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Coastal oceans, traditionally seen as a conduit for transporting atmospheric carbon dioxide (CO2)-derived anthropogenic carbon (CANT) to open oceans, exhibit complex carbon exchanges at their interface. South China Sea (SCS) exemplifies this complexity, where interactions with the Pacific, particularly through Kuroshio intrusion, challenge the understanding of CANT source and variability in a coastal ocean. Contrary to prevailing paradigm expectations, our high-resolution, long-term data reveal that CANT in the SCS primarily originates from Pacific water injection across the Luzon Strait rather than atmospheric CO2 invasion. Over the past two decades, the SCS has experienced increasing CANT levels, with notable interannual fluctuations driven by El Niño and La Niña events influencing Kuroshio intrusion, generating anomalously high and low CANT inventories, respectively. This highlights an overlooked CANT transport pathway from open to coastal oceans, responsible for cumulative ocean acidification that has already affected coral reefs enriched in the SCS located west of the Coral Triangle. [ABSTRACT FROM AUTHOR]

Mercury is a neurotoxin that, unlike many localized industrial pollutants, spreads globally through atmospheric transport. Mercury in the atmosphere is operationally partitioned into gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM), and particulate-bound mercury (TPM). Although GOM makes up only a small fraction of Hg in the free troposphere under normal conditions, its role in the dry and wet deposition of mercury makes GOM a significant species for understanding the transport and fate of mercury in the atmosphere. Although instruments for atmospheric mercury speciation are commercially available, significant uncertainty is associated with the current speciation methods, from sample collection to calibration, for GOM measurements. This paper examines the custom-made calibration sources that have been developed for GOM measuring instruments, evaluates the factors influencing the source performance, and synthesizes recommendations for the design and operation of GOM calibration sources in the future. [ABSTRACT FROM AUTHOR]

Carbon monoxide (CO) is a regulated air pollutant that impacts tropospheric chemistry and is an important indicator of the incomplete combustion of carbon-based fuels. In this study, we used 4 years (2019–2022) of winter and spring (January–May) atmospheric CO observations to quantify and characterize city-scale CO enhancements (Δ CO) from the New York City metropolitan area (NYCMA). We observed large variability in Δ CO, roughly 60 % of which was explained by atmospheric transport from the surrounding surface areas to the measurement sites, with the remaining 40 % due to changes in emissions on sub-monthly timescales. We evaluated the CO emissions from the Emissions Database for Global Atmospheric Research (EDGAR), which has been used to scale greenhouse gas emissions, and found the emissions are much too low in magnitude. During the COVID-19 shutdown in spring 2020, we observed a flattening of the diurnal pattern of CO emissions, consistent with reductions in daytime transportation. Our results highlight the role of meteorology in driving the variability in air pollutants and show that the transportation sector is unlikely to account for the non-shutdown observed CO emission magnitude and variability, an important distinction for determining the sources of combustion emissions in urban regions like the NYCMA. [ABSTRACT FROM AUTHOR]

In this study, the concentrations of cadmium (Cd), iron (Fe), manganese (Mn), nickel (Ni), lead (Pb) and zinc (Zn) in plants sampled from Mt. Madra were investigated. Furthermore, the distribution characteristics and source identification of potentially toxic metals were investigated with the application of Positive Matrix Factorization (PMF) modelling. Samples of 26 different plant species were taken from Mt. Madra at elevations ranging from 177 to 1347 m using the multi-point sampling approach. The metal quantities measured by ICP-OES are the following sequences (mean ± SD) (mg/kg): Fe (974.96 ± 29.6) > Mn (111.81 ± 2.6) > Zn (27.28 ± 0.2) > Ni (2.17 ± 0.03) > Pb (0.77 ± 0.01) > Cd (0.12 ± 0.01). According to the plant samples in which the highest values were determined, the metals are as follows: Cd (Lathyrus laxiflorus, 0.401 mg/kg), Fe (Ajuga orientalis, 7621.207 mg/kg), Mn (Castanea sativa, 724.927 mg/kg), Ni (Prunella laciniata, 6.947 mg/kg), Pb (Crataegus stevenii, 3.955 mg/kg) and Zn (Prunella laciniata, 50.802 mg/kg). The results of the PMF model showed that Cd had an atmospheric transport factor originated and transported from industrial activites, Ni had a substrate factor, Fe, Mn, Pb and Zn were influenced by different anthropogenic factors. [ABSTRACT FROM AUTHOR]

With dry deposition and below-cloud scavenging, in-cloud scavenging is one of the three components of aerosol transfer from the atmosphere to the ground. There is no experimental validation of in-cloud particle scavenging models for all cloud types that is not impacted by uncertainties concerning below-cloud scavenging. In this article, the choice was made to start with a recognised and validated microphysical cloud formation model (the DEtailed SCAvenging Model, DESCAM) to extract a scheme of aerosol scavenging by clouds, valid for different cloud types. The resulting model works for the two most extreme precipitation clouds: from cumulonimbus to stratus. It is based on data accessible a priori from numerical weather prediction (NWP) outputs, i.e. the intensity of the rain and the relative humidity in the cloud. The diagnostic of the altitude of the cloud base proves to be a key parameter, and accuracy in this regard is vital. This new in-cloud scavenging scheme is intended for use in long-distance (> 100 km) atmospheric transport models (ATMs) or global climate models (GCMs). [ABSTRACT FROM AUTHOR]

Marine heatwaves (MHWs) are anomalously warm events that profoundly affect climate change and local ecosystem. During the summer of 2012 (June-September), intense MHWs occurred in the tropical Indian Ocean (TIO) concurrently with an unseasonable positive Indian Ocean Dipole (pIOD) event. The MHW metrics (duration, frequency, cumulative intensity and maximum intensity) were characterized by northwestward-slanted patterns from west Australia to the Somalia coast. The analysis confirmed that these MHWs were closely associated with the unseasonable pIOD 2012. The weakening of Western North Pacific Subtropical High and strengthening of Australian High in spring induced an interhemispheric pressure gradient that drove two anticyclonic circulation patterns over the eastern TIO. The first anticyclonic circulation featured cross-equatorial wind anomalies from south of Java to the South China Sea/Philippine Sea, which led to strong upwelling off Sumatra-Java during the subsequent summer. The second anticyclonic circulation excited downwelling Rossby waves that propagated from the southeastern TIO to the western TIO. Thus, downwelling in the western pole and upwelling in the eastern pole led to a strong pIOD event peaking in summer, namely, the unseasonable pIOD 2012. These downwelling Rossby waves deepened the thermocline by more than 60 m and caused anomalous surface warming, thereby contributing to the occurrences of MHWs. With the development and peak of the unseasonable pIOD 2012, anomalous atmospheric circulation transported moisture from the TIO to the subtropical Western North Pacific (WNP), favoring a strong cyclonic anomaly that profoundly affected the summer monsoon rainfall over the subtropical WNP. This study provides some perspectives on the role of pIOD events in summer climate over the Indo-Northwest Pacific region. [ABSTRACT FROM AUTHOR]

Open biomass burning (OBB) significantly affects regional and global air quality, the climate, and human health. The burning of forests, shrublands, grasslands, peatlands, and croplands influences OBB. A global emissions inventory based on satellite fire detection enables an accurate estimation of OBB emissions. In this study, we developed a global high-resolution (1km×1km) daily OBB emission inventory using the Chinese Fengyun-3D satellite's global fire spot monitoring data, satellite-derived biomass data, vegetation-index-derived spatiotemporally variable combustion efficiencies, and land-type-based emission factors. The average annual estimated OBB emissions for 2020–2022 were 2586.88 Tg C, 8841.45 Tg CO2 , 382.96 Tg CO, 15.83 Tg CH4 , 18.42 Tg NOx , 4.07 Tg SO2 , 18.68 Tg particulate organic carbon (OC), 3.77 Tg particulate black carbon (BC), 5.24 Tg NH3 , 15.85 Tg NO2 , 42.46 Tg PM 2.5 and 56.03 Tg PM 10. Specifically, taking carbon emissions as an example, the average annual estimated OBBs for 2020–2022 were 72.71 (Boreal North America, BONA), 165.73 (Temperate North America, TENA), 34.11 (Central America, CEAM), 42.93 (Northern Hemisphere South America, NHSA), 520.55 (Southern Hemisphere South America, SHSA), 13.02 (Europe, EURO), 8.37 (Middle East, MIDE), 394.25 (Northern Hemisphere Africa, NHAF), 847.03 (Southern Hemisphere Africa, SHAF), 167.35 (Boreal Asia, BOAS), 27.93 (Central Asia, CEAS), 197.29 (Southeast Asia, SEAS), 13.20 (Equatorial Asia; EQAS), and 82.38 (Australia and New Zealand; AUST) TgCyr-1. Overall, savanna grassland burning contributed the largest proportion of the annual total carbon emissions (1209.12 TgCyr-1 ; 46.74 %), followed by woody savanna/shrubs (33.04 %) and tropical forests (12.11 %). SHAF was found to produce the most carbon emissions globally (847.04 TgCyr-1), followed by SHSA (525.56 TgCyr-1), NHAF (394.26 TgCyr-1), and SEAS (197.30 TgCyr-1). More specifically, savanna grassland burning was predominant in SHAF (55.00 %, 465.86 TgCyr-1), SHSA (43.39 %, 225.86 TgCyr-1), and NHAF (76.14 %, 300.21 TgCyr-1), while woody savanna/shrub fires were dominant in SEAS (51.48 %, 101.57 TgCyr-1). Furthermore, carbon emissions exhibited significant seasonal variability, peaking in September 2020 and August of 2021 and 2022, with an average of 441.32 TgCmonth-1 , which is substantially higher than the monthly average of 215.57 TgCmonth-1. Our comprehensive high-resolution inventory of OBB emissions provides valuable insights for enhancing the accuracy of air quality modeling, atmospheric transport, and biogeochemical cycle studies. The GEIOBB dataset can be downloaded at http://figshare.com (last access: 30 July 2024) with the following DOI: 10.6084/m9.figshare.24793623.v2 (Liu et al., 2023). [ABSTRACT FROM AUTHOR]

Accurate real-time forecasts of atmospheric plume behavior are crucial for effective management of environmental release incidents. However, the computational demands of weather simulations and particle transport codes limit their applicability during emergencies. In this study, we employ a U-Net enhanced Fourier Neural Operator (U-FNO) to statistically emulate the calculations of the WSPEEDI dose forecasting numerical simulator, using pre-calculated ensemble simulations. The developed emulator is capable of effectively simulating any radioactive-release scenario and generating the time series of dose distribution in the environment 4000 times faster than the numerical simulator, while still maintaining high accuracy. It predicts the plume direction, extent, and dose-rate magnitudes using initial- and boundary-condition meteorological data as input. The speed and efficiency of this framework offers a powerful tool for swift decision-making during emergencies, facilitating risk-informed protective actions, evacuation execution, and zone delineation. Its application extends to various contaminant release and transport problems, and can be instrumental in engineering tasks requiring uncertainty quantification (UQ) for environmental risk assessment. [ABSTRACT FROM AUTHOR]

This paper examines the linear relationship between climate events in the La Plata Basin (LP) from 1980 to 2018 and atmospheric moisture transport from major sources using a Lagrangian approach. The standardized precipitation evapotranspiration index (SPEI-1) was utilized to assess climate events, as monthly water balance variations may be related to changes in atmospheric moisture transport. A total of 49 dry and 46 wet events were identified through sequences of negative and positive SPEI-1 values, respectively. Lagrangian analysis tracked changes in moisture uptake and supply from sources to the LP during these events. Simple linear regression analysis revealed a relationship between moisture transport from the Amazonas (AM), North Atlantic (NA), and Tocantins (TO) basins and the severity and duration of climate events. Increased moisture supply from the São Francisco basin (SF) and Eastern Brazil oceanic (EBO) sources intensified the duration and severity of wet events. Peak wet events were linked to increased moisture supply from the northern South America basins (AM, NA, and TO), while peak droughts were related to decreased moisture uptake from eastern sources (TO, SF, and EBO). Our findings highlight how the water balance in distant regions affects the LP via moisture transport, emphasizing the need for interconnected adaptive strategies. [ABSTRACT FROM AUTHOR]

Atmospheric moisture transport is crucial for understanding New Zealand's climate dynamics, particularly with respect to extreme precipitation events. While the majority of previous studies have focussed on Atmospheric Rivers (ARs), this study examines the entire spectrum of water vapour transport and its link to extreme precipitation using 40 years (1981–2020) of Integrated Water Vapour Transport (IVT) data over the region. Although ARs are important drivers of extreme precipitation, they are infrequent as they account for less than 10% of total moisture transport at most coastal locations. Extreme water vapour transport (defined by the 90th percentile IVT threshold) corresponds more closely with precipitation extremes than ARs alone, even using an expanded AR detection range. Here, IVT is classified into strength categories from weak to strong. Over the study period, all but the weakest category of IVT has increased in frequency of occurrence over most of the South Island, while decreasing in northern North Island. Similarly, monthly IVT anomaly trends show a positive trend in the South Island and negative trend in the northern North Island during warmer months. Separate analysis of moisture weighted wind speeds (UV) and total column water vapour (TCWV) revealed that even though the dynamic component of IVT has decreased in many locations, the increase in TCWV across New Zealand is the driving factor underpinning the IVT trends. Correspondingly, these findings indicate the importance of analysis both dynamic and thermodynamic factors in seeking to understand hydrometeorological variation and when investigating the responses to climate change. [ABSTRACT FROM AUTHOR]

New particle formation (NPF) substantially affects the global radiation balance and climate. Iodic acid (IA) is a key marine NPF driver that recently has also been detected inland. However, its impact on continental particle nucleation remains unclear. Here, we provide molecular-level evidence that IA greatly facilitates clustering of two typical land-based nucleating precursors: dimethylamine (DMA) and sulfuric acid (SA), thereby enhancing particle nucleation. Incorporating this mechanism into an atmospheric chemical transport model, we show that IA-induced enhancement could realize an increase of over 20% in the SA-DMA nucleation rate in iodine-rich regions of China. With declining anthropogenic pollution driven by carbon neutrality and clean air policies in China, IA could enhance nucleation rates by 1.5 to 50 times by 2060. Our results demonstrate the overlooked key role of IA in continental NPF nucleation and highlight the necessity for considering synergistic SA-IA-DMA nucleation in atmospheric modeling for correct representation of the climatic impacts of aerosols. [ABSTRACT FROM AUTHOR]

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

Atmospheric sensitivities (gradients), quantifying the atmospheric response to emissions or other perturbations, can provide meaningful insights on the underlying atmospheric chemistry or transport processes. Atmospheric adjoint modeling enables the calculation of receptor-oriented sensitivities of model outputs of interest to input parameters (e.g., emissions), overcoming the numerical cost of conventional (forward) modeling. The adjoint of the GEOS-Chem atmospheric chemistry-transport model is a widely used such model, but prior to v36 it lacked extensive stratospheric capabilities. Here, we present the development and evaluation of the discrete adjoint of the global chemistry-transport model (CTM) GEOS-Chem unified chemistry extension (UCX) for stratospheric applications, which extends the existing capabilities of the GEOS-Chem adjoint to enable the calculation of sensitivities that include stratospheric chemistry and interactions. This development adds 37 new tracers, 273 kinetic and photolysis reactions, an updated photolysis scheme, treatment of stratospheric aerosols, and all other features described in the original UCX paper. With this development the GEOS-Chem adjoint model is able to capture the spatial, temporal, and speciated variability in stratospheric ozone depletion processes, among other processes. We demonstrate its use by calculating 2-week sensitivities of stratospheric ozone to precursor species and show that the adjoint captures the Antarctic ozone depletion potential of active halogen species, including the chlorine activation and deactivation process. The spatial variations in the sensitivity of stratospheric ozone to NO x emissions are also described. This development expands the scope of research questions that can be addressed by allowing stratospheric interactions and feedbacks to be considered in the tropospheric sensitivity and inversion applications. [ABSTRACT FROM AUTHOR]

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

Natural aerosols are an important, yet understudied, part of the Arctic climate system. Natural marine biogenic aerosol components (e.g., methanesulfonic acid, MSA) are becoming increasingly important due to changing environmental conditions. In this study, we combine in situ aerosol observations with atmospheric transport modeling and meteorological reanalysis data in a data-driven framework with the aim to (1) identify the seasonal cycles and source regions of MSA, (2) elucidate the relationships between MSA and atmospheric variables, and (3) project the response of MSA based on trends extrapolated from reanalysis variables and determine which variables are contributing to these projected changes. We have identified the main source areas of MSA to be the Atlantic and Pacific sectors of the Arctic. Using gradient-boosted trees, we were able to explain 84% of the variance and find that the most important variables for MSA are indirectly related to either the gas- or aqueous-phase oxidation of dimethyl sulfide (DMS): shortwave and longwave downwelling radiation, temperature, and low cloud cover. We project MSA to undergo a seasonal shift, with non-monotonic decreases in April/May and increases in June-September, over the next 50 years. Different variables in different months are driving these changes, highlighting the complexity of influences on this natural aerosol component. Although the response of MSA due to changing oceanic variables (sea surface temperature, DMS emissions, and sea ice) and precipitation remains to be seen, here we are able to show that MSA will likely undergo a seasonal shift solely due to changes in atmospheric variables. [ABSTRACT FROM AUTHOR]

Flame retardants, widely used in industry as chemicals in additives for consumer products such as electronics, automobiles, polyurethane foams, and textiles, are used to reduce the likelihood of fire in flammable materials. Traditional flame retardants such as polybrominated diphenyl ethers have been proved to have environmental pollution and toxicity problems in several studies, and in order to solve these problems, a series of new flame retardants (NBFRs), represented by decabromodiphenyl ethane (DBDPE), have emerged. As a kind of new pollutant, NBFRs have been reported in industrially developed regions such as the Bohai Rim and Beijing-Tianjin-Hebei regions, as well as in remote regions such as the bipolar regions. As the third pole of the world, the Tibetan Plateau, with low industrialization and sparsely populated, is an important region to study the atmospheric long-range transport and environmental impacts of NBFRs, as is the case for the bipolar regions. In this paper, we summarize the NBFRs studies conducted in the Tibetan Plateau region in recent years, including soil, moss, atmosphere, and water media, and the study area covers a number of typical regions in the Tibetan Plateau. The concentration and detection rate of DBDPE have been reported to be the highest in all matrices on the Tibetan Plateau. However, few studies have been conducted on the Tibetan Plateau and further research is needed to fill the gap of new contaminants in the region. [ABSTRACT FROM AUTHOR]

Atmospheric transport and dispersion models (ATDMs) are widely used to study and forecast pollution events. In the frame of the "Effect of Megacities on the transport and transformation of pollutants on the regional to global scales" (EMeRGe) project, ATDM forecasts were carried out to identify potential airborne sampling areas of perfluorocarbons (PFCs) emanating from controlled PFC releases. The forecasts involved short-distance transport over small-scale topographic maxima (Manilla; Philippines), short-distance transport over large-scale topographic maxima (Taipei, Taiwan) and long-distance transport over mixed topography (Nanjing, China, sampled over Taiwan). In situ aircraft measurements of PFC mixing ratios down to a few parts per quadrillion (ppqv) provide us with a unique dataset to explore the added benefits of dynamical downscaling. Transport simulations were repeated using FLEXPART driven by ERA5 and IFS meteorological data and FLEXPART-WRF with dynamically downscaled IFS data down to 1.1 km and four PBL parametrisations. Of the three cases studied, dynamical downscaling led to significant differences for the Manilla and Taipei releases that can be interpreted through changes in the modelled orographic flow regimes. The choice of PBL scheme also significantly impacted accuracy, but there was no systematically better-performing option, highlighting the benefits of ensemble forecasting. Results show how convergence and divergence between ensemble members can be utilised to help decision-making during field campaigns. This study highlights the role that dynamical downscaling can play as an important component in campaign planning when dealing with observations over orographically complex areas. [ABSTRACT FROM AUTHOR]

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

How air masses transform during meridional transport into and out of the Arctic is not well represented by numerical models. The airborne field campaign HALO- (AC)3 applied the High Altitude and Long-range Research Aircraft (HALO) within the framework of the collaborative research project on Arctic amplification (AC)3 to address this question by providing a comprehensive observational basis. The campaign took place from 7 March to 12 April 2022 in the North Atlantic sector of the Arctic, a main gateway of atmospheric transport into and out of the Arctic. Here, we investigate to which degree the meteorological and sea ice conditions during the campaign align with the long-term climatology (1979–2022). For this purpose, we use the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis v5 (ERA5), satellite data, and measurements at Ny-Ålesund, including atmospheric soundings. The observations and reanalysis data revealed two distinct periods with different weather conditions during HALO- (AC)3 : the campaign started with a warm period (11–20 March 2022) where strong southerly winds prevailed that caused poleward transport of warm and moist air masses, so-called moist and warm air intrusions (WAIs). Two WAI events were identified as atmospheric rivers (ARs), which are narrow bands of strong moisture transport. These warm and moist air masses caused the highest measured 2 m temperatures (5.5 °C) and daily precipitation rates (42 mm d -1) at Ny-Ålesund for March since the beginning of the record (1993). Over the sea ice northwest of Svalbard, ERA5 indicated record-breaking rainfall. After the passage of a strong cyclone on 21 March 2022, a cold period followed. Northerly winds advected cold air into the Fram Strait, causing marine cold air outbreaks (MCAOs) until the end of the campaign. This second phase included one of the longest MCAO events found in the ERA5 record (19 d). On average, the entire campaign period was warmer than the climatological mean due to the strong influence of the ARs. In the Fram Strait, the sea ice concentration was well within the climatological variability over the entire campaign duration. However, during the warm period, a large polynya opened northeast of Svalbard, untypical for this season. Compared to previous airborne field campaigns focusing on the evolution of (mixed-phase) clouds, a larger variety of MCAO conditions was observed during HALO- (AC)3. In summary, air mass transport into and out of the Arctic was more pronounced than usual, providing exciting prospects for studying air mass transformation using HALO- (AC)3. [ABSTRACT FROM AUTHOR]

Atmospheric volatile organic compounds (VOCs) constitute a wide range of species, acting as precursors to ozone and aerosol formation. Atmospheric chemistry and transport models (CTMs) are crucial to understanding the emissions, distribution, and impacts of VOCs. Given the uncertainties in VOC emissions, lack of evaluation studies, and recent changes in emissions, this work adapts the European Monitoring and Evaluation Programme Meteorological Synthesizing Centre – West (EMEP MSC-W) CTM to evaluate emission inventories in Europe. Here we undertake the first intensive model–measurement comparison of VOCs in 2 decades. The modelled surface concentrations are evaluated both spatially and temporally, using measurements from the regular EMEP monitoring network in 2018 and 2019, as well as a 2022 campaign. To achieve this, we utilised the UK National Atmospheric Emissions Inventory to derive explicit emission profiles for individual species and employed a tracer method to produce pure concentrations that are directly comparable to observations. The degree to which the modelled and measured VOCs agree varies depending on the specific species. The model successfully captures the overall spatial and temporal variations of major alkanes (e.g. ethane, n -butane) and unsaturated species (e.g. ethene, benzene) but less so for propane, i -butane, and ethyne. This discrepancy underscores potential issues in the boundary conditions for the latter species and in their primary emissions from, in particular, the solvent and road transport sectors. Specifically, potential missing propane emissions and issues with its boundary conditions are highlighted by large model underestimations and smaller propane-to-ethane ratios compared to the measurement. Meanwhile, both the model and measurements show strong linear correlations among butane isomers and among pentane isomers, indicating common sources for these pairs of isomers. However, modelled ratios of i -butane to n -butane and i -pentane to n -pentane are approximately one-third of the measured ratios, which is largely driven by significant emissions of n -butane and n -pentane from the solvent sector. This suggests issues with the speciation profile of the solvent sector, underrepresented contributions from transport and fuel evaporation sectors in current inventories, or both. Furthermore, the modelled ethene-to-ethyne and benzene-to-ethyne ratios differ significantly from measured ratios. The different model performance strongly points to shortcomings in the spatial and temporal patterns and magnitudes of ethyne emissions, especially during winter. For OVOCs, the modelled and measured concentrations of methanal and methylglyoxal show a good agreement, despite a moderate underestimation by the model in summer. This discrepancy could be attributed to an underestimation of contributions from biogenic sources or possibly a model overestimation of their photolytic loss in summer. However, the insufficiency of suitable measurements limits the evaluation of other OVOCs. Finally, model simulations employing the CAMS inventory show slightly better agreements with measurements than those using the Centre on Emission Inventories and Projections (CEIP) inventory. This enhancement is likely due to the CAMS inventory's detailed segmentation of the road transport sector, including its associated sub-sector-specific emission profiles. Given this improvement, alongside the previously mentioned concerns about the model's biased estimations of various VOC ratios, future efforts should focus on a more detailed breakdown of dominant emission sectors (e.g. solvents) and the refinement of their speciation profiles to improve model accuracy. [ABSTRACT FROM AUTHOR]

Carbon dioxide (CO 2) is a crucial greenhouse gas, and its concentration and spatiotemporal characteristics are among the principal sources of uncertainty in global warming assessments. Satellite remote sensing is a widely adopted, high-accuracy approach for monitoring atmospheric CO 2. However, limited swath width and cloud cover significantly reduce satellite observation coverage. This study addresses the temporal changes in CO 2 concentration and utilizes a machine learning-based fusion of multiple data sources to generate daily, full-coverage, 0.05° spatial resolution column-averaged CO 2 concentration data for China from 2015 to 2020. Ten-fold cross-validation yielded a determination coefficient R2 of 0.97, root mean square error of 0.92 ppm, and mean absolute error of 0.59 ppm. Compared to other datasets, this study's dataset exhibits superior accuracy and spatiotemporal detail. Using the produced CO 2 concentration data in this study, we conducted a spatiotemporal analysis of CO 2 concentrations in China. The results indicate that, in general, the Western region exhibits a higher growth rate in CO 2 concentration than the Eastern and Central regions, with areas of lower CO 2 concentration experiencing higher growth rates while regions with higher CO 2 concentration have lower growth rates. Moreover, the highest increase in CO 2 concentration occurred in 2016, with a substantial decrease in CO 2 concentration growth observed in 2018. Notably, the reduction in CO 2 concentration in the Qinghai-Tibet Plateau region during the summer is considerably smaller than in other regions, possibly due to atmospheric transport from the Indian Peninsula. [ABSTRACT FROM AUTHOR]

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

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

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

Trace gases and aerosols play a crucial role in shaping Arctic climate through their impacts on radiation and chemistry. The concentration of these substances over the Arctic is largely determined by long-range transport originating from midlatitude and tropical source regions. In this study, we explore how atmospheric circulation modulates the interannual variability of long-range transport into the Arctic by utilizing a chemistry–climate model. Idealized tracers, which have fixed lifetimes and spatially varying but temporally fixed surface emissions corresponding to the climatology of anthropogenic emissions of the year 2000, are employed to isolate the role of atmospheric transport from emission and chemistry in modulating interannual variability. Tracers emitted from different source regions are tagged to quantify their relative contributions. Model simulations reveal that tracers from Europe, East Asia, and North America contribute the most to Arctic tracer mass, followed by those from the Tibetan Plateau and South Asia, as well as the Middle East. These regional tracers are predominantly transported into the Arctic middle to upper troposphere, with the exception of tracers from Europe during winter, which are transported into the Arctic lower troposphere. Our analysis shows that the interannual variability of transport into the Arctic for each regional tracer is determined by the atmospheric circulation over the corresponding emission region; i.e., anomalous poleward and eastward winds over the source region promote transport into the Arctic. Considering tracers with global emissions, a southward shift of the midlatitude jet during winter favors increased transport into the Arctic, particularly for tracers emitted over Asia, aligning with previous studies. Comparisons of tracers with different lifetimes indicate that the interannual variability of shorter lifetime tracers is predominantly influenced by regional tracers with shorter transport pathways into the Arctic (e.g., Europe), while the interannual variability of longer lifetime tracers is more contributed by regional tracers with higher emissions (e.g., East Asia). [ABSTRACT FROM AUTHOR]

Arctic Amplification (AA), the amplified surface warming in the Arctic relative to the globe, is a salient feature of climate change. While the basic physical picture of AA has been depicted, how its degree is determined has not been clearly understood. Here, by deciphering atmospheric heat transport (AHT), we build a two-box energy-balance model of AA and derive that the degree of AA is a simple nonlinear function of the Arctic and global feedbacks, the meridional heterogeneity in radiative forcing, and the partial sensitivities of AHT to global mean and meridional gradient of warming. The formula captures the varying AA in climate models and attributes the spread to models' feedback parameters and AHT physics. The formula clearly illustrates how essential physics mutually determine the degree of AA and limits its range within 1.5-3.5. Our results articulate AHT as both forcing and feedback to AA, highlight its fundamental role in forming a baseline AA that exists even with uniform feedbacks, and underscore its partial sensitivities instead of its total change as key parameters of AA. The lapse-rate feedback has been widely recognized as a major contributor to AA but its effect is fully offset by the water-vapor feedback. The authors show that the degree of amplified warming in the Arctic relative to the rest of the globe can be analytically understood from a simple nonlinear formula of five key physical parameters. [ABSTRACT FROM AUTHOR]

Carbon monoxide (CO) is a prominent air pollutant in cities, with far-reaching implications for both local air quality and global atmospheric chemistry. The long-term change in atmospheric CO levels at a specific location is influenced by a complex interplay of local emissions, atmospheric transport, and photochemical processes, making it a subject of considerable interest. This study presents an 8-year analysis (2014–2021) of in situ CO observations using a cutting-edge laser-based analyzer at an urban site in Ahmedabad, western India. The long-term observations reveal a subtle trend in CO levels, masked by contrasting year-to-year variations, particular after 2018, across distinct diurnal time windows. Mid-afternoon (12:00–16:00 h) CO levels, reflecting background and regional conditions, remained relatively stable over the study period. In contrast, evening (18:00–21:00 h) CO levels, influenced by local emissions, exhibited substantial inter-annual variability without discernible trends from 2014 to 2018. However, post-2018, evening CO levels showed a consistent decline, predating COVID-19 lockdown measures. This decline coincided with the nationwide adoption of Bharat stage IV emission standards and other measures aimed at reducing vehicular emissions. The COVID-19 lockdown in 2020 further resulted in a noteworthy 29% reduction in evening CO levels compared to the pre-lockdown (2014–2019) period, highlighting the potential for substantial CO reduction through stringent vehicular emission controls. The observed long-term changes in CO levels do not align with the decreasing emission estimated by various inventories from 2014 to 2018, suggesting a need for improved emission statistics in Indian urban regions. This study underscores the importance of ongoing continuous CO measurements in urban areas to inform policy efforts aimed at controlling atmospheric pollutants. [ABSTRACT FROM AUTHOR]

In Southern Mediterranean regions, the issue of summer fires related to agriculture practices is a periodic recurrence. It implies a significant increase in carbon dioxide (CO2) emissions and other combustion-related gaseous and particles compounds emitted into the atmosphere with potential impacts on air quality and global climate. In this work, we performed an analysis of summer fire events that occurred on August 2021. Measurements were carried out at the permanent World Meteorological Organization (WMO)/Global Atmosphere Watch (GAW) station of Lamezia Terme (Code: LMT) in Calabria, Southern Italy. The observatory is equipped with greenhouse gases and black carbon analyzers, an atmospheric particulate impactor system, and a meteo-station for atmospheric parameters to characterize atmospheric mechanisms and transport for land and sea breezes occurrences. High mole fractions of carbon monoxide (CO) and carbon dioxide (CO2) coming from quadrants of inland areas were correlated with fire counts detected via the MODIS satellite (GFED-Global Fire Emissions Database) at 1 km of spatial resolution. In comparison with the typical summer values, higher CO and CO2 were observed in August 2021. Furthermore, the growth in CO concentration values in the tropospheric column was also highlighted by the analyses of the L2 products of the Copernicus SP5 satellite. Wind fields were reconstructed via a Weather Research and Forecasting (WRF) output, the latter suggesting a possible contribution from open fire events observed at the inland region near the observatory. So far, there have been no documented estimates of the effect of prescribed burning on carbon emissions in this region. This study suggested that data collected at the LMT station can be useful in recognizing and consequently quantifying emission sources related to open fires. [ABSTRACT FROM AUTHOR]

Human activities have increased atmospheric emissions and deposition of oxidized and reduced forms of nitrogen, but emission control programs have largely focused on oxidized nitrogen. As a result, in many regions of the world emissions of oxidized nitrogen are decreasing while emissions of reduced nitrogen are increasing. Emissions of reduced nitrogen largely originate from livestock waste and fertilizer application, with contributions from transportation sources in urban areas. Observations suggest a discrepancy between trends in emissions and deposition of reduced nitrogen in the U.S., likely due to an underestimate in emissions. In the atmosphere, ammonia reacts with oxides of sulfur and nitrogen to form fine particulate matter that impairs health and visibility and affects climate forcings. Recent reductions in emissions of sulfur and nitrogen oxides have limited partitioning with ammonia, decreasing long-range transport. Continuing research is needed to improve understanding of how shifting emissions alter formation of secondary particulates and patterns of transport and deposition of reactive nitrogen. Satellite remote sensing has potential for monitoring atmospheric concentrations and emissions of ammonia, but there remains a need to maintain and strengthen ground-based measurements and continue development of chemical transport models. Elevated nitrogen deposition has decreased plant and soil microbial biodiversity and altered the biogeochemical function of terrestrial, freshwater, and coastal ecosystems. Further study is needed on differential effects of oxidized versus reduced nitrogen and pathways and timescales of ecosystem recovery from elevated nitrogen deposition. Decreases in deposition of reduced nitrogen could alleviate exceedances of critical loads for terrestrial and freshwater indicators in many U.S. areas. The U.S. Environmental Protection Agency should consider using critical loads as a basis for setting standards to protect public welfare and ecosystems. The U.S. and other countries might look to European experience for approaches to control emissions of reduced nitrogen from agricultural and transportation sectors. Implications: In this Critical Review we synthesize research on effects, air emissions, environmental transformations, and management of reduced forms of nitrogen. Emissions of reduced nitrogen affect human health, the structure and function of ecosystems, and climatic forcings. While emissions of oxidized forms of nitrogen are regulated in the U.S., controls on reduced forms are largely absent. Decreases in emissions of sulfur and nitrogen oxides coupled with increases in ammonia are shifting the gas-particle partitioning of ammonia and decreasing long-range atmospheric transport of reduced nitrogen. Effort is needed to understand, monitor, and manage emissions of reduced nitrogen in a changing environment. [ABSTRACT FROM AUTHOR]

Fine-scale models for the transport of marine aerosols are of great interest for the study of micro-climates and air quality in areas of complex topography, such as in urbanized coastal areas. To this end, the MIO laboratory implemented the Meso-NH model in its LES version over the northwest Mediterranean coastal zone using a recent sea-spray source function. Simulated meteorological parameters and aerosol concentrations are compared to experimental data acquired in the Mediterranean coastal zone in spring 2008 on board the R/V Atalante. Key findings indicate that the large eddy simulation (LES) mode closely matches with the experimental data, enabling an in-depth analysis of the numerical model ability to predict variations in aerosol concentrations. These variations are influenced by different wind directions, which lead to various fetch distances typical of coastal zones. [ABSTRACT FROM AUTHOR]

Based on the Weather Research and Forecasting Model Coupled with Chemistry (WRF-Chem) atmospheric chemistry model, a parameterization scheme for the radioactive isotope caesium (137Cs), considering processes such as advection, turbulent diffusion, dry deposition, and wet deposition, was constructed, enabling the spatial distribution simulation of the concentration and deposition of 137Cs. The experimental simulation studies were carried out during the high emission period of the Fukushima nuclear accident (from 11 to 17 March 2011). Two sets of comparison experiments, with or without deposition, were designed, the effects of wind field and precipitation on the spatial transport and ground deposition of 137Cs were analyzed, and the influence of wind field and precipitation on 137Cs vertical transport was analyzed in detail. The results indicate that the model can accurately simulate the meteorological and 137Cs variables. On 15 March, 137Cs dispersed towards the Kanto Plain in Japan under the influence of northeastern winds. In comparison to the experiment without deposition, the concentration of 137Cs in the Fukushima area decreased by approximately 286 Bq·m−3 in the deposition experiment. Under the influence of updrafts in the non-deposition experiment, a 137Cs cloud spread upward to a maximum height of 6 km, whereas in the deposition experiment, the highest dispersion of the 137Cs cloud only reach a height of 4 km. Affected by the wind field, dry deposition is mainly distributed in Fukushima, the Kanto Plain, and their eastern ocean areas, with a maximum dry deposition of 5004.5 kBq·m−2. Wet deposition is mainly influenced by the wind field and precipitation, distributed in the surrounding areas of Fukushima, with a maximum wet deposition of 725.3 kBq·m−2. The single-station test results from the deposition experiment were better than those for the non-deposition experiment: the percentage deviations of the Tokyo, Chiba, Maebashi, and Naraha stations decreased by 61%, 69%, 46%, and 51%, respectively, and the percentage root mean square error decreased by 46%, 25%, 38%, and 48%, respectively. [ABSTRACT FROM AUTHOR]

Priority 16 polycyclic aromatic hydrocarbons were examined in the surface water from urbanized rivers and drains. The concentration in the Hindon River, Yamuna River, and drains, respectively, varied from 1.64 to 73.4, 1.98 to 93.0, and 1.99 to 67.4 µg L−1. Total concentrations of PAHs in winter were 4.1, 2.9, and 3.6 times higher than in summer, respectively. Naphthalene, acenaphthylene, fluorene, (low molecular weight compounds) and chrysene contributed 62.3% to 74.4% and 17.7% to 24.8%, respectively, to the overall concentration. Their predominance suggested emissions from the combustion of industrial oil, wood, and grass. Due to the impact of waste water discharges, the spatial distribution was unpredictable. In comparison to the lower section of the rivers, the upper stretch had a low concentration. This suggested that it came from sources of urban emissions. Emission sources from unintentional spills and auto shops, along with local emissions and long-range atmospheric transport, were found in the source apportionment analysis. Locations where some PAHs surpassed chronic values could be hazardous to aquatic life. A thorough investigation was necessary because there are relatively few studies on persistent organic contaminants, such as polycyclic aromatic hydrocarbons, in surface waters from the area. [ABSTRACT FROM AUTHOR]

The oxygen isotope anomaly (Δ17O = δ17O - 0.52 × δ18O > 0) has proven to be a robust tool for probing photochemical cycling and atmospheric formation pathways of oxidized reactive nitrogen (NOy). Several studies have developed modeling techniques to implicitly model Δ17O of NOy molecules based on numerous assumptions that may not always be valid. Thus, these models may be oversimplified and limit our ability to compare model Δ17O values of NOy with observations. In this work, we introduce a novel method for explicitly tracking Δ17O transfer and propagation into NOy and odd oxygen (Ox), integrated into the Regional Atmospheric Chemistry Mechanism, version 2 (RACM2). Termed ICOIN-RACM2 (InCorporating Oxygen Isotopes of NOy in RACM2), this new model includes the addition of 55 new species and 729 replicate reactions to represent the propagation of Δ17O derived from O3 into NOy and Ox. Employing this mechanism within a box model, we simulate Δ17O for various NOy and Ox molecules for chamber experiments with varying initial nitrogen oxides (NOx = NO + NO2) and α -pinene conditions, revealing response shifts in Δ17O linked to distinct oxidant conditions. Furthermore, diel cycles are simulated under two summertime scenarios, representative of an urban and rural site, revealing pronounced Δ17O diurnal patterns for several NOy components and substantial Δ17O differences associated with pollution levels (urban vs. rural). Overall, the proposed mechanism offers the potential to assess NOy oxidation chemistry in chamber studies and air quality campaigns through Δ17O model comparisons against observations. The integration of this mechanism into a 3-D atmospheric chemistry transport model is expected to notably enhance our capacity to model and anticipate Δ17O across landscapes, consequently refining model representations of atmospheric chemistry and tropospheric oxidation capacity. [ABSTRACT FROM AUTHOR]

Regional weather and climate are generally impacted by global climatic phenomenon′s. Understanding the impact of global climate phenomenon′s on an atmospheric branch of the hydrological cycle is crucial to make advances in skillful precipitation forecast. The present study adopts a multiscale approach based on wavelets for unravelling the linkages between teleconnections and atmospheric moisture transport over homogeneous regions of Indian sub-continent. We investigated linkages between atmospheric moisture transport quantified as monthly integrated water vapor transport (IVT) during 1951–2022 over selected homogeneous regions and eight large scale climate oscillations using wavelet and global wavelet coherence. Our results indicate significant heterogeneity in linkages across different regions and across multiple timescales. In particular, the Indian Ocean Dipole (IOD) influence monthly IVT at intra-annual to inter-annual scale over all regions. The El Niño–Southern Oscillation (ENSO) have strong connection to monthly IVT at inter-annual scale whereas over west central region both IOD and ENSO strongly influence IVT at inter-decadal scale. While the Atlantic Multi-Decadal Oscillation and Pacific Decadal Oscillation have an impact on IVT in the north-east and southern regions, the Arctic Oscillation and North Atlantic oscillation have a strong inter-annual connection to IVT, majorly in the northwest and hilly regions. Overall, the methodology offers an effective approach for capturing the dynamics of atmospheric moisture transport in time–frequency space and provide a practical reference for prediction of atmospheric moisture transport linked precipitation over different regions of Indian subcontinent. [ABSTRACT FROM AUTHOR]

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

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

Remote sensing based on satellites can provide long-term, consistent, and global coverage of NO2 (an important atmospheric air pollutant) as well as other trace gases. However, satellite data often miss data due to factors including but not limited to clouds, surface features, and aerosols. Moreover, one of the longest continuous observational platforms of NO2 observations from space, OMI, has suffered from missing data over certain rows since 2007, significantly reducing spatial coverage. This work uses the OMI based OMNO2 product, as well as an NO2 product from GOME-2 in combination with machine learning (XGBoost) and spatial interpolation (DINEOF) method to produce a 16-year global daily high spatial-temporal coverage merged tropospheric NO2 dataset (HSTCM-NO2, https://doi.org/10.5281/zenodo.10968462 , Qin et al., 2024), which increases the global spatial coverage of NO2 by ~60 % compared to the original OMINO2 data. The HSTCM-NO2 dataset is validated using upward looking observations of NO2 (MAX-DOAS), other satellites (TROPOMI), and reanalysis products. The comparisons show that HSTCM-NO2 maintains a good correlation with the magnitude of other observational datasets, except for under heavily polluted conditions (>6×1015 molec.cm-2). This work also introduces a new validation technique to validate coherent spatial and temporal signals (EOF) and validates that the HSTCM-NO2 are not only consistent with the original OMNO2 data, but in some parts of the world effectively fill in missing gaps and yield a superior result when analyzing long-range atmospheric transport of NO2. The few differences are also reported to be related to areas in which the original OMNO2 signal was very low, which has been shown elsewhere, but not from this perspective, further validating that applying a minimum cutoff to retrieved NO2 data is essential. The reconstructed data product can effectively extend the utilization value of the original OMNO2 data, and the data quality of HSTCM-NO2 can meet the needs of scientific research. [ABSTRACT FROM AUTHOR]

Ignoring the diurnal cycle in surface-to-atmosphere CO2 fluxes leads to a systematic bias in CO2 mole fraction simulations sampled at daytime, because the daily mean flux systematically misses the CO2 uptake during the daytime hours. In an atmospheric inversion using daytime-selected CO2 measurements at most continental sites and not resolving diurnal cycles in the flux, this leads to systematic biases in the estimates of the annual sources and sinks of atmospheric CO2. This study focuses on quantifying the impact of this diurnal cycle effect on the annual carbon fluxes estimated with the CarboScope (CS) atmospheric inversion at regional, continental, and global scales for the period of time 2010–2020. Biogenic fluxes of hourly Net Ecosystem Exchange (NEE) obtained from the data-driven FLUXCOM estimates are used in the inversion together with global and regional atmospheric transport models. Differences between CO2 mixing ratios simulated with daily averaged and hourly NEE range between around -2.5 and 7 ppm averaged annually throughout a site network across the world. As a consequence, these differences lead to systematic biases in CO2 flux estimates when ignoring the diurnal variations of the CO2 flux in the atmospheric inversions. Although the impact on the global average of estimated annual flux is negligible (around 2 % of the overall land flux of -1.79 Pg C yr-1), we find significant biases in the annual flux budgets at continental and regional scales. For Europe, the annual mean difference in the fluxes arising from the diurnal cycle of CO2 represents around 48 % of the annual posterior fluxes (0.31 Pg C yr-1) estimated with CarboScope-Regional (CSR). Furthermore, the differences in NEE estimates calculated with CS increase the magnitude of the flux budgets for some regions such as northern American temperate and northern Africa by a factor of about 1.5. To the extent that FLUXOM diurnal cycles are realistic at all latitudes and for the station set used in our inversions here, we conclude that ignoring the diurnal variations in the land CO2 flux leads to overestimation of both CO2 sources in the tropical lands and CO2 sinks in the temperate zones. [ABSTRACT FROM AUTHOR]

The Arctic is warming up to 4 times faster than the global average, leading to significant environmental changes. Given the sensitivity of natural methane (CH4) sources to environmental conditions, increasing Arctic temperatures are expected to lead to higher CH4 emissions, particularly due to permafrost thaw and the exposure of organic matter. Some estimates therefore assume the existence of an Arctic methane bomb, where vast CH4 quantities are suddenly and rapidly released over several years. This study examines the ability of the in situ observation network to detect such events in the Arctic, a generally poorly constrained region. Using the FLEXPART (FLEXible PARTicle) atmospheric transport model and varying CH4 emission scenarios, we found that areas with a dense observation network could detect a methane bomb occurring within 2 to 10 years. In contrast, regions with sparse coverage would need 10 to 30 years, with potential false positives in other areas. [ABSTRACT FROM AUTHOR]

The Pyrenean Platform for Observation of the Atmosphere (P2OA) is a coupled plain-mountain instrumented platform in southwest France. It is composed of two physical sites: The 'Pic du Midi' mountain top observatory (2877 m a.s.l.) and the 'Centre de Recherches Atmosphériques' (600 m a.s.l). Both sites are complementarily instrumented for the monitoring of climate variables and the study of meteorological processes in a mountainous region. The scientific topics covered by the P2OA include surface-atmosphere interactions in heterogeneous landscape and complex terrain, physics and chemistry of atmospheric trace species at large scale, influence of local and regional-scale emissions and transport on the atmospheric composition, and transient luminous events above thunderstorms. With a large number of instruments and a high hosting capacity, the P2OA contributes to atmospheric sciences in (i) building long-term series of atmospheric observations, (ii) hosting experimental field campaigns and instrumental tests, (iii) educational training in atmospheric observation techniques. Here we present the complete instrumentation of the P2OA and the associated datasets, give a meteorological characterization of the platform, and illustrate the potential of the P2OA and its dataset with past or ongoing studies and projects. [ABSTRACT FROM AUTHOR]

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

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

We investigate historical simulations of relevant components of the Arctic energy and water budgets for 39 Coupled Model Intercomparison Project Phase 6 (CMIP6) models and validate them against observation-based estimates. We look at simulated seasonal cycles, long-term averages and trends of lateral transports and storage rates in atmosphere and ocean as well as vertical fluxes at top-of-atmosphere and the surface. We find large inter-model spreads and systematic biases in the representation of annual cycles and long-term averages. Surface freshwater fluxes associated with precipitation and evaporation as well as runoff from Arctic lands tend to be overestimated by most CMIP6 models and about two thirds of the analysed models feature an early timing bias of one month in the runoff cycle phase, related to an early snow melt bias and the lack of realistic river routing schemes. Further, large biases are found for oceanic volume transports, partly because data required for accurate oceanic transport computations has not been archived. Biases are also present in the simulated energy budget components. The net vertical energy flux out of the ocean at the Arctic surface as well as poleward oceanic heat transports are systematically underestimated by all models. We find strong anti-correlation between average oceanic heat transports and mean sea ice cover, atmospheric heat transports, and also the long-term ocean warming rate. The latter strongly suggests that accurate depiction of the mean state is a prerequisite for realistic projections of future warming of the Arctic. Our diagnostics also provide useful process-based metrics for model selection to constrain projections. [ABSTRACT FROM AUTHOR]

Lagrangian particle dispersion models are indispensable tools for the study of atmospheric transport processes. However, Lagrangian transport simulations can become numerically expensive when large numbers of air parcels are involved. To accelerate these simulations, we made considerable efforts to port the Massive-Parallel Trajectory Calculations (MPTRAC) model to graphics processing units (GPUs). Here we discuss performance optimizations of the major bottleneck of the GPU code of MPTRAC, the advection kernel. Timeline, roofline, and memory analyses of the baseline GPU code revealed that the application is memory-bound, and performance suffers from near-random memory access patterns. By changing the data structure of the horizontal wind and vertical velocity fields of the global meteorological data driving the simulations from structure of arrays (SoAs) to array of structures (AoSs) and by introducing a sorting method for better memory alignment of the particle data, performance was greatly improved. We evaluated the performance on NVIDIA A100 GPUs of the Jülich Wizard for European Leadership Science (JUWELS) Booster module at the Jülich Supercomputing Center, Germany. For our largest test case, transport simulations with 108 particles driven by the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA5 reanalysis, we found that the runtime for the full set of physics computations was reduced by 75 %, including a reduction of 85 % for the advection kernel. In addition to demonstrating the benefits of code optimization for GPUs, we show that the runtime of central processing unit (CPU-)only simulations is also improved. For our largest test case, we found a runtime reduction of 34 % for the physics computations, including a reduction of 65 % for the advection kernel. The code optimizations discussed here bring the MPTRAC model closer to applications on upcoming exascale high-performance computing systems and will also be of interest for optimizing the performance of other models using particle methods. [ABSTRACT FROM AUTHOR]

Within the framework of the Isotopic Constraints on Past Ozone Layer in Polar Ice (ISOL-ICE) project, we present initial ice core results from the new ISOL-ICE ice core covering the last millennium from high-elevation Dronning Maud Land (DML) and discuss the implications for interpreting the stable isotopic composition of nitrogen in ice core nitrate (δ15 N(NO 3-)) as a surface ultra-violet radiation (UV) and total column ozone (TCO) proxy. In the quest to derive TCO using δ15 N(NO 3-), an understanding of past snow accumulation changes, as well as aerosol source regions and present-day drivers of their variability, is required. We therefore report here the ice core age–depth model, the snow accumulation and ice chemistry records, and correlation analysis of these records with climate variables over the observational era (1979–2016). The ISOL-ICE ice core covers the last 1349 years from 668 to 2017 CE ± 3 years, extending previous ice core records from the region by 2 decades towards the present and shows excellent reproducibility with those records. The extended ISOL-ICE record of last 2 decades showed a continuation of the methane sulfonate (MSA -) increase from ∼ 1800 to present while there were less frequent large deposition events of sea salts relative to the last millennium. While our chemical data do not allow us to distinguish the ultimate (sea ice or the open ocean) source of sea salt aerosols in DML winter aerosol, our correlation analysis clearly suggests that it is mainly the variability in atmospheric transport and not the sea ice extent that explains the interannual variability in sea salt concentrations in DML. Correlation of the snow accumulation record with climate variables over the observational era showed that precipitation at ISOL-ICE is predominately derived from the South Atlantic with onshore winds delivering marine air masses to the site. The snow accumulation rate was stable over the last millennium with no notable trends over the last 2 decades relative to the last millennium. Interannual variability in the accumulation record, ranging between 2 and 20 cm a -1 (w.e.), would influence the ice core δ15 N(NO 3-) record. The mean snow accumulation rate of 6.5±2.4 cm a -1 (w.e.) falls within the range suitable for reconstructing surface mass balance from ice core δ15 N(NO 3-), highlighting that the ISOL-ICE ice core δ15 N(NO 3-) can be used to reconstruct either the surface mass balance or surface UV if the ice core δ15 N(NO 3-) is corrected for the snow accumulation influence, thereby leaving the UV imprint in the δ15 N(NO 3-) ice core record to quantify natural ozone variability. [ABSTRACT FROM AUTHOR]

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

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

Propane (C3H8) is an important trace gas in the atmosphere, as it is a proxy for oil and gas production and has a significant impact on atmospheric chemical reactions related to the hydroxyl radical and tropospheric ozone formation. In this study, solar direct absorption spectra near 2967 cm−1 recorded by a ground-based Fourier Transform InfraRed spectrometer (FTIR) are applied to retrieve C3H8 total columns between June 2018 and July 2022 at Xianghe in North China. The systematic and random uncertainties of the C3H8 column retrieval are estimated to be 18.2 % and 18.1 %, respectively. The mean and standard deviation of the C3H8 columns derived from the FTIR spectra at Xianghe are 1.80±0.81(1 σ) × 1015 molecules / cm 2. Good correlations are found between C3H8 and other non-methane hydrocarbons, such as C2H6 (R=0.84) and C2H2 (R=0.79), as well as between C3H8 and CO (R=0.72). However, the correlation between C3H8 and CH4 is relatively weak (R=0.45). The FTIR C3H8 measurements are also compared against two atmospheric chemical transport model simulations (the Whole Atmosphere Community Climate Model (WACCM) and the Copernicus Atmosphere Monitoring Service (CAMS)). We find that the C3H8 columns from both models have different seasonal variations as compared to the FTIR measurements. Moreover, the mean C3H8 columns derived from the WACCM and CAMS models are about 68 % larger than the FTIR retrievals. The new FTIR measurements at Xianghe provide us an insight into the C3H8 column variations and underlying processes in North China. [ABSTRACT FROM AUTHOR]

Acetone is an abundant volatile organic compound (VOC) in the atmosphere, with important influences on ozone and oxidation capacity. Direct sources include chemical production from other VOCs and anthropogenic emissions, terrestrial vegetation, biomass-burning emissions, and ocean production. Sinks include chemical loss, deposition onto the land surface, and ocean uptake. Acetone also has a lifetime that is long enough to allow transport and reactions with other compounds remote from its sources. The NASA Goddard Institute for Space Studies (GISS) Earth system model ModelE2.1 simulates a variety of Earth system interactions. Previously, acetone had a very simplistic representation in the ModelE chemical scheme. This study assesses a more sophisticated acetone scheme in which acetone is a full 3-dimensional tracer with explicit sources, sinks, and atmospheric transport. We first evaluate the new global acetone budget in the context of past literature. Estimated source and sink fluxes fall within the range of previous models, although total atmospheric burden and lifetime are at the lower end of the published literature. Acetone's new representation in ModelE2.1 also results in more realistic spatial and vertical distributions, which we compare against previous models and field observations. The seasonality of acetone-related processes was also studied in conjunction with field measurements, and these comparisons show promising agreement but also shortcomings at high-emission urban locations, where the model's resolution is too coarse to capture the true behavior. Finally, we conduct a variety of sensitivity studies that explore the influence of key parameters on the acetone budget and its global distribution. An impactful finding is that the production of acetone from precursor hydrocarbon oxidation has strong leverage on the overall chemical source, indicating the importance of accurate molar yields. Overall, our implementation is one that corroborates with previous studies and marks a significant improvement in the development of the acetone tracer in GISS ModelE2.1. [ABSTRACT FROM AUTHOR]