to show that permafrost organic matter degradation likely occurs via a combination of (uncompleted) degradation cycles or a cascade of degradation steps rather than as a linear function of age or sediment facies. We conclude that the amount of organic matter in the studied sediments is high for mineral soils and of good quality and therefore susceptible to future decomposition. The missing depth trends reveal that permafrost acts like a giant freezer, preserving the constant quality of ancient organic matter independently from its age. When unde-composed Yedoma organic matter is mobilized via thermokarst processes, the fate of this carbon depends largely on the environmental conditions; the carbon could be preserved in an undecomposed state till refreezing occurs. If recent input has occurred, thermokarst organic matter could be of a better quality than that found in Yedoma deposits. [ABSTRACT FROM AUTHOR]

Quantifying water vapor and carbon dioxide (CO 2) exchange dynamics between the land and the atmosphere through observations and modeling is necessary in order to reproduce and project near-surface climate in coupled land–atmosphere models. The exchange of water and CO 2 occurs at the leaf surface (leaf level) and in a net manner through exchanges at all the leaf surfaces composing the vegetation canopy and at the soil surface (canopy level). These exchanges depend on the meteorological forcings imposed by the overlying atmosphere (atmospheric boundary layer level). In this paper, we investigate the effect of four canopy environmental variables (photosynthetic active radiation (PAR), water vapor pressure deficit (VPD), air temperature (T), and atmospheric CO 2 concentration (Ca)) on the local individual leaf exchange and canopy exchange of water and CO 2 at hourly timescales. Additionally, we investigate the effect of atmospheric boundary layer (ABL) processes on the local exchange. To that end, we simultaneously investigated the exchanges of water and CO 2 at leaf level and canopy level for an alfalfa field in northern Spain over 1 day in summer 2021. We used comprehensive observations ranging from stomatal conductance to ABL measurements collected during the Land Surface Interactions with the Atmosphere in the Iberian Semi-Arid Environment (LIAISE) experiment. To support the observational analysis, we used a coupled land–atmosphere model (CLASS model) that has representations at all levels considered. To relate how temporal changes of the four environmental variables modify the fluxes of water and CO 2 , we studied tendency equations of the leaf gas exchange. These mathematical expressions quantify the temporal evolution of the leaf gas exchange as a function of the temporal evolution of PAR, VPD, T , and Ca. To investigate the effects of ABL processes on the local exchange, we developed three modeling experiments that impose surface radiative perturbations by a cloud passage (which perturbed PAR, T , and VPD), entrainment of dry air from the free troposphere (which perturbed VPD), and advection of cold air (which perturbed T and VPD). The model results and observations matched the leaf gas exchange (r2 between 0.23 and 0.67) and canopy gas exchange (r2 between 0.90 and 0.95). The tendency equations of the modeled leaf gas exchange during the study day revealed that the temporal dynamics of PAR were the main contributor to the temporal dynamics of the leaf gas exchange, with atmospheric CO 2 temporal dynamics being the least important contributor. From the three modeling experiments with ABL perturbations, the surface radiative changes induced by a cloud perturbed the CO 2 exchange the most, whereas all of them perturbed the water exchange to a similar extent. Second-order effects on the dynamics of the leaf gas exchange were also identified using the tendency equations. For instance, the decrease in the net CO 2 assimilation rate during the cloud passage caused by a decrease in surface radiation was further enhanced due to the decrease in air temperature also associated with the cloud. With this research we showcase that the proposed tendency equations can disentangle the effect of environmental variables on the leaf exchange of water and CO 2 with the atmosphere, as represented in land–surface parameterization schemes. As such, this framework can become a useful tool with which to analyze these schemes in weather and climate models. [ABSTRACT FROM AUTHOR]

A multi-season convection-permitting regional climate simulation of the Maritime Continent (MC) using the Met Office Unified Model (MetUM) with 2.2 km grid spacing is presented and evaluated. The simulations pioneer the use of atmosphere–ocean coupling with the multi-column K profile parametrisation (KPP) mixed-layer ocean model in atmospheric convection-permitting climate simulations. Comparisons are made against a convection-parametrised simulation in which it is nested and which in turn derives boundary conditions from the ERA5 reanalysis. This paper describes the configuration, performance of the mean state and variability in the two simulations compared against observational datasets. The models have both minor sea surface temperature (SST) and wet precipitation biases. The diurnal cycle, representation of equatorial waves, and relationship between SST and precipitation are all improved in the convection-permitting model compared to the convection-parametrised model. The Madden–Julian oscillation (MJO) is present in both models with a faster-than-observed propagation speed. However, it is unclear whether fidelity of the MJO simulation is inherent to the model or whether it predominantly arises from the forcing at the boundaries. [ABSTRACT FROM AUTHOR]

The term "hotspot" refers to the sharp increase in the reflectance occurring when incident (solar) and reflected (viewing) directions almost coincide in the backscatter direction. The accurate simulation of hotspot directional signatures is important for many remote sensing applications. The RossThick–LiSparse–Reciprocal (RTLSR) bidirectional reflectance distribution function (BRDF) model is widely used in radiative transfer simulations, and the hotspot model mostly used is from Maignan–Bréon, but it typically requires large values of numerical quadrature and Fourier expansion terms in order to represent the hotspot accurately for its use coupled with atmospheric radiative transfer modeling (RTM). In this paper, we have developed a modified version based on the Maignan–Bréon's hotspot BRDF model that converges much faster numerically, making it more practical for use in the RTMs that require Fourier expansion of BRDF to simulate the top-of-atmosphere (TOA) hotspot signatures, such as in the RTM models using the Doubling–Adding or discrete ordinate method. Using the vector linearized discrete ordinate radiative transfer model (VLIDORT), we found that reasonable TOA–hotspot accuracy can be obtained with just 23 Fourier terms for clear atmosphere and 63 Fourier terms for atmosphere with aerosol scattering. In order to study the impact of molecular and aerosol scattering on hotspot signatures, we carried out a number of hotspot signature simulations with VLIDORT. We confirmed that (1) atmospheric molecule scattering and the existence of aerosol tend to smooth out the hotspot signature at the TOA and that (2) the hotspot signature at the TOA in the near-infrared is larger than in the visible, and its impact by surface reflectance is more significant. As the hotspot amplitude at the TOA with aerosol scattering included is smaller than that with molecular scattering only, the amplitude of hotspot signature at the surface is likely underestimated in the previous analysis based on the POLDER measurements, where the atmospheric correction was based on a single-scatter Rayleigh-only calculation. This modified model can calculate the amplitude of the hotspot accurately, and, as it agrees very well with the original RossThick model away from the hotspot region, this model can be simply used in conditions with and without hotspots. However, there are some differences in this modified model compared to the original Maignan–Bréon model for the scattering angles close to the hotspot point; thus, it may not be appropriate for those who need an exact representation of the hotspot angular signature. [ABSTRACT FROM AUTHOR]

Soil organic carbon (SOC) is the largest terrestrial carbon pool and sensitive to land use and cover change; its dynamics is critical for carbon cycling in terrestrial ecosystems and the atmosphere. In this study, we combined a modeling approach and field measurements to examine the temporal dynamics of SOC following afforestation of former arable land at six sites under different climatic conditions in the Loess Plateau during 1980-2010. The results showed that the measured mean SOC increased to levels higher than before afforestation when taking the last measurements (i.e., at age 25 to 30 yr), although it decreased in the first few years at the wetter sites. The accumulation rates of SOC were 1.58 to 6.22% yr-1 in the upper 20 cm and 1.62 to 5.15 %yr-1 in the upper 40 cm of soil. The simulations reproduced the basic characteristics of measured SOC dynamics, suggesting that litter input and climatic factors (temperature and precipitation) were the major causes for SOC dynamics and the differences among the sites. They explained 88-96, 48-86 and 57-74% of the variations in annual SOC changes at the soil depths of 0-20, 0-40, and 0-100 cm, respectively. Notably, the simulated SOC decreased during the first few years at all the sites, although the magnitudes of decreases were small at the drier sites. This suggested that the modeling may be advantageous in capturing SOC changes at finer time scale. The discrepancy between the simulation and measurement was a result of uncertainties in model structure, data input, and sampling design. Our findings indicated that afforestation promoted soil carbon sequestration at the study sites, which is favorable for further restoration of the vegetation and environment. Afforestation activities should decrease soil disturbances to reduce carbon release in the early stage. The long-term strategy for carbon fixation capability of the plantations should also consider the climate and site conditions, species adaptability, and successional stage of recovery. [ABSTRACT FROM AUTHOR]

In high-nutrient low-chlorophyll waters of the western Atlantic sector of the Southern Ocean, an intense phytoplankton bloom is observed annually north of South Georgia, most likely due to an enhanced supply of the limiting micronutrient iron. Shallow sediments and atmospheric dust deposition are believed to be the main iron sources. However, their relative importance is still unclear and in the South Georgia region have yet not been ascertained because iron measurements are very few. In this study, we use austral summer dissolved iron (dFe) data around South Georgia (January and February 2008) with a coupled regional hydrodynamic and biogeochemical model to investigate natural iron fertilization around the island. The biogeochemical component of the model includes an iron cycle, where sediments and dust deposition are the sources of iron to the ocean. The model captures the characteristic flow patterns around South Georgia, hence simulating a large phytoplankton bloom to the north, i.e., downstream, of the island. Modelled dFe concentrations agree well with observations (mean difference and root mean square errors of ~ 0.02 nM and ~ 0.81 nM) and form a large plume to the north of the island that extends eastwards for more than 800 km. In agreement with observations, highest dFe concentrations are located along the coast and decrease with distance from the island. Sensitivity tests indicate that most of the iron measured in the main bloom area originates from the coast and the very shallow shelf-sediments (depths < 20 m) while dust deposition plays a minor role, with almost no effects on surface chlorophyll a concentrations. Iron sources such as run-off not represented explicitly in the model, but that likely contribute to the iron plumes observed around South Georgia, are also discussed together with the potential effects their temporal variability may have on the system. [ABSTRACT FROM AUTHOR]

Since the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite first began probing the Earth's atmosphere on 13 June 2006, several research groups dedicated to investigating the atmosphere's optical proper ties have conducted measurement campaigns to validate the CALIPSO data products. Recently, in order to address the lack of CALIPSO validation studies in the Southern Hemisphere, and especially the South American continent, the Lasers Environmental Applications Research Group at Brazil's Nuclear and Energy Research Institute (IPEN) initiated efforts to assess CALIPSO's aerosol lidar ratio estimates using two ground-based remote sensing instruments: a single elastic backscatter lidar system and the AERONET sun photometers installed at five different locations in Brazil. In this study we develop a validation methodology to assess the accuracy of the modeled values of the lidar ratios used by the CALIPSO extinction algorithms. We recognize that the quality of any comparisons between satellite and ground-based measurements de15 pends on the degree to which the instruments are collocated, and that even selecting the best spatial and temporal matches does not provide an unequivocal guarantee that both instruments are measuring the same air mass. The validation methodology presented in this study therefore applies backward and forward air mass trajectories in order to obtain the best possible match between the air masses sampled by the satellite and the ground-based instruments, and thus reduces the uncertainties associated with aerosol air mass variations. Quantitative comparisons of lidar ratio values determined from the combination of AERONET optical depth measurements and CALIOP integrated attenuated backscatter show good agreement with the model values assigned by the CALIOP algorithm. These comparisons yield a mean percentage difference of -2%±26%. Similarly, lidar ratio values retrieved by the elastic backscatter lidar system at IPEN show a mean percentage difference of -2%±15% when compared with CALIOP's lidar ratio. These results confirm the accuracy in the lidar ratio estimates provided by the CALIOP algorithms to within an uncertainty range of no more than 30 %. [ABSTRACT FROM AUTHOR]

The variational formulation of Bayes' theorem allows inferring CO2 sources and sinks from atmospheric concentrations at much higher space-time resolution than the ensemble approach or the analytical one. However, it usually exhibits limited scalable parallelism. This limitation hinders global atmospheric inversions operated on decadal time scales and regional ones with kilometric spatial scales, because of the computational cost of the underlying transport model that has to be run at each iteration of the variational minimization. Here, we introduce a Physical Parallelisation (PP) of variational atmospheric inversions. In the PP, the inversion still manages a single physically and statistically consistent window, but the transport model is run in parallel overlapping sub-segments in order to massively reduce the computation wall clock time of the inversion. For global inversions, a simplification of transport modelling is described to connect the output of all segments. We demonstrate the performance of the approach on a global inversion for CO2 with a 32-yr inversion window (1979-2010) with atmospheric measurements from 81 sites of the NOAA global cooperative air sampling network. In this case, we show that the duration of the inversion is reduced by a sevenfold factor (from months to days) while still processing the three decades consistently and with improved numerical stability. [ABSTRACT FROM AUTHOR]

The article presents a study which evaluates the amplitude of position error for some of the Michelson Interferometer for Passive 20 Atmospheric Sounding (MIPAS) experiments and the effectiveness of information load (IL) analysis in exploiting a one-dimensional (1-D) algorithm of a portion of atmosphere. The study used limb-scanning technique, limb-scanning spectrometer, and 2-D Geo-fit analysis method. Results show that 1-D retrieval leads a sort of effectiveness on the profile of MIPAS.

The article presents a study which compares the mixing rations of N2O5 during NO3 Comp 2007 in the atmosphere simulation chamber SAPHIR in Jülich, Germany. It shows an excellent agreement between measurements using different techniques. It suggests that high aerosol loads can reduce the N2O5 inlet transmission efficiency.

The article presents a study that determines the effect of the structural error of biosphere models when used in assimilating net ecosystem exchange (NEE) measurements to optimize uncertain model parameters within carbon cycle data assimilation 5 systems (CCDASs). It describes the method of the research that observes data from the model-minus-observation mismatch statistics. It notes the result of the study, which confirms the inferred characteristics of the model.

The (net) exchange of reactive nitrogen (Nr) with the atmosphere is an important driver for ecosystem productivity and greenhouse gas exchange. The exchange of airborne Nr includes various trace compounds that usually require different specific measurement techniques, and up to now fast response instruments suitable for eddy covariance measurements are only available for few of these compounds. Here we present eddy covariance flux measurements with a recently introduced converter (TRANC) for the sum of all Nr compounds (σNr). Measurements were performed over a managed grassland field with phases of net emission and net deposition of σNr and alternating dominance of oxidized (NOx) and reduced species (NH3). Spectral analysis of the eddy covariance data exhibited the existence of covariance function peaks at a reasonable time lag related to the sampling tube residence time under stationary conditions. Using ogive analysis, the high-frequency damping was quantified to 19-26 % for a low measurement height of 1.2 m and to about 10 % for 4.8 m measurement height. ΣNr concentrations and fluxes were compared to parallel NO and NO2 measurements by dynamic chambers and NH3 measurements by the aerodynamic gradient technique. The average concentration results indicate that close-to-full conversion of the main compounds NO2 and NH3 was generally obtained by the TRANC system. With an optimised sample inlet also the fluxes of these compounds were recovered fairly including net deposition and net emission phases. The study shows that the TRANC system is suitable for fast response measurements of oxidized and reduced nitrogen compounds and can be used for continuous eddy covariance flux measurements of total reactive nitrogen. [ABSTRACT FROM AUTHOR]

The state of the atmosphere, or of the ocean, cannot be exhaustively observed. Crucial parts might remain out of reach of proper monitoring. Also, defining the exact set of equations driving the atmosphere and ocean is virtually impossible because of their complexity. Hence, the goal of this paper is to obtain predictions of a partially observed dynamical system, without knowing the model equations. In this data-driven context, the article focuses on the Lorenz-63 system, where only the second and third components are observed, and access to the equations is not allowed. To account to those strong constraints, a combination of machine learning and data assimilation techniques is proposed. The key aspects are the following: the introduction of latent variables, a linear approximation of the dynamics, and a database that is updated iteratively, maximising the innovation likelihood. We find that the latent variables inferred by the procedure are related to the successive derivatives of the observed components of the dynamical system. The method is also able to reconstruct accurately the local dynamics of the partially observed system. Overall, the proposed methodology is simple, easy to code, and gives promising results, even in the case of small amounts of observations. [ABSTRACT FROM AUTHOR]

Earth-System and regional models, forecasting climate change and its impacts, simulate atmosphere-ocean gas exchanges using classical yet too simple generalizations relying on wind speed as the sole mediator while neglecting factors as sea-surface agitation, atmospheric stability, current drag with the bottom, rain and surfactants. These were proved fundamental for accurate estimates, particularly in the coastal ocean, where a significant part of the atmosphere-ocean greenhouse gas exchanges occurs. We include several of these factors in a customizable algorithm proposed for the basis of novel couplers of the atmospheric and oceanographic model components. We tested performances with measured and simulated data from the European coastal ocean, having found our algorithm to forecast greenhouse gas exchanges largely different from the forecasted by the generalization currently in use. Our algorithm allows calculus vectorization and parallel processing, improving computational speed roughly 12× in a single cpu core, an essential feature for Earth-System models applications. [ABSTRACT FROM AUTHOR]

We have presented an overview of a mathematical model, BUOYANT, that was originally designed for the evaluation of the dispersion of buoyant plumes originated from major warehouse fires. The model addresses the variations of the cross-plume integrated properties of a buoyant plume in the presence of a vertically varying atmosphere. The model also includes a treatment for a rising buoyant plume interacting with an inversion layer. We have compared the model predictions with the data of two prescribed wild-land fire experiments. For the SCAR-C experiment in Quinault (US) in 1994, the predicted vertical extents of the plume at maximum plume rise were between 500-800 m and 200-700 m, using two alternative meteorological datasets. The corresponding observed injection heights of the aerosol particles measured using an airborne LIDAR (LIght Detection And Ranging) ranged from 250 and 600 m. For the prescribed burning experiment in Hyytiälä (Finland) in 2009, the model predictions were compared with plume elevations and diameters, determined based on particulate matter number concentration measurements on board an aeroplane. The agreement of modelled and measured results was good, provided that one assumes the measured maximum convective heat fluxes as input data for the model. The results demonstrate that in field experiments on wild-land fires, there are substantial uncertainties in estimating both (i) the source terms for the atmospheric dispersion computations, and (ii) the relevant vertical meteorological profiles. The results provide more confidence that cross-plume integrated mathematical models, such as the BUOYANT model, can be used to fairly good accuracy for evaluating the dispersion from major wild-land fires. [ABSTRACT FROM AUTHOR]

Inland waters in general and specifically freshwater reservoirs are recognized as source of CH4 to the atmosphere. Although the diffusion at the air-water interface is the most studied pathway, its spatial and temporal variations are poorly documented. We measured fortnightly CH4 concentrations and physico-chemical parameters at nine stations in a subtropical monomictic reservoir which was flooded in 2008 (Nam Theun 2 Reservoir, Lao PDR). Based on these results, we quantified CH4 storage in the water column and diffusive fluxes from June 2009 to December 2012. We also compared emissions with aerobic methane oxidation calculated from Deshmukh et al. (2015). In this monomictic reservoir, the seasonal variations of CH4 concentration and storage were highly dependant of the thermal stratification. Hypolimnic CH4 concentration and CH4 storage reached their maximum in the warm dry season (WD) when the reservoir was stratified. They decreased during the warm wet (WW) season and reached its minimum after the reservoir overturned in the cool dry season (CD). The sharp decreases of the CH4 storage were concomitant with sporadic extreme diffusive fluxes (up to 200 mmol m-2 d-1). These hot moments of emissions occurred mostly in the inflow region in the WW season and during the overturn in the CD season in the area of the reservoir that has the highest CH4 storage. Although they corresponded to less than 10% of the observations, these CH4 extreme emissions (> 5 mmol m-2 d-1) contributed up to 50% of total annual emissions by diffusion. Based on our fortnightly monitoring, we determined that accurate estimation of the emissions can be determined from measurements made at least at a monthly frequency. During the transition between the WD and WW seasons, a new hotspot of emissions was identified upstream of the water intake where diffusive fluxes peaked at 600 mmol m-2 d-1 in 2010 down to 200 mmol m-2 d-1 in 2012. In the CD season, diffusive fluxes from this area were the lowest observed at the reservoir surface. Emissions from this area contributed 15-25% to total annual emissions although they occur on a surface area representative of less than 1% of the total reservoir surface. We highly recommend measurements of diffusive fluxes around water intakes in order to evaluate if such results can be generalized. [ABSTRACT FROM AUTHOR]

Within the NDACC (Network for the Detection of Atmospheric Composition Change), more than 20 FTIR (Fourier-Transform InfraRed) spectrometers, spread worldwide, provide long-term data records of many atmospheric trace gases.We present a method that uses measured and modelled XCO2 for assessing the consistency of these data records. Our NDACC XCO2 retrieval setup is kept simple so that it can easily be adopted for any NDACC/FTIR-like measurement made since the late 1950s. By a comparison to coincident TCCON (Total Carbon Column Observing Network) measurements, we empirically demonstrate the useful quality of this NDACC XCO2 product(empirically obtained scatter between TCCON and NDACC is about 4‰for daily mean as well as monthly mean comparisons and the bias is 25 ‰). As XCO2 model we developed and used a simple regression model fitted to CarbonTracker results and the Mauna Loa CO2 in-situ records. A comparison to TCCON data suggests an uncertainty of the model for monthly mean data of below 3 ‰. We apply the method to the NDACC/FTIR spectra that are used within the project MUSICA (MUlti-platform remote Sensing of Isotopologues for investigating the Cycle of Atmospheric water) and demonstrate that there is a good consistency for these globally representative set of spectra measured since 1996: the scatter between the modelled and measured XCO2 on a yearly time scale is only 3 ‰. [ABSTRACT FROM AUTHOR]

A globally integrated carbon observation and analysis system is needed to improve the fundamental understanding of the global carbon cycle, to improve our ability to project future changes, and to verify the effectiveness of policies aiming to reduce greenhouse gas emissions and increase carbon sequestration. Building an integrated carbon observation system requires transformational advances from the existing sparse, exploratory framework towards a dense, robust, and sustained system in all components: anthropogenic emissions, the atmosphere, the ocean, and the terrestrial biosphere. The goal of this study is to identify the current state of carbon observations and needs for a global integrated carbon observation system that can be built in the next decade. A key conclusion is the substantial expansion (by several orders of magnitude) of the ground-based observation networks required to reach the high spatial resolution for CO2 and CH4 fluxes, and for carbon stocks for addressing policy relevant objectives, and attributing flux changes to underlying processes in each region. In order to establish flux and stock diagnostics over remote areas such as the southern oceans, tropical forests and the Arctic, in situ observations will have to be complemented with remote-sensing measurements. Remote sensing offers the advantage of dense spatial coverage and frequent revisit. A key challenge is to bring remote sensing measurements to a level of long-term consistency and accuracy so that they can be efficiently combined in models to reduce uncertainties, in synergy with ground-based data. Bringing tight observational constraints on fossil fuel and land use change emissions will be the biggest challenge for deployment of a policy-relevant integrated carbon observation system. This will require in-situ and remotely sensed data at much higher resolution and density than currently achieved for natural fluxes, although over a small land area (cities, industrial sites, power plants), as well as the inclusion of fossil fuel CO2 proxy measurements such as radiocarbon in CO2 and carbon-fuel combustion tracers. Additionally, a policy relevant carbon monitoring system should also provide mechanisms for reconciling regional top-down (atmosphere-based) and bottom-up (surface-based) flux estimates across the range of spatial and temporal scales relevant to mitigation policies. The success of the system will rely on long-term commitments to monitoring, on improved international collaboration to fill gaps in the current observations, on sustained efforts to improve access to the different data streams and make databases inter-operable, and on the calibration of each component of the system to agreed-upon international scales. [ABSTRACT FROM AUTHOR]

Atmospheric ammonia (NH3) dominates global emissions of total reactive nitrogen (Nr), while emissions from agricultural production systems contribute about two thirds of global NH3 emissions; the remaining third emanates from oceans, natural vegetation, humans, wild animals and biomass burning. On land, NH3 emitted from the various sources eventually returns to the biosphere by dry deposition to sink areas, predominantly semi-natural vegetation, and by wet and dry deposition as ammonium (NH4+) to all surfaces. However, the land/atmosphere exchange of gaseous NH3 is in fact bi-directional over unfertilized as well as fertilized ecosystems, with periods and areas of emission and deposition alternating in time (diurnal, seasonal) and space (patchwork landscapes). The exchange is controlled by a range of environmental factors, including meteorology, surface layer turbulence, thermodynamics, air and surface heterogeneous-phase chemistry, canopy geometry, plant development stage, leaf age, organic matter decomposition, soil microbial turnover, and, in agricultural systems, by fertilizer application rate, fertilizer type, soil type, crop type, and agricultural management practices. We review the range of processes controlling NH3 emission and uptake in the different parts of the soil-canopy-atmosphere continuum, with NH3 emission potentials defined at the substrate and leaf levels by different [NH4+] / [H+] ratios (Γ). Surface/atmosphere exchange models for NH3 are necessary to compute the temporal and spatial patterns of emissions and deposition at the soil, plant, field, landscape, regional and global scales, in order to assess the multiple environmental impacts of air-borne and deposited NH3 and NH4+. Models of soil/vegetation/atmosphere NH3 exchange are reviewed from the substrate and leaf scales to the global scale. They range from simple steady-state, "big leaf" canopy resistance models, to dynamic, multi-layer, multi-process, multi-chemical species schemes. Their level of complexity depends on their purpose, the spatial scale at which they are applied, the current level of parameterisation, and the availability of the input data they require. State-of-the-art solutions for determining the emission/sink Γ potentials through the soil/canopy system include coupled, interactive chemical transport models (CTM) and soil/ecosystem modelling at the regional scale. However, it remains a matter for debate to what extent realistic options for future regional and global models should be based on process-based mechanistic versus empirical and regression-type models. Further discussion is needed on the extent and timescale by which new approaches can be used, such as integration with ecosystem models and satellite observations. [ABSTRACT FROM AUTHOR]

The article discusses a study on the strength of biogeochemical cycling process which drives chemical disequilibrium in the Earth's atmosphere. It states that in terms of chemical position earth's atmosphere is far from thermochemical equilibrium state. It mentions that the most significant property to quantify is not the distance from equilibrium but the power needed to drive it.

The eddy-covariance technique is applied worldwide to acquire information about carbon exchange between a variety of ecosystems and atmosphere, but the data acquisition only covers, on average, two-thirds of the whole year due to system failures and data rejection. Therefore, data must be corrected and data gaps must be filled to provide seasonal or annual budgets. The gap-filing strategies, however, are still under discussion within the research community. Presently the major gap-filling methods work quite well for long-time running sites over slow-developing biosphere surfaces such as long-living evergreen forests, but difficulties appear for short-living and fastgrowing croplands. In this study we developed a new Multi-Step Error Filter procedure to gain good-quality data as input for different parameterizations of the light response function of plants for two cropland sites (rice and potatoes), and we could prove that the conventional temperature binning approach is inadequate. The presented timewindow scheme showed best results with a four-day time window for the potato field and an eight-day time window for the rice field. The influence of vapor pressure deficit was tested as well, but in our case it plays a minor role at both the potato and the rice fields with the exception of the early growing stage of the potatoes. Completing our research, we suggest an innovative method by introducing a Leaf Area Index factor to capture the seasonal vegetation development. With this method we are now able to fill the large gaps between observation periods when conventional methods are invalid. [ABSTRACT FROM AUTHOR]

The article discusses the Hadley Centre Global Environment Model version 2 (HadGEM2) family of climate configurations that comprises a range of specific model configurations. It offers a detailed descriptions and evaluations of HadGEM2 family members and its overall performance using a set of model metrics. It notes that HadGEM2 family of configurations includes atmosphere and ocean components with well-resolved stratosphere and earth-system.

Influence of long term trends in the climate parameters (average temperature, wind speed and solar irradiance) on phytoplankton and nutrient in the Baltic Sea was studied with an integrated three-dimensional coupled sea-ice ecological model. Simple ecosystem has been added to the sea-ice model and it has been used to estimate variability of the phytoplankton and nutrient during long term changes of the main atmospheric forces. Several numerical experiments were conducted to test the sensitivity of the model to changes of the main physical parameters such as temperature, wind speed, solar and thermal radiation (in different configurations). Influences of variability of these parameters on phytoplankton and nutrient (total inorganic nitrogen) is presented and discussion on relevance to expected future climate change is provided. [ABSTRACT FROM AUTHOR]

The sensitivity of the biological parameters in a nutrient-phytoplankton-zooplankton-detritus (NPZD) model in the calculation of the air-sea CO2 flux, primary production and detrital export is analysed. The NPZD model is the Hadley Centre Ocean Carbon Cycle model (HadOCC) from the UK Met Office, used in the Hadley Centre Coupled Model 3 (HadCM3) and FAst Met Office and Universities Simulator (FAMOUS) GCMs. Here, HadOCC is coupled to the 1-D General Ocean Turbulence Model (GOTM) and forced with European Centre for Medium-Range Weather Forecasting meteorology to undertake a sensitivity analysis of its twenty biological parameters. Analyses are performed at three sites in the EuroSITES European Ocean Observatory Network: the Central Irminger Sea (60° N 40° W), the Porcupine Abyssal Plain (49° N 16° W) and the European Station for Time series in the Ocean Canary Islands (29° N 15° W) to assess variability in parameter sensitivities at different locations in the North Atlantic Ocean. Reasonable changes to the values of key parameters are shown to have a large effect on the calculation of the air-sea CO2 flux, primary production, and export of biological detritus to the deep ocean. Changes in the values of key parameters have a greater effect in more productive regions than in less productive areas. We perform the analysis using one-at-a-time perturbations and using a statistical emulator, and compare results. The most sensitive parameters are generic to many NPZD ocean ecosystem models. The air-sea CO2 flux is most influenced by variation in the parameters that control phytoplankton growth, detrital sinking and carbonate production by phytoplankton (the rain ratio). Primary production is most sensitive to the parameters that define the shape of the photosythesis-irradiance curve. Export production is most sensitive to the parameters that control the rate of detrital sinking and the remineralisation of detritus. [ABSTRACT FROM AUTHOR]

The article discusses the novel technique for extracting clouds base height which uses a thermal imaging from the ground combined with wind profile data. In here, the method used is being analyzed such as its foundation which is the calculation of the angular velocity of the clouds. It reveals the method's need for an updated wind profile which can obtained either by nearby radiosonde. The article also demonstrates the method's utility for low cumulus, free atmosphere and high cirrus clouds.

A new climatology of stratospheric BrO profiles based on a parameterization using dynamical and chemical indicators has been developed, with the aim to apply it to the retrieval of tropospheric BrO columns from space nadir measurements. The adopted parameterization is based on three years of output data from the 3-D chemistry transport model BASCOE. The impact of the atmospheric dynamics on the stratospheric BrO distribution is treated by means of Bry/ozone correlations built from 3-D-CTM model results, while photochemical effects are taken into account using stratospheric NO2 columns as an indicator of the BrO/Bry ratio. The model simulations have been optimized for bromine chemistry and budget, and validated through comparisons using an extensive data set of ground-based, balloon-borne and satellite limb (SCIAMACHY) stratospheric BrO observations. [ABSTRACT FROM AUTHOR]

The Copernicus Atmosphere Monitoring Service (CAMS) is providing daily analyses and forecasts of the composition of the atmosphere, including the reactive gases such as O3, CO, NO2, HCHO, SO2, aerosol species and greenhouse gases. The global CAMS analysis system (IFS-COMPO) is based on the ECMWF Integrated Forecast System (IFS) for numerical weather prediction (NWP), and assimilates a large number of composition satellite products on top of the meteorological observations ingested in IFS. The CAMS system receives regular upgrades, following the upgrades of IFS. The last upgrade, Cy48R1, operational since 27 June 2023, was major with a large number of code changes, both for COMPO and for NWP. The main COMPO innovations include the introduction of full stratospheric chemistry, a major update of the emissions, of the aerosol model, including the representation of secondary organic aerosol, several updates of the dust life cycle and optics, inorganic chemistry in the troposphere, and the assimilation of VIIRS AOD and TROPOMI CO. The CAMS Cy48R1 upgrade was validated using a large number of independent measurement datasets, including surface in situ, surface remote sensing, routine aircraft and balloon and satellite observations. In this paper we present the validation results for Cy48R1 by comparing with the skill of the previous operational system (Cy47R3), with the independent observations as reference, for the period October 2022 to June 2023 during which daily forecasts from both cycles are available. Major improvements in skill are found for the ozone profile in the lower-middle stratosphere and for stratospheric NO2 due to the inclusion of full stratospheric chemistry. Stratospheric trace gases compare well with ACE-FTS observations between 10–200 hPa, with larger deviations between 1–10 hPa. The impact of the updated emissions is especially visible over East Asia and is beneficial for the trace gases O3, NO2, and SO2. The CO column assimilation is now anchored by IASI instead of MOPITT which is beneficial for most of the CO comparisons, and the assimilation of TROPOMI CO data improves the model CO field in the troposphere. In general the aerosol optical depth has improved globally, but the dust evaluation shows more mixed results. The results of the 47 comparisons are summarised in a score card, which shows that 83 % of the evaluation datasets show a neutral or improved performance of Cy48R1 compared to the previous operational CAMS system, while 17 % indicate a (slight) degradation. This demonstrates the overall success of this upgrade. [ABSTRACT FROM AUTHOR]

In order to improve observations of the atmospheric boundary layer (ABL), the European Meteorological Network, EUMETNET, and the Aerosol, Clouds, and Trace Gases Research Infrastructure, ACTRIS, are currently working on building networks of microwave radiometers (MWRs). Elevation-scanning MWRs are well suited to obtain temperature profiles of the atmosphere, especially within the ABL. Understanding and assessing measurement uncertainties of state-of-the-art scanning MWRs is therefore crucial for accurate temperature profiling. In this paper, we discuss measurement uncertainties due to the instrument setup and originating from external sources, namely (1) horizontal inhomogeneities of the atmosphere, (2) pointing errors or a tilt of the instrument, (3) physical obstacles in the line of sight of the instrument, and (4) radio frequency interference (RFI). Horizontal inhomogeneities from observations at the Jülich Observatory for Cloud Evolution (JOYCE) are shown to have a small impact on retrieved temperature profiles (<|0.22K| in the 25th and 75th percentiles below 3000 m). Typical instrument tilts, that could be caused by uncertainties during the instrument setup, also have a very small impact on temperature profiles and are smaller than 0.1 K below 3000 m for up to 1 ∘ of tilt. Physical obstacles at ambient temperatures and in the line of sight and filling the complete beam of the MWR at the lowest elevation angle of 5.4 ∘ have to be at least 600 m away from the instrument in order to have an impact of less than 0.1 K on obtained temperature profiles. If the obstacle is 5 K warmer than its surroundings then the obstacle should be at least 2700 m away. Finally, we present an approach on how to detect RFI with an MWR with azimuth and elevation-scanning capabilities. In this study, we detect RFIs in a water vapor channel that does not influence temperature retrievals but would be relevant if the MWR were used to detect horizontal humidity inhomogeneities. [ABSTRACT FROM AUTHOR]

Tropical cirrus clouds, i.e., any type of ice cloud with tops above 400 hPa, play a critical role in the climate system and are a major source of uncertainty in our understanding of global warming. Tropical cirrus clouds involve processes spanning a wide range of spatial and temporal scales, from ice microphysics on cloud scales to mesoscale convective organization and planetary wave dynamics. This complexity makes tropical cirrus clouds notoriously difficult to model and has left many important questions stubbornly unanswered. At the same time, their multi-scale nature makes them well-positioned to benefit from the rise of global, high-resolution simulations of Earth's atmosphere and a growing abundance of remotely sensed and in situ observations. Rapid progress on our understanding of tropical cirrus requires coordinated efforts to take advantage of these modern computational and observational abilities. In this opinion paper, we review recent progress in cirrus studies, highlight important unanswered questions, and discuss promising paths forward. Significant progress has been made in understanding the life cycle of convectively generated "anvil" cirrus and the response of their macrophysical properties to large-scale controls. On the other hand, much work remains to be done to fully understand how small-scale anvil processes and the climatological anvil radiative effect will respond to global warming. Thin, in situ formed cirrus clouds are now known to be closely tied to the thermal structure and humidity of the tropical tropopause layer, but microphysical uncertainties prevent a full understanding of this link, as well as the precise amount of water vapor entering the stratosphere. Model representation of ice-nucleating particles, water vapor supersaturation, and ice depositional growth continue to pose great challenges to cirrus modeling. We believe that major advances in the understanding of tropical cirrus can be made through a combination of cross-tool synthesis and cross-scale studies conducted by cross-disciplinary research teams. [ABSTRACT FROM AUTHOR]

To be able to meet global grand challenges (climate change; biodiversity loss; environmental pollution; scarcity of water, food and energy supplies; acidification; deforestation; chemicalization; pandemics), which all are closely interlinked with each other, we need comprehensive open data with proper metadata, along with open science. The large data sets from ground-based in situ observations, ground and satellite remote sensing, and multiscale modeling need to be utilized seamlessly. In this opinion paper, we demonstrate the power of the SMEAR (Station for Measuring Earth surface–Atmosphere Relations) concept via several examples, such as detection of new particle formation and the particles' subsequent growth, quantifying atmosphere–ecosystem feedback loops, and combining comprehensive observations with emergency science and services, as well as studying the effect of COVID-19 restrictions on different air quality and climate variables. The future needs and the potential of comprehensive observations of the environment are summarized. [ABSTRACT FROM AUTHOR]

The ESA Aeolus mission aims to measure wind profiles from space. In preparation for launch we aim to assess the expected bias in retrieved winds from the Mie and Rayleigh channel signals induced by atmospheric heterogeneity. Observation biases are known to be detrimental when gone undetected in Numerical Weather Prediction (NWP). Aeolus processing equipment should therefore be prepared to detect heterogeneous atmospheric scenes and take measures, e.g., reject or reduce the weight of observations when used in NWP. Radiosondes provide the wind vector at about 10m resolution. We present a method to simulate co-located cloud and aerosol optical properties from radiosonde observations. We show that cloud layers can be detected along the radiosonde path from radiosonde measured relative humidity and temperature. A parameterization for aerosol backscatter and extinction along the radiosonde path is presented based on a climatological aerosol backscatter profile and radiosonde relative humidity. The resulting high-resolution database of atmospheric wind and optical properties serves as input for Aeolus wind simulations. It is shown that Aeolus wind error variance grows quadratically with bin size and the wind-shear over the bin. Strong scattering aerosol or cloud layers may cause biases exceeding 1 ms-1 for typical tropospheric conditions and 1 km Mie channel bin size, i.e., substantially larger than the mission bias requirement of 0.4 ms-1. Advanced level-2 processing of Aeolus winds including estimation of atmosphere optical properties is needed to detect regions with large heterogeneity, potentially yielding biased winds. Besides applicable for Aeolus the radiosonde database of co-located high-resolution wind and cloud information can be used for the validation of atmospheric motion wind vectors (AMV) or to correct their height assignment errors. [ABSTRACT FROM AUTHOR]