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The Madden–Julian oscillation (MJO) identified by Madden and Julian in the early 1970s has been well recognized as the most prominent intraseasonal signal in the tropics. Its discovery and its relationship with other weather phenomena such as tropical cyclones (TCs) are among the most significant advancements in modern meteorology with broad and far-reaching impacts. The original study by Madden and Julian used radiosonde data on Canton Island, and their spectral analysis revealed the signal of a 40–50-day oscillation. It has come to our attention that an earlier study by Xie et al. published in a Chinese journal documented an oscillatory signal of a 45-day period using radiosonde data from several stations between 70° and 125°E in the tropics. The 40–50-day signal found by Xie et al. is strikingly evident without any filtering. Xie et al. identified that occurrences of TCs are correlated with the 40–50-day variation of low-level westerlies at these stations. The original figures in Xie et al.'s article were hand drawn. Their results are verified using data from a longer period of 1958–70. The 40–50-day oscillation in the monsoon westerlies and its relationship with the occurrence of TCs are confirmed and further expanded upon. This study serves the purpose of bringing recognition to the community of the identification of a 40–50-day signal published in Chinese in 1963 and the discovery of the correlation between MJO phases and TC genesis three decades earlier than studies on this subject published outside China. [ABSTRACT FROM AUTHOR]

The article celebrates the 30th anniversary of the journal Meteorological Applications and provides a review of its accomplishments and historical context. The journal focuses on meteorological science, including weather and climate, and is aimed at forecasters, applied meteorologists, climate scientists, and users or providers of meteorological and climate services. Over the years, the journal has made changes to its submission and review processes, including moving to a free-format submission process, providing guidance on the use of color in figures, and implementing a double-blind review approach. The journal has seen an increase in the quality of submissions and its impact factor. Looking ahead, the journal plans to launch an Early Career Researcher Board and continue to publish papers on emerging technologies and issues related to climate change, renewable energy, geographic areas of focus, hydrology, economics, and the climate-water-food nexus. The success of the journal is attributed to the dedication and hard work of the editorial team, reviewers, and authors. [Extracted from the article]

Discussion of paper "Numerical generation of inflow turbulence by cell perturbation technique in WRF simulation" by Singh et al. (2020). Inflow turbulence generation, Large-eddy simulation, Cell perturbation method, Atmospheric boundary layers. [Extracted from the article]

Response to discussion of paper "Numerical generation of inflow turbulence by cell perturbation technique in WRF simulation" by Munoz-Esparza et al. Inflow turbulence generation, Cell perturbation, Atmospheric boundary layers. [Extracted from the article]

During autumn 2012 and winter 2013, two Special Observation Periods (SOPs) of the Hydrological cycle in the Mediterranean Experiment (HyMeX) took place. For the preparatory studies and to support the instrument deployment during the field campaign, a dedicated version of the operational convective-scale AROME-France model was developed: the AROME-WMED model. It covers the western Mediterranean basin with a 48 h forecast range. It provided real time analyses and forecasts which were sent daily to the HyMeX operational centre to forecast high precipitation events and to help decision makers on the deployment of observation instruments. This paper presents the main features of this numerical weather prediction system in terms of data assimilation and forecast. Some specific data of the HyMeX SOP were assimilated in real time. The forecast skill of the AROME-WMED is then assessed with objective scores and compared to the operational AROME-France model, for both autumn 2012 (5 September to 6 November 2012) and winter 2013 (1 February to 15 March 2013) SOPs. The overall performance of AROME-WMED is good and similar to those of AROME-France for the 0 to 30 h common forecast range. The 24 to 48 h forecast range is of course less accurate but remains useful for scheduling observation deployment. The characteristics of parameters such as precipitation, temperature or humidity, are illustrated by one heavy precipitation case study that occurred over the south of Spain. [ABSTRACT FROM AUTHOR]

A new one‐dimensional variational (1D‐Var) retrieval method for ionospheric GNSS radio occultation (GNSS‐RO) measurements is described. The forward model implicit in the retrieval calculates the bending angles produced by a one‐dimensional ionospheric electron density profile, modeled with multiple "Vary‐Chap" layers. It is demonstrated that gradient based minimization techniques can be applied to this retrieval problem. The use of ionospheric bending angles is discussed. This approach circumvents the need for Differential Code Bias (DCB) estimates when using the measurements. This new, general retrieval method is applicable to both standard GNSS‐RO retrieval problems, and the truncated geometry of EUMETSAT's Metop Second Generation (Metop‐SG), which will provide GNSS‐RO measurements up to about 600 km above the surface. The climatological a priori information used in the 1D‐Var is effectively a starting point for the 1D‐Var minimization, rather than a strong constraint on the final solution. In this paper the approach has been tested with 143 COSMIC‐1 measurements. We find that the method converges in 135 of the cases, but around 25 of those have high "cost at convergence" values. In the companion paper (Elvidge et al., 2023), a full statistical analysis of the method, using over 10,000 COSMIC‐2 measurements, has been made. Plain Language Summary: This paper presents a new way of estimating the density of electrons in the ionosphere—the part of the Earth's atmosphere in which atoms are ionized by radiation from the Sun. Radio signals sent between GNSS navigational satellites and receivers in a low orbit around the Earth are delayed, and their paths are bent, by the presence of electrons in the ionosphere. Previous attempts to use these observations to estimate the electron density have been based on the delay of the signals. The new approach outlined in this paper uses the bending incurred by the radio waves instead. Such "bending angles" have been used to infer some properties of the lower atmosphere for many years, and are widely available. We demonstrate that by extending these measurements to greater heights, they can provide useful information about the ionosphere as well. Key Points: A new method of deriving ionospheric electron densities, using the difference between bending angles at two different frequenciesIt is based on a 1D variational retrieval, the solution of which is the best fit to the a priori background and the observationsThe forward model assumes the ionosphere to consist of several idealized "Vary‐Chap" electron density layers [ABSTRACT FROM AUTHOR]

Recent decades have witnessed a drastic increase in the fidelity of numerical weather prediction (NWP) modeling. Currently, both research-grade and operational NWP models regularly perform simulations with horizontal grid spacings as fine as 1 km. This migration towards higher resolution potentially improves NWP model solutions by increasing the resolvability of mesoscale processes and reducing dependency on empirical physics parameterizations. However, at the same time, the accuracy of highresolution simulations, particularly in the atmospheric boundary layer (ABL), are also sensitive to orographic forcing which can have significant variability on the same spatial scale as, or smaller than, NWP model grids. Despite this sensitivity, many high resolution atmospheric simulations do not consider uncertainty with respect to selection of static terrain height dataset. In this paper, we use the Weather Research and Forecasting (WRF) model to simulate realistic cases of lower tropospheric flow over and downstream of mountainous islands using both the default global 30 s United States Geographic Survey terrain height dataset (GTOPO30) and the 3 s Shuttle Radar Topography Mission (SRTM) terrain height dataset. Our results demonstrate cases where the differences between GTOPO30-based and SRTM-based model terrain height are significant enough to produce entirely different orographic wake mechanics, such as vortex shedding vs. no vortex shedding. These results are also compared to MODIS visible satellite imagery and highlight the importance of considering uncertain static boundary conditions when running high-resolution mesoscale models. [ABSTRACT FROM AUTHOR]

In this paper we present the current version of the Parallelized Large-Eddy Simulation Model (PALM) whose core has been developed at the Institute of Meteorology and Climatology at Leibniz Universität Hannover (Germany). PALM is a Fortran 95-based code with some Fortran 2003 extensions and has been applied for the simulation of a variety of atmospheric and oceanic boundary layers for more than 15 years. PALM is optimized for use on massively parallel computer architectures and was recently ported to general-purpose graphics processing units. In the present paper we give a detailed description of the current version of the model and its features, such as an embedded Lagrangian cloud model and the possibility to use Cartesian topography. Moreover, we discuss recent model developments and future perspectives for LES applications. [ABSTRACT FROM AUTHOR]

Upper air temperature measurements are critical for understanding weather patterns, boundary-layer processes, climate change, and the validation of space-based observations. However, there have been growing concerns over data discrepancies, the lack of homogeneity, biases, and discontinuities associated with historical climate data records obtained using these technologies. Consequently, this article reviews the progress of utilizing radiosondes and space-based instruments for obtaining upper air temperature records. A systematic review process was performed and focused on papers published between 2000 and 2023. A total of 74,899 publications were retrieved from the Google Scholar, Scopus, and Web of Science databases using a title/abstract/keyword search query. After rigorous screening processes using relevant keywords and the elimination of duplicates, only 599 papers were considered. The papers were subjected to thematic and bibliometric analysis to comprehensively outline the progress, gaps, challenges, and opportunities related to the utilization of radiosonde and space-based instruments for monitoring upper air temperature. The results show that in situ radiosonde measurements and satellite sensors have improved significantly over the past few decades. Recent advances in the bias, uncertainty, and homogeneity correction algorithms (e.g., machine learning approaches) for enhancing upper air temperature observations present great potential in improving numerical weather forecasting, atmospheric boundary studies, satellite data validation, and climate change research. [ABSTRACT FROM AUTHOR]

Predictive high‐fidelity modeling of wind turbines with computational fluid dynamics, wherein turbine geometry is resolved in an atmospheric boundary layer, is important to understanding complex flow accounting for design strategies and operational phenomena such as blade erosion, pitch‐control, stall/vortex‐induced vibrations, and aftermarket add‐ons. The biggest challenge with high‐fidelity modeling is the realization of numerical algorithms that can capture the relevant physics in detail through effective use of high‐performance computing. For modern supercomputers, that means relying on GPUs for acceleration. In this paper, we present ExaWind, a GPU‐enabled open‐source incompressible‐flow hybrid‐computational fluid dynamics framework, comprising the near‐body unstructured grid solver Nalu‐Wind, and the off‐body block‐structured‐grid solver AMR‐Wind, which are coupled using the Topology Independent Overset Grid Assembler. Turbine simulations employ either a pure Reynolds‐averaged Navier–Stokes turbulence model or hybrid turbulence modeling wherein Reynolds‐averaged Navier–Stokes is used for near‐body flow and large eddy simulation is used for off‐body flow. Being two‐way coupled through overset grids, the two solvers enable simulation of flows across a huge range of length scales, for example, 10 orders of magnitude going from O(μm) boundary layers along the blades to O(10 km) across a wind farm. In this paper, we describe the numerical algorithms for geometry‐resolved turbine simulations in atmospheric boundary layers using ExaWind. We present verification studies using canonical flow problems. Validation studies are presented using megawatt‐scale turbines established in literature. Additionally presented are demonstration simulations of a small wind farm under atmospheric inflow with different stability states. [ABSTRACT FROM AUTHOR]

There is a need for further integrated research on developing a set of sustainable development objectives, based on the proposed framework of planetary boundaries indicators. The relevant research questions are divided in this paper into four key categories, related to the underlying processes and selection of key indicators, understanding the impacts of different exposure levels and influence of connections between different types of impacts, a better understanding of different response strategies and the available options to implement changes. Clearly, different categories of scientific disciplines and associated models exist that can contribute to the necessary analysis, noting that the distinctions between them are fuzzy. In the paper, we both indicate how different models relate to the four categories of questions but also how further insights can be obtained by connecting the different disciplines (without necessarily fully integrating them). Research on integration can support planetary boundary quantification in a credible way, linking human drivers and social and biophysical impacts. [ABSTRACT FROM AUTHOR]

The height of the stable boundary layer is a key parameter in atmospheric transmission and diffusion, air quality, emergency response, wind energy, and numerical weather prediction models. Existing methods mainly determine the stable boundary layer height via a threshold or minimum value of the wind speed variance under a low-level jet. Based on multi-meteorological element data from a meteorological gradient observation tower, this paper revealed the limitations of existing methods from the perspective of dynamic and thermal effects. In this paper, it is demonstrated that there were four types of shapes of the wind speed variance profile under the low-level jet and a method for using the shape of the variance profile to retrieve the height of the stable boundary layer was proposed. This method distinguished different types of wind speed variance profiles and solved the problems of the misjudgment and omissions (about 34%) present in existing methods. Our experiment showed that the average absolute error of the proposed method was less than 18 m and the average relative error was less than 9%. The results showed that the proposed inversion method was extended to all kinds of wind field detection equipment for inversion of the stable boundary layer height and has very high universality. [ABSTRACT FROM AUTHOR]

The Global Positioning System (GPS) Radio Occultation (RO) method is a relatively new technique for taking atmospheric measurements for use in both weather and climate studies. As such, this technique needs to be evaluated for all parts of the globe. Here, we present an extensive evaluation of the performance of the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) GPS RO observations of the Southern Ocean boundary layer. The two COSMIC products used here are the "wetPrf" product, which is based on 1-D variational analysis with European Centre for Medium-Range Weather Forecasts (ECMWF), and the "atmPrf" product, which contains the raw measurements from COSMIC. A direct comparison of temporally and spatially co-located COSMIC profiles and high resolution radiosonde profiles from Macquarie Island (54.62° S, 158.85° E) highlights weaknesses in the ability of both COSMIC products to identify the boundary layer structure, as identified by break points in the refractivity profile. In terms of reproducing the temperature and moisture profile in the lowest 2.5 km, the "wetPrf" COSMIC product does not perform as well as an analysis product from the ECMWF. A further statistical analysis is performed on a large number of COSMIC profiles in a region surrounding Macquarie Island. This indicates that, statistically, COSMIC performs well at capturing the heights of main and secondary break points. However the frequency of break points detected is lower than the radiosonde profiles suggest, but this could be simply due to the long horizontal averaging in the COSMIC measurements. There is also a weak seasonal cycle in the boundary layer height, providing some confidence in the ability of COSMIC to detect an important boundary layer variable. [ABSTRACT FROM AUTHOR]

The planetary boundary layer (PBL) is the lowest part of the atmosphere and where its character is directly affected by its contact with the underlying planetary surface. The PBL is responsible for vertical sub-grid-scale fluxes due to eddy transport in the whole atmospheric column. It determines the flux profiles within the well-mixed boundary layer and the more stable layer above. It thus provides an evolutionary model of atmospheric temperature, moisture (including clouds), and horizontal momentum in the entire atmospheric column. For such purposes, several PBL models have been proposed and employed in the weather research and forecasting (WRF) model of which the Yonsei University (YSU) scheme is one. To expedite weather research and prediction, we have put tremendous effort into developing an accelerated implementation of the entire WRF model using Graphics Processing Unit (GPU) massive parallel computing architecture whilst maintaining its accuracy as compared to its CPU-based implementation. This paper presents our efficient GPU-based design on WRF YSU PBL scheme. Using one NVIDIA Tesla K40 GPU, the GPU-based YSU PBL scheme achieves a speedup of 193× with respect to its Central Processing Unit (CPU) counterpart running on one CPU core, whereas the speedup for one CPU socket (4 cores) with respect to one CPU core is only 3.5×. We can even boost the speedup to 360× with respect to one CPU core as two K40 GPUs are applied. [ABSTRACT FROM AUTHOR]

This paper presents results of development of a numerical model of Lagrangian particle transport, as well as results of application of parallel computation methods to improve the efficiency of the software implementation of this model. The model is a software package that allows the transport and deposition of aerosol particles to be calculated taking into account properties of particles and the input data that describe atmospheric conditions and underlying surface geometry. The dynamic core, physical parameterizations, numerical implementation, and algorithm of the model are described. Results of successful verification of the model on analytical solutions are presented. Initially, the model was used for less computationally intensive problems. In this paper, given the need to use the model in more computationally intensive problems, we optimize the sequential software implementation of the model, as well as develop its software implementations that use parallel computing technologies (OpenMP, MPI, and CUDA). The results of testing different implementations of the model show that the optimization of the most computationally complex blocks in its sequential version can reduce the execution time by 27%. At the same time, the use of parallel computing technologies allows us to achieve acceleration by several orders of magnitude. The use of OpenMP in the dynamic block of the model provides almost 4-fold acceleration of this block; the use of MPI, almost 8-fold acceleration; and the use of CUDA, almost 16-fold acceleration (all other conditions being equal). We also give some recommendations on the choice of a parallel computing technology depending on the properties of a computing system. [ABSTRACT FROM AUTHOR]

The Arctic is undergoing rapid changes due to global warming, including the expansion of the marginal ice zone (MIZ), a zone of mixed ice and open water surfaces. To predict the atmospheric interaction with these surfaces, a critical process in climate models, this paper examines a simplified theoretical framework to non-dimensionalize the dynamics of the atmospheric boundary layer (ABL) over a mixed ice-water surface (MIZ–ABL). A heterogeneity Richardson number, Ri h , is proposed to account for the difference in temperature between the ice and water surface in relation to the synoptic pressure gradient forcing. With the wind angle relative to the ice-water interface, α , this framework hypothesizes that these two dimensionless numbers, regardless of individual dimensional variables (surface temperature and geostrophic wind speed) are sufficient to predict the MIZ–ABL dynamics. To test this framework, large-eddy simulations were employed over half-ice and half-water surfaces, with varying surface temperatures and geostrophic wind velocities. While the surface heat fluxes over ice, water, and the aggregate surface seem to be captured reasonably well by α and Ri h , the mean wind and turbulent kinetic energy (TKE) profiles were not, suggesting that not only the difference in stability between the two surface, but also the individual stabilities over each surface influence the dynamics. The wind angle had a significant impact on the results, both in terms of heat fluxes at the surface, turbulent and dispersive fluxes in the MIZ–ABL, and the structure of the secondary circulations. When wind blows perpendicular to the water-ice interface, internal boundary layers are favoured except at the highest Ri h simulated. For cases with wind parallel to the interface, large rolls parallel to the shore emerge. The paper raises at least as many questions as it answers, highlighting the need for further studies of the MIZ–ABL. [ABSTRACT FROM AUTHOR]

This paper introduces the special collection in Geophysical Research Letters and Journal of Geophysical Research: Atmospheres on the exceptional stratospheric polar vortex in 2019/2020. Papers in this collection show that the 2019/2020 stratospheric polar vortex was the strongest, most persistent, and coldest on record in the Arctic. The unprecedented Arctic chemical processing and ozone loss in spring 2020 have been studied using numerous satellite and ground‐based data sets and chemistry‐transport models. Quantitative estimates of chemical loss are broadly consistent among the studies and show profile loss of about the same magnitude as in the Arctic in 2011, but with most loss at lower altitudes; column loss was comparable to or larger than that in 2011. Several papers show evidence of dynamical coupling from the mesosphere down to the surface. Studies of tropospheric influence and impacts link the exceptionally strong vortex to reflection of upward propagating waves and show coupling to tropospheric anomalies, including extreme heat, precipitation, windstorms, and marine cold air outbreaks. Predictability of the exceptional stratospheric polar vortex in 2019/2020 and related predictability of surface conditions are explored. The exceptionally strong stratospheric polar vortex in 2019/2020 highlights the extreme interannual variability in the Arctic winter/spring stratosphere and the far‐reaching consequences of such extremes. Plain Language Summary: The Arctic stratospheric polar vortex—a band of strong winds roughly encircling the pole at about 65°N latitude from about 15 to 50 km above the Earth's surface that forms every winter—was exceptionally strong during the 2019/2020 winter. The strong vortex in the stratosphere was linked to unusual conditions at both higher and lower altitudes. This collection of papers explores the far‐reaching consequences of the exceptionally strong stratospheric polar vortex in 2019/2020, including impacts on Arctic chemical ozone loss and on surface weather conditions. Chemical ozone loss in spring 2020 matched or exceeded the most previously on record (for 2011) and showed some features similar to the larger loss that occurs over the Antarctic every spring. The exceptionally strong stratospheric polar vortex was linked to weather extremes, including record heat, unusual patterns of precipitation, marine cold air outbreaks, and windstorms. Key Points: The stratospheric polar vortex in 2019/2020 was the strongest and longest‐lasting on record as described in this special collectionThis exceptionally strong and cold polar vortex led to unprecedented Arctic ozone loss, approaching that in some Antarctic wintersCirculation anomalies linked to the vortex spanned the mesosphere to the surface with implications for extreme weather and predictability [ABSTRACT FROM AUTHOR]

We have developed a one-dimensional second-order closure numerical model to study the vertical turbulent transport of trace reactive species in the convective (daytime) planetary boundary layer (CBL), which we call the Second-Order Model for Conserved and Reactive Unsteady Scalars (SOMCRUS). The temporal variation of the CBL depth is calculated using a simple mixed-layer model with a constant entrainment coeffcient and zero-order discontinuity at the CBL top. We then calculate time-varying continuous profiles of mean concentrations and vertical turbulent fluxes, variances, and covariances of both conserved and chemically-reactive scalars in a diurnally-varying CBL. The set of reactive species is the O3-NO-NO2 triad. The results for both conserved and reactive species are compared with large-eddy simulations (LES) for the same free-convection case using the same boundary and initial conditions. For the conserved species, we compare three cases with difierent combinations of surface fluxes, and CBL and free-troposphere concentrations. We find good agreement of SOMCRUS with LES for the mean concentrations and fluxes of both conserved and reactive species except near the CBL top, where SOMCRUS predicts a somewhat shallower depth, and has sharp transitions in both the mean and turbulence variables, in contrast to more smeared out variations in the LES due to horizontal averaging. Furthermore, SOMCRUS generally underestimates the variances and species-species covariances. SOMCRUS predicts temperature-species covariances similar to LES near the surface, but much smaller magnitude peak values near the CBL top, and a change in sign of the covariances very near the CBL top, while the LES predicts a change in sign of the covariances in the lower half of the CBL. SOMCRUS is also able to estimate the intensity of segregation (the ratio of the species-species covariance to the product of their means), which can alter the rates of second-order chemical reactions; however, for the case considered here, this efiect is small. The simplicity and extensibility of SOMCRUS means that it can be utilized for a broad range of turbulence mixing scenarios and sets of chemical reactions in the planetary boundary layer; it therefore holds great promise as a tool to incorporate these processes within air quality and climate models. [ABSTRACT FROM AUTHOR]

The sporadic E‐layer (Es) exhibits unique opportunity for exploring the coupling from lower to upper atmosphere. It was found that the East Asia is with the highest intensity and occurrence probability of Es. By using the long‐term data of 21 ionosonde stations in China and Japan over the past 60 yrs, this paper explores the probable control on the Es layer from the lower layers. It is found that the intensity of the Es layer is strongly correlated with the surface atmospheric temperature, terrain, and land‐sea boundary. The correlation coefficient of the intensity of Es with surface temperature is as high as 0.8204, while that with the terrain and land‐sea boundary is up to 0.6668. Based on the coupling between the lower and upper atmosphere, this paper reveals the probable controls from lower layers on the intensity of the Es in East Asia. Plain Language Summary: As an occasional ionized layer of the ionosphere, the sporadic E‐layer (Es) exhibits unique opportunity for exploring the coupling from lower to upper atmosphere. Despite extensive research on both behavior and mechanism of the Es, none have adequately explained the strong inhomogeneous of its global morphology. It is found in fact that the East Asia is with the highest intensity and occurrence probability of Es. By using the long‐term data of 21 ionosondes in China and Japan over the past 60 yrs, this letter explores the formation mechanism of the strongest Es regions in the world. It is found that the intensity of the Es layer is strongly correlated with the surface atmospheric temperature, terrain, and land‐sea boundary. The correlation coefficient between the intensity of Es and surface temperature is highest, while that with the terrain and land‐sea boundary is also high. By analyzing the data as long as six decades, this letter reveals the probable controls from lower layers on the intensity of the Es in East Asia. Key Points: By analyzing the six‐decade data of 21 ionosondes in East Asia, it reveals probable controls on the strongest Es layer from lower layersFor the first time, it is found that the intensity of Es layer is highly correlated with the surface atmospheric temperatureAn interesting coupling from lower to upper atmosphere may be found by taking advantage of observations longer than half of a century [ABSTRACT FROM AUTHOR]

Interannual fluctuations in average summertime temperatures across the western United States are captured by a leading empirical orthogonal function that explains over 50% of the total observed variance. In this paper, we explain the origins of this pattern of interannual temperature variability by examining soil moisture–temperature coupling that acts across seasons in observations and climate models. We find that a characteristic pattern of coupled temperature–soil moisture climate variability accounts for 34% of the total observed variance in summertime temperature across the region. This pattern is reproduced in state-of-the-art global climate models, where experiments that eliminate soil moisture variability reduce summertime average temperature variance by a factor of 3 on average. We use an idealized model of the coupled atmospheric boundary layer and underlying land surface to demonstrate that feedbacks between soil moisture, boundary layer relative humidity, and precipitation can explain the observed relations between springtime soil moisture and summertime temperature. Our results suggest that antecedent soil moisture conditions and subsequent land–atmosphere interactions play an important role in interannual summertime temperature variability in the western United States; soil moisture variations cause distal temperature anomalies and impart predictability at time scales longer than one season. Our results indicate that 40% of the observed warming trend across the western United States since 1981 has been driven by wintertime precipitation trends in the U.S. southwest. Significance Statement: Year-to-year fluctuations in summertime temperatures have a large impact on drought, wildfire, and extreme heat across the Western United States. We find strong evidence that soil moisture deficits in the preceding spring may be the primary driver of higher-than-average summer temperatures in this region. Our results suggest that memory in the water cycle may lead to greater predictability in the climate system from season to season and that trends in southwest precipitation have exerted a considerable influence on observed warming over the past 40 years. [ABSTRACT FROM AUTHOR]

In 2022, Houston, TX became a nexus for field campaigns aiming to further our understanding of the feedbacks between convective clouds, aerosols and atmospheric boundary layer (ABL) properties. Houston's proximity to the Gulf of Mexico and Galveston Bay motivated the collection of spatially distributed observations to disentangle coastal and urban processes. This paper presents a value-added ABL dataset derived from observations collected by eight research teams over 46 days between 2 June - 18 September 2022. The dataset spans 14 sites distributed within a ~80-km radius around Houston. Measurements from three types of instruments are analyzed to objectively provide estimates of nine ABL parameters, both thermodynamic (potential temperature, and relative humidity profiles and thermodynamic ABL depth) and dynamic (horizontal wind speed and direction, mean vertical velocity, updraft and downdraft speed profiles, and dynamical ABL depth). Contextual information about cloud occurrence is also provided. The dataset is prepared on a uniform time-height grid of 1 h and 30 m resolution to facilitate its use as a benchmark for forthcoming numerical simulations and the fundamental study of atmospheric processes. [ABSTRACT FROM AUTHOR]

Exoplanet atmospheres are expected to vary significantly in thickness and chemical composition, leading to a continuum of differences in surface pressure and atmospheric density. This variability is exemplified within our Solar System, where the four rocky planets exhibit surface pressures ranging from 1 nPa on Mercury to 9.2 MPa on Venus. The direct effects and potential challenges of atmospheric pressure and density on life have rarely been discussed. For instance, atmospheric density directly affects the possibility of active flight in organisms, a critical factor since without it, dispersing across extensive and inhospitable terrains becomes a major limitation for the expansion of complex life. In this paper, we propose the existence of a critical atmospheric density threshold below which active flight is unfeasible, significantly impacting biosphere development. To qualitatively assess this threshold and differentiate it from energy availability constraints, we analyze the limits of active flight on Earth, using the common fruit fly, Drosophila melanogaster, as a model organism. We subjected Drosophila melanogaster to various atmospheric density scenarios and reviewed previous data on flight limitations. Our observations show that flies in an N2-enriched environment recover active flying abilities more efficiently than those in a helium-enriched environment, highlighting behavioral differences attributable to atmospheric density vs. oxygen deprivation. [ABSTRACT FROM AUTHOR]

This paper provides a comprehensive review of recent theoretical investigations concerning magnetohydrodynamic (MHD) waves in partially ionized solar plasma. First, we examine the properties of linear MHD waves in a uniform partially ionized plasma and discuss the relevant effects arising from partial ionization. Subsequently, we delve into MHD wave studies in the more intricate settings of the lower solar atmosphere and solar prominences. These investigations involve topics such as MHD waves in magnetic flux tubes, wave excitation, linear and nonlinear mode coupling and wave heating. We outline new challenges that future research should tackle. This article is part of the theme issue 'Partially ionized plasma of the solar atmosphere: recent advances and future pathways'. [ABSTRACT FROM AUTHOR]

To catalyze transformative advancements in High-energy Physics in the Atmosphere (HEPA), a comprehensive understanding of particle fluxes, electric fields, and lightning occurrences across atmospheric layers is imperative. This paper elucidates the instrumentation and capabilities of the Aragats Space-Environmental Center (ASEC), which encompasses measurement tools for various cosmic ray species, near-surface electric fields, and lightning events integrated across high-mountain research station at slopes of Mt. Aragats and the highest mountains of Eastern Europe and Germany. Through these measurements, we aim to elucidate models of particle acceleration mechanisms and the charge distribution within the lower atmosphere. We introduce an Advanced Data Extraction Infrastructure (ADEI) integrated with sophisticated statistical analysis tools to facilitate rapid access to this wealth of data. Despite the significance of these atmospheric processes, the intricate interplay between thundercloud electrification, lightning activity, wideband radio emissions, and particle fluxes remains poorly understood. A particularly compelling avenue of inquiry lies in exploring the relationship between high-energy atmospheric phenomena, intracloud electric fields, and lightning initiation. Furthermore, investigations into accelerated structures within geospace plasmas hold promise for shedding light on particle acceleration processes, potentially extending to higher energies within analogous structures in cosmic plasmas. This paper also examines practical methodologies for extracting meaningful physical insights from temporal datasets, such as correlating surges in particle flux intensity with variations in near-surface electric field strength and precipitation patterns. Additionally, we explore the utility of wideband field and interferometer antenna signals in this context, offering valuable avenues for further research and analysis. Through these endeavors, we aim to deepen our understanding of high-energy atmospheric processes and their broader implications for terrestrial and cosmic phenomena. [ABSTRACT FROM AUTHOR]

Earth system science indicates the existence of planetary boundaries. Several of these ecological limits have been transgressed, raising serious human rights concerns. Concurrently, persistent poverty and significant economic disparities continue to challenge societies and human rights law and scholarship. How to reform economies to respect planetary boundaries and at the same time address deprivation and socio-economic inequalities is the subject of a rich 'degrowth' literature. Surprisingly, this literature received minimal attention from human rights scholarship. Building upon Raworth's influential concept of Doughnut Economics, this paper aims to bridge this gap by investigating whether human rights can encompass ecological limits (outer circle of the doughnut) and how these limits relate to social priorities embodied in human rights law (inner circle of the doughnut). To do so, the paper is structured along two sub-sections. The first section examines the relevance of core planetary boundaries, particularly biosphere integrity and climate change, within the context of human rights law. In the second section, the paper addresses the relationship between the inner and outer circle of doughnut economics from a human rights perspective. Drawing on critical literature, the article problematizes the 'growth paradigm' in human rights practice but also offers alternative readings. In this final part of the article, the author demonstrates how central doctrines of ESC rights, such as progressive realization and non-retrogression, could be interpreted in a way agnostic of economic growth. [ABSTRACT FROM AUTHOR]

The need to develop and provide integrated observation systems to better understand and manage global and regional environmental change is one of the major challenges facing Earth system science today. In 2008, the German Helmholtz Association took up this challenge and launched the German research infrastructure TERrestrial ENvironmental Observatories (TERENO). The aim of TERENO is the establishment and maintenance of a network of observatories as a basis for an interdisciplinary and long‐term research program to investigate the effects of global environmental change on terrestrial ecosystems and their socio‐economic consequences. State‐of‐the‐art methods from the field of environmental monitoring, geophysics, remote sensing, and modeling are used to record and analyze states and fluxes in different environmental disciplines from groundwater through the vadose zone, surface water, and biosphere, up to the lower atmosphere. Over the past 15 years we have collectively gained experience in operating a long‐term observing network, thereby overcoming unexpected operational and institutional challenges, exceeding expectations, and facilitating new research. Today, the TERENO network is a key pillar for environmental modeling and forecasting in Germany, an information hub for practitioners and policy stakeholders in agriculture, forestry, and water management at regional to national levels, a nucleus for international collaboration, academic training and scientific outreach, an important anchor for large‐scale experiments, and a trigger for methodological innovation and technological progress. This article describes TERENO's key services and functions, presents the main lessons learned from this 15‐year effort, and emphasizes the need to continue long‐term integrated environmental monitoring programmes in the future. Plain Language Summary: This paper discusses the importance of creating comprehensive environmental observation systems to better understand and address global and regional environmental changes. In 2008, a German research infrastructure named Terrestrial Environmental Observatories (TERENO) was established to build and maintain a network of observatories. The goal is to conduct interdisciplinary, long‐term research on the impacts of global environmental changes on terrestrial ecosystems and their socio‐economic effects. The TERENO network employs advanced methods from environmental monitoring, geophysics, remote sensing, and modeling to study various environmental aspects. Over the past 15 years, four observatories have been part of this network, contributing to valuable experience in overcoming challenges and exceeding expectations. Today, TERENO is a crucial component for environmental modeling and forecasting in Germany, serving as an information hub for practitioners and policymakers. It also fosters international collaboration, supports large‐scale experiments, and drives methodological and technological advancements. The article highlights key lessons learned from this 15‐year effort and emphasizes the importance of continuing such integrated environmental monitoring programs in the future. Key Points: Integrated observatories ensure a holistic Earth Systems perspective, offering data for current and future ecological challengesThe scientific and societal value of observatories is invaluable, but their design, construction and operation require considerable effortFor assured long‐term data collection, research infrastructure must have flexible design for adapting to changing research needs [ABSTRACT FROM AUTHOR]

Flux footprint models are often used for interpretation of flux tower measurements, to estimate position and size of surface source areas, and the relative contribution of passive scalar sources to measured fluxes. Accurate knowledge of footprints is of crucial importance for any upscaling exercises from single site flux measurements to ecosystem or regional scale. Hence, footprint models are ultimately also of considerable importance for improved greenhouse gas budgeting. With increasing numbers of flux towers within large monitoring networks such as FLUXNET, ICOS, NEON, or AMERIFLUX, and with increasing temporal range of observations from such towers (order of decades) and availability of airborne flux measurements, there has been an increasing demand for reliable footprint estimation. Even though several sophisticated footprint models have been developed in recent years, most are still not suitable for application to long time series, due to their high computational demands. Existing fast footprint models, on the other hand, are based on Surface Layer theory and hence are of restricted validity for real case applications. To remedy such shortcomings, we present the two-dimensional Flux Footprint Parameterisation, FFP, based on a novel scaling approach for the crosswind distribution of the flux footprint and on an improved version of the footprint parameterisation of Kljun et al. (2004b). Compared to the latter, FFP now provides not only the extent, but also the width and shape of footprint estimates, and explicit consideration of the effects of the surface roughness length. The footprint parameterisation has been developed and evaluated using simulations of the backward Lagrangian stochastic particle dispersion model LPDM-B (Kljun et al., 2002). Like LPDM-B, the parameterisation is valid for a broad range of boundary layer conditions and measurement heights over the entire planetary boundary layer. Thus it can provide footprint estimates for a wide range of real case applications. The new footprint parameterisation requires inputs that can be easily determined from, for example, flux tower measurements or airborne flux data. FFP can be applied to data of long-term monitoring programmes as well as be used for quick footprint estimates in the field, or for designing new sites. [ABSTRACT FROM AUTHOR]

We examine the influence of the grid aspect ratio of horizontal to vertical grid spacing on turbulence in the planetary boundary layer (PBL) in a large-eddy simulation (LES). In order to distinguish them as much as possible from other artificial effects caused by numerical schemes, we used a fully compressible meteorological LES model with a fully explicit scheme of temporal integration. The influences are investigated with a series of sensitivity tests with parameter sweeps of spatial resolution and grid aspect ratio. We confirmed that the mixing length of the eddy viscosity and diffusion due to sub-grid scale turbulence plays an essential role in reproducing the theoretical -5/3 slope of the energy spectrum. If we define the filter length in LES modeling based on consideration of the numerical scheme, and introduce a corrective factor for the grid aspect ratio into the mixing length, the theoretical slope of the energy spectrum can be obtained; otherwise, spurious energy piling appears at high wavenumbers. We also found that the grid aspect ratio has influence on the turbulent statistics, especially the skewness of the vertical velocity near the top of the PBL, which becomes spuriously large with large aspect ratio, even if a reasonable spectrum is obtained. [ABSTRACT FROM AUTHOR]

Active remote sensing of marine boundary-layer clouds is challenging as drizzle drops often dominate the observed radar reflectivity. We present a new method to simultaneously retrieve cloud and drizzle vertical profiles in drizzling boundary-layer cloud using surface-based observations of radar reflectivity, lidar attenuated backscatter, and zenith radiances. Specifically, the vertical structure of droplet size and water content of both cloud and drizzle is characterised throughout the cloud. An ensemble optimal estimation approach provides full error statistics given the uncertainty in the observations. To evaluate the new method, we first perform retrievals using synthetic measurements from large-eddy simulation snapshots of cumulus under stratocumulus, where cloud water path is retrieved with an error of 31 gm-2. The method also performs well in non-drizzling clouds where no assumption of the cloud profile is required. We then apply the method to observations of marine stratocumulus obtained during the Atmospheric Radiation Measurement MAGIC deployment in the northeast Pacific. Here, retrieved cloud water path agrees well with independent 3-channel microwave radiometer retrievals, with a root mean square difference of 10-20 gm-2. [ABSTRACT FROM AUTHOR]

An innovative calibration method for the wind speed measurement using a boom mounted Rosemount model 858 AJ air velocity probe is introduced. The method is demonstrated for a sensor system installed on a medium size research aircraft which is used for measurements in the atmospheric boundary layer. The method encounters a series of coordinated flight manoeuvres to directly estimate the aerodynamic influences on the probe and to calculate the measurement uncertainties. The introduction of a differential Global Positioning System (DGPS) combined with a high accuracy Inertial Reference System (IRS) has brought major advances to airborne measurement techniques. The exact determination of geometrical height allows the use of the pressure signal as an independent parameter. Furthermore, the exact height information and the stepwise calibration process lead to maximum accuracy. The results show a measurement uncertainty for the aerodynamic influence of the dynamic and static pressures of 0.1hPa. The applied para-metrisation does not require any height dependencies or time shifts. After extensive flight tests a correction for the flow angles (attack and sideslip angles) was found, which is necessary for a successful wind calculation. A new method is demonstrated to correct for the aerodynamic influence on the sideslip angle. For the 3-D wind vector (with 100Hz resolution) a novel error propagation scheme is tested, which determines the measurement uncertainties to be 0.3ms-1 for the horizontal and 0.2ms-1 for the vertical wind components. [ABSTRACT FROM AUTHOR]

Planetary boundary layer (PBL) CO2 mole fraction data are needed by transport models and carbon budget models as both input and reference for validation. The height of in situ CO2 mole fraction measurements is usually different from that of the model levels where the data are needed; data from short towers, in particular, are dificult to utilize in atmospheric models that do not simulate the surface layer well. Tall tower CO2 mole fraction measurements observed at heights ranging from to 115ma.g.l. at a rural site in Hungary and regular airborne vertical mole fraction profile measurements (136 vertical profiles) above the tower allowed us to estimate how well a tower of a given height could estimate the CO2 mole fraction above the tower in the PBL. The statistical evaluation of the height-dependent bias between the real PBL CO2 mole fraction profile (measured by the aircraft) and the measurement at a given elevation above the ground was performed separately for the summer and winter half years to take into account the different dynamics of the lower troposphere and the different surface CO2 flux in the dif15 ferent seasons. The paper presents: (1) how accurately the vertical distribution of CO2 in the PBL can be estimated from the measurements on the top of a tower of height H, (2) how tall a tower would be needed for the satisfaction of different requirements on the accuracy of the estimation of the CO2 vertical distribution, (3) how accurate a CO2 vertical distribution estimation can be expected from the existing towers; and (4) how much improvement can be achieved in the accuracy of the estimation of CO2 vertical distribution applying the virtual tall tower concept. [ABSTRACT FROM AUTHOR]

Simulating surface wind over complex terrain is a challenge in regional climate modelling. Therefore, this study aims at identifying a setup of the WRF model that minimizes systematic errors of surface winds in hindcast simulations. Major factors of the model configuration are tested to find a suitable setup: the horizontal resolution, the PBL parameterization scheme and the way WRF is nested to the driving dataset. Hence, a number of sensitivity simulations at a spatial resolution of 2 km are carried out and compared to observations. Given the importance of wind storms, the analysis is based on case studies of 24 historical wind storms that caused great economic damage in Switzerland. Each of these events is downscaled using eight different model setups, but sharing the same driving dataset. The results show that the unresolved topography leads to a general overestimation of wind speed in WRF. However, this bias can be substantially reduced by using a PBL scheme that explicitly considers the effects of non-resolved topography, which also improves the spatial structure of wind speed over Switzerland. The wind direction, although generally well reproduced, is not very sensitive to the PBL scheme. Further sensitivity tests include four types of nesting methods: nesting only at the boundaries of the outermost domain, analysis and spectral nudging, and the so-called re-forecast method, where the simulation is frequently restarted. These simulations show that restricting the freedom of the model to develop large-scale disturbances slightly increases the temporal agreement with the observations, at the same time that it further reduces the overestimation of wind speed, especially for maximum wind peaks. The model skill is also evaluated in the outermost domains, where the resolution is coarser. The results demonstrate the important role of horizontal resolution, where the step from 6 to 2 km significantly improves model performance. In summary, the combination of a grid size of 2 km, the non-local PBL scheme modified to explicitly account for non-resolved orography, as well as analysis or spectral nudging, is a superior combination when dynamical downscaling is aimed at reproducing real wind fields. [ABSTRACT FROM AUTHOR]

Three months of Doppler lidar wind measurements were obtained during the Arctic Cloud Summer Experiment on the icebreaker Oden during the summer of 2014. Such ship-borne measurements require active stabilisation to remove the effects of ship motion. We demonstrate that the combination of a commercial Doppler lidar with a custom-made motion-stabilisation platform enables the retrieval of wind profiles in the Arctic boundary layer during both cruising and ice-breaking with statistical uncertainties comparable to land-based measurements. This holds particularly within the planetary boundary layer even though the overall aerosol load was very low. Motion stabilisation was successful for high wind speeds in open water and the resulting wave conditions. It allows for the retrieval of winds with a random error below 0.2ms-1, comparable to the measurement error of standard radiosondes. The combination of a motion-stabilised platform with a low-maintenance autonomous Doppler lidar has the potential to enable continuous long-term high-resolution ship-based wind profile measurements over the oceans. [ABSTRACT FROM AUTHOR]

In network real‐time kinematic positioning of multi‐reference station, the spatial and temporal distribution of tropospheric delay is affected by both horizontal and elevation. The traditional modeling strategy of regional troposphere takes more consideration of the horizontal factor, and the incomplete consideration of the elevation factor will lead to the problem of reduced modeling accuracy, especially in the face of the scene with large regional height deviation. Based on the traditional linear interpolation method (LIM), a simple and effective height‐deviation compensation‐based linear interpolation method (HCLIM) for regional tropospheric is proposed. The modeling accuracy of troposphere and the positioning accuracy of user RTK in large height deviation region are significantly improved. The method was verified based on six experimental subnets with large height deviations from a provincial continuously operating GNSS reference stations network in central China. The results showed that: For GPS satellite modeling, compared with the traditional LIM method, the average modeling accuracy improvement rate of HCLIM method is (84.5%, 75.5%, 59.3%, 26.7%) in the elevation angle range of (10–30°/30–40°/40–50°/50–90°). For BDS satellite, the average modeling accuracy improvement rate of HCLIM method in the above four elevation angles is (83.3%, 70%, 50%, 23.5%). For the positioning performance of user RTK, The horizontal positioning accuracy and RTK fixing rate were similar under the two methods, while HCLIM method showed only slight improvement. However, in the U direction, LIM method showed obvious systematic bias, while HCLIM method showed consistent positioning accuracy, which was improved to 82.8% compared with LIM method. Plain Language Summary: In GNSS relative positioning, the positioning performance of user largely depends on the extent to which atmospheric deviations (ionospheric delay or tropospheric delay) are eliminated or weakened. Compared with the ionosphere, the temporal and spatial characteristics of troposphere are significantly different. It is part of the lower atmosphere, extends from the Earth's surface to an altitude of about 20 km, and contains most of the atmospheric water vapor. The delay of satellite signals through the troposphere is affected by both horizontal and elevation. The traditional tropospheric regional modeling strategy only uses plane coordinates for interpolation, ignoring the influence of elevation factors or the consideration of height‐deviation is not perfect. When the height difference between the reference station and the rover station is large, the modeling accuracy will obviously be reduced. The large modeling residual may bring systematic deviation to the user coordinates, especially the elevation direction component. In this paper, we propose a regional tropospheric linear interpolation method (HCLIM) considering height deviation compensation. This method is simple and effective, The modeling accuracy of troposphere and the positioning accuracy of user RTK in large height difference region are significantly improved. Key Points: A simple and effective height‐deviation compensation‐based linear interpolation method (HCLIM) for regional tropospheric is proposedThe HCLIM method greatly improves the tropospheric modeling accuracy of each elevation angle range in the large height difference site areaThe HCLIM method significantly improves the systematic bias in elevation direction of user RTK positioning due to modeling residuals [ABSTRACT FROM AUTHOR]

The study of supersonic jet flows from a nozzle is significant in practical applications in jet engine and rocket technology. This paper studies supersonic reacting jet flows from a threedimensional (3D) divergent conical nozzle. We assume that the flow is governed by 3D steady Zeldovich-von Neumann-Döring combustion equations with cylindrical symmetry and that the state of the flow is given at the inlet of the nozzle. When the nozzle is surrounded by a vacuum, we obtain a global continuous and piecewise smooth supersonic reacting jet flow expanding into the vacuum from the nozzle. When the nozzle is surrounded by a static atmosphere with a lower pressure than the pressure of the flow at the exit of the nozzle, we obtain a local continuous and piecewise smooth supersonic reacting jet flow expanding into the atmosphere from the nozzle. Moreover, we also give an explanation for the formation of intercepting shocks in supersonic jets expanding into a lower pressure environment, which is stated in section 148 in the famous book Supersonic Flow and Shock Waves and is verified by physical experiments. The flow patterns constructed in the paper may be used as background solutions for more general supersonic jet flow problems. The result in the paper is also suitable for nonreacting supersonic jet flows. [ABSTRACT FROM AUTHOR]

Rotation in hurricane flows can significantly impact the dynamics and structure of the turbulent boundary layer. Despite this unique feature of hurricane boundary layers, the current planetary boundary layer (PBL) schemes in weather models are neither specifically designed nor comprehensively tested for intensifying hurricane flows. The objective of this paper is to bridge this knowledge gap by characterizing the role of vertical diffusion depth and magnitude in simulated hurricane intensity, size, and track. To this end, five major hurricane cases undergoing an intensification period are simulated using two widely used local and non-local PBL schemes in Weather Research and Forecasting (WRF) model. In total, eighty WRF simulations are conducted by varying the grid resolution, PBL scheme, eddy diffusivity depth and magnitude, and PBL height. By decreasing the existing vertical diffusion depth and magnitude, on average, ~ 38 and ~ 24% improvements in hurricane intensity forecasts were obtained compared to the default models. Hence, the results indicate that the current PBL schemes in WRF are overly diffusive for simulating major hurricanes since they do not account for turbulence suppression effects in rotating hurricane flows. The paper yields new insights into the role of vertical diffusion in simulated hurricane dynamics and provides some guidance to enhance the PBL schemes of NWPs for improved hurricane forecasts. [ABSTRACT FROM AUTHOR]

One of the key issues in architectural design and regional planning is to create a safe and comfortable outdoor building environment, which calls for more studies. Wind tunnel experiments and computational fluid dynamic (CFD) simulations are the primary methods for the current studies. The airflow and boundary conditions are controllable for the wind tunnel experiment, and the data is reliable. In most wind tunnel platforms, spires and roughness elements are applied to create the gradient wind of the atmospheric boundary layer, leading to the oversized, high construction cost, and complex operation. In this paper, in order to explore a simple method for measuring and studying the outdoor building wind environment using wind tunnels, a compact wind tunnel platform adopting grids with unequal spacing was designed and tested, based on the theoretical model of the atmospheric boundary layer. A comparison between the test results and the theoretical values indicated that this new wind tunnel platform could achieve a gradient wind field and is accessible in applying low-speed wind tunnels to the measurement and research of the building wind environment. The application case in a high-rise building of the central business district (CBD) region in Beijing, was presented in this paper. Compared with another analytical method, the CFD simulation, the compact wind tunnel revealed its applicability that could be used for predicting and evaluating the outdoor wind environment around the building. This compact wind tunnel is more flexible and convenient than the traditional ones, with a smaller size, easier construction and operation, and lower costs. Therefore, we suggest more applications of this compact wind tunnel platform in future experimental studies of outdoor wind environments. [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]

The characteristics of South American biomass burning (BB) aerosols transported over northern and central Argentina were investigated from July to December 2019. This period was chosen due to the high aerosol optical depth values found in the region and because simultaneously intensive biomass burning took place over the Amazon. More specifically, a combination of remote sensing observations with simulated air parcel back trajectories was used to link the optical and physical properties of three BB aerosol events that affected Pilar Observatory (PO, Argentina, 31°41′S, 63°53′W, 338 m above sea level), with low-level atmospheric circulation patterns and with types of vegetation burned in specific fire regions. The lidar observations at the PO site were used for the first time to characterize the vertical extent and structure of BB aerosol plumes as well as their connection with the planetary boundary layer, and dust particles. Based mainly on the air-parcel trajectories, a local transport regime and a long transport regime were identified. We found that in all the BB aerosol event cases studied in this paper, light-absorbing fine-mode aerosols were detected, resulting mainly from a mixture of aging smoke and dust particles. In the remote transport regime, the main sources of the BB aerosols reaching PO were associated with Amazonian rainforest wildfires. These aerosols were transported into northern and central Argentina within a strong low-level jet circulation. During the local transport regime, the BB aerosols were linked with closer fires related to tropical forests, cropland, grassland, and scrub/shrubland vegetation types in southeastern South America. Moreover, aerosols carried by the remote transport regime were associated with a high aerosol loading and enhanced aging and relatively smaller particle sizes, while aerosols associated with the local transport pattern were consistently less affected by the aging effect and showed larger sizes and low aerosol loading. [ABSTRACT FROM AUTHOR]

The current paper evaluates the weather research and forecasting (WRF) model sensitivity to five different combinations of cumulus, microphysics, radiation, and planetary boundary layer (PBL) schemes over Loess Plateau for the period 2015, in terms of 2 m temperature and precipitation. The WRF configuration consists of a 10 km resolution domain nested in a coarser domain driven by European Center for Medium-Range Weather Forecasts Reanalysis (ERA-Interim) data. The model simulated 2 m temperature and precipitation have been evaluated at daily and monthly scales with gridded observational dataset. The analysis shows that all experiments reproduce well the daily 2 m temperature, with overestimation particularly in the low-temperature range. Precipitation is less well simulated, with underestimation in all range, especially for intense rainfall. Comparing with ERA-Interim, WRF shows no clear benefit in simulating daily 2 m temperature while prominent improvement in simulating daily precipitation. WRF simulations capture the annual cycle of monthly 2 m temperature and precipitation with a warm bias and wet bias for most experiments in summer. Some reasonable configurations are identified. The "best" configuration depends on the criteria. [ABSTRACT FROM AUTHOR]

Since the tropopause was first identified, the quality and resolution of weather balloons has dramatically improved. NOAA Earth System Research Laboratories (ESRL) have provided high resolution and very high quality ozonesondes from eight locations: Fiji; American Samoa; Greenland; Antarctica; and several locations in USA (Hawai'i, Colorado, California and Alabama). These locations collectively cover polar regions, mid‐latitudes and tropics. Using this publicly archived data set, we studied the variability of the tropopause for all eight locations for one complete year (2016). Along with the standard estimates of the tropopause provided by NOAA ESRL, we developed four alternative tropopause definitions each based on changes in one of the following: (a) molar density; (b) temperature lapse rates; (c) water vapor content; (d) ozone content. These old and new tropopause definitions appear to hold over all eight locations—for all seasons and from the tropics to the poles. The cohesiveness between all five of these independent tropopause definitions is remarkable, although the NOAA ESRL estimates sometimes identify higher tropopause onsets than the other estimates. Therefore, each tropopause definition could potentially be used as proxies for other tropopause definitions. However, it also confirms that the troposphere/tropopause transition is a multi‐faceted physical and chemical phenomenon associated with more than just temperature changes. Finally, these high‐resolution results suggest that the original term "tropopause" might be a misnomer since they suggest increases in temperature lapse rate variability, rather than the "pausing" implied by lower resolution data or by lapse rates that are averaged over large distances. Plain Language Summary: In the lower atmosphere ("the troposphere"), the temperature decreases with height. This is why it is colder on mountaintops. Since 1902, it has been known that higher up in the atmosphere, in the region near where commercial airplanes fly, temperatures remain relatively constant with height. This region is called "the tropopause." In 1957, the World Meteorological Organization (WMO) defined the start of the tropopause in terms of a set of rules, that were complex, but designed to be applicable for all latitudes and seasons. However, these rules are often hard to implement and can give ambiguous results. So, other definitions have been developed for specific regions, such as the tropics, that are more straightforward and easier to interpret. In this paper, we have developed four new tropopause definitions that can be used with modern high resolution "ozonesondes" (weather balloons that also measure ozone). These four independent definitions describe different aspects of the atmosphere but each give very similar estimates of the tropopause. This reveals that the tropopause involves many different but synchronous changes in the atmosphere. It also shows that the name "tropopause" is confusing because it is a part of the atmosphere involving lots of changes instead of "pausing." Key Points: Four new tropopause definitions have been developed for use with high‐resolution ozonesondes that work for all latitudes and seasonsAll these definitions yield almost identical tropopause estimates yet are derived from independent physical or chemical metricsSurprisingly, the "tropopause" marks a region with increased lapse rate variability over short altitudes as opposed to long‐term averages [ABSTRACT FROM AUTHOR]

The growth in the number and size of wind energy projects in the last decade has revealed structural limitations in the current approach adopted by the wind industry to assess potential wind farm sites. These limitations are the result of neglecting the mutual interaction of large wind farms and the thermally stratified atmospheric boundary layer. While currently available analytical models are sufficiently accurate to conduct site assessments for isolated rotors or small wind turbine clusters, the wind farm's interaction with the atmosphere cannot be neglected for large-size arrays. Specifically, the wind farm displaces the boundary layer vertically, triggering atmospheric gravity waves that induce large-scale horizontal pressure gradients. These perturbations in pressure alter the velocity field at the turbine locations, ultimately affecting global wind farm power production. The implication of such dynamics can also produce an extended blockage region upstream of the first turbines and a favorable pressure gradient inside the wind farm. In this paper, we present the multi-scale coupled (MSC) model, a novel approach that allows the simultaneous prediction of micro-scale effects occurring at the wind turbine scale, such as individual wake interactions and rotor induction, and meso-scale phenomena occurring at the wind farm scale and larger, such as atmospheric gravity waves. This is achieved by evaluating wake models on a spatially heterogeneous background velocity field obtained from a reduced-order meso-scale model. Verification of the MSC model is performed against two large-eddy simulations (LESs) with similar average inflow velocity profiles and a different capping inversion strength, so that two distinct interfacial gravity wave regimes are produced, i.e. subcritical and supercritical. Interfacial waves can produce high blockage in the first case, as they are allowed to propagate upstream. On the other hand, in the supercritical regime their propagation speed is less than their advection velocity, and upstream blockage is only operated by internal waves. The MSC model not only proves to successfully capture both local induction and global blockage effects in the two analyzed regimes, but also captures the interaction between the wind farm and gravity waves, underestimating wind farm power by about only 2% compared with the LES results. Conversely, wake models alone cannot distinguish between differences in thermal stratification, even if combined with a local induction model. Specifically, they are affected by a first-row overprediction bias that leads to an overestimation of the wind farm power by 13% to 20% for the modeled regimes. [ABSTRACT FROM AUTHOR]

The main goal of the TRacking Aerosol Convection interactions ExpeRiment (TRACER) project was to further understand the role that regional circulations and aerosol loading play in the convective cloud life cycle across the greater Houston, Texas, area. To accomplish this goal, the United States Department of Energy and research partners collaborated to deploy atmospheric observing systems across the region. Cloud and precipitation radars, radiosondes, and air quality sensors captured atmospheric and cloud characteristics. A dense lower-atmospheric dataset was developed using ground-based remote sensors, a tethersonde, and uncrewed aerial systems (UASs). TRACER-UAS is a subproject that deployed two UAS platforms to gather high-resolution observations in the lower atmosphere between 1 June and 30 September 2022. The University of Oklahoma CopterSonde and the University of Colorado Boulder RAAVEN (Robust Autonomous Aerial Vehicle – Endurant Nimble) were flown at two coastal locations between the Gulf of Mexico and Houston. The University of Colorado Boulder RAAVEN gathered measurements of atmospheric thermodynamic state, winds and turbulence, and aerosol size distribution. Meanwhile, the University of Oklahoma CopterSonde system operated on a regular basis to resolve the vertical structure of the thermodynamic and kinematic state. Together, a complementary dataset of over 200 flight hours across 61 d was generated, and data from each platform proved to be in strong agreement. In this paper, the platforms and respective data collection and processing are described. The dataset described herein provides information on boundary layer evolution, the sea breeze circulation, conditions prior to and nearby deep convection, and the vertical structure and evolution of aerosols. The quality-controlled TRACER-UAS observations from the CopterSonde and RAAVEN can be found at 10.5439/1969004 (Lappin, 2023) and 10.5439/1985470 (de Boer, 2023), respectively. [ABSTRACT FROM AUTHOR]

This paper introduces a machine-learning-driven approach for automated Nocturnal Low-Level Jet (NLLJ) identification using observations of wind profiles from a Radar Wind Profiler (RWP). The work discussed here is an effort to lay the groundwork for a systematic study of the Mid-Atlantic NLLJ's formation mechanisms and their influence on nocturnal and diurnal air quality in major urban regions by establishing a general framework of NLLJ features and characteristics with an identification algorithm. Leveraging a comprehensive wind profile dataset maintained by the Maryland Department of Environment's RWP network, our methodology employs supervised machine learning techniques to isolate the features of the south-westerly NLLJ. This methodology was developed to illuminate spatiotemporal patterns and nuanced characteristics of NLLJ events, unveiling their significant role in shaping the planetary boundary layer. This paper discusses the construction of this methodology, its performance against known NLLJs in the current literature, intended usage, and a preliminary statistical analysis. First light results from this analysis have identified a total of 90 south-westerly NLLJs from May–September of 2017–2021 as captured by the RWP stationed in Beltsville, MD (39.05°, -76.87°, 135 m ASL). A composite of these 90 jets is presented to better illustrate many of the bulk parameters, such as core height, duration, and maximum wind speed, associated with the onset and decay of the Mid-Atlantic NLLJ. We hope our study equips researchers and policymakers with further means to monitor, predict, and address these nocturnal dynamics phenomena that frequently influence boundary layer composition and air quality in the U.S. Mid-Atlantic and Northeastern regions. [ABSTRACT FROM AUTHOR]

Two ∼2‐week Ultra‐Fast Kelvin Wave (UFKW) events centered on days 158(203) during 2021 are investigated using winds, temperatures, plasma drifts and electron densities (Ne) measured by the Ionospheric CONnections (ICON) mission. Eastward‐propagating longitudinal wave‐1 (s = −1) structures with periods 2.5–4.0d, thought to mainly reflect Ultra‐Fast Kelvin waves (UFKWs), reveal ±45 ms−1 zonal winds (U) at 100 km for both events. Height‐latitude structures of the 3.0(3.5)d‐period UFKWs are obtained for the first time for both temperature (T, 94–120 km) and U (94–280 km) between 12°S and 39°N latitude. Maximum values of 36(29) ms−1 for U and 12(15)K for T occur at 102(106) km altitude and within ±3° latitude. The U‐T peak height displacement remains unexplained. Vertical wavelengths are in the range 36–43 km for both U and T during both events. Concurrent with the E‐region dynamo winds, topside (580 km) F‐region field‐aligned (±20–40 ms−1), meridional (±5–10 ms−1) and vertical (±5–10 ms−1) drift and Ne (±20–40%) 2.5–4.0d s = −1 variations are also measured. These key elements of atmosphere‐ionosphere (A‐I) coupling, contemporaneously measured for the first time, are relevant to testing the internal consistency of A‐I models. The mean wind propagation environment of the UFKWs is also quantified, showing no appreciable effects on the UFKW structures, consistent with modeling and theory. Plain Language Summary: Atmospheric Ultra‐Fast Kelvin waves (UFKWs) are eastward‐ and vertically propagating oscillations with periods less than 1 week that are centered on the equator and confined to low latitudes. They are part of a whole spectrum of waves forced by the spatial‐temporal variability of the heat of condensation ("latent heating") that is released when rising moist air forms rain droplets, mainly in the tropics. At high altitudes UFKW reach large amplitudes due to the decrease in ambient density with height. Their growth is curtailed by the viscosity of the atmosphere near 102 km altitude where they reach maximum amplitudes. Here they interact with ionized particles (the ionosphere) and generate electric fields that ultimately drive ionospheric variability at higher altitudes (>200 km), thus presenting an element of "space weather" to navigation and communications systems. In this paper, UFKWs measured in connection with the ICON mission are used to reveal, for the first time, the height and latitudinal structures of temperatures and winds associated with UFKWs in this dissipative regime, and their corresponding effect on the ionosphere. These results can thus serve to assess the internal consistency of models that seek to simulate atmosphere‐ionosphere coupling and related space weather effects induced by the wave spectrum excited in the lower atmosphere. Key Points: First coincident UFKW winds and temperature structures covering 94‐120 km,12°S‐39°N latitude are reportedFirst UFKW wind profiles in the 100‐280 km altitude dissipative regime are reportedFirst contemporaneous measurements of ionosphere response and driving UFKW E‐region dynamo winds are reported [ABSTRACT FROM AUTHOR]