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Northeast China (NEC) is one of the most severely impacted regions by fire and biomass burning in the country. Notably, fires in this area have exhibited an increasing trend over the past decade, contrasting with the extensive pollution reduction observed in other parts of China. In this study, we combine observational data analysis and climate model simulations to demonstrate that the escalation of spring fire activities in NEC is likely induced by a decline in Bering Sea ice concentration during preceding months. This Arctic‐driven teleconnection contributes to increased temperatures and decreased precipitation in NEC through reduced vertical wind shear, anomalously northerly wind transport, and the formation of a high‐pressure center with descending airflow. These changes are conducive to fire ignition and expansion. Furthermore, this linkage may be amplified in future warmer scenarios. This mechanism holds significant implications for predicting decadal fire activity and furthering our understanding of global environmental projections. Plain Language Summary In Northeast China (NEC), a region severely impacted by fire and biomass burning, there has been an increasing trend in fires over the past decade. This contrasts with pollution reduction seen in other parts of the country. It is therefore necessary to investigate the potential causes of this trend. Here, we show this increase in spring fires is likely due to a decrease in ice concentration in the Bering Sea during earlier months. The Arctic‐driven teleconnection will increase the temperature and decrease the precipitation in NEC through reduced vertical wind shear, anomalously north wind transport, and the local high‐pressure center with descending airflow. These changes create a hotter and drier condition in NEC that is conducive to fire activities. Furthermore, this connection could be more pronounced in future warmer scenarios, emphasizing the essential need for sustainable development routes with lower greenhouse gas emissions. This finding has important implications for forecasting fire activity across NEC and advancing the global environmental projection. Key Points The escalation of fire in Northeast China during the past decade is strongly linked with the decline of Bering Sea ice concentration Weakened vertical wind shear, the high‐pressure center and northerly winds induced by warmer Bering Sea might explain the teleconnection This linkage could potentially be intensified in a warmer world

Two synoptic wind‐driven situations of the circulation in the northern Adriatic were studied using the Princeton Ocean Model over the northern Adriatic Sea (NAPOM). In both situations the basin was driven by a relatively steady wind (>8 m/s) along and across the basin over three days. In the first situation (28–30 October 2008) the SSE southern jugo or scirocco wind blew along the basin, and in the second (19–21 March 2009), the ENE bora wind blew across the basin. Cyclonic turn was present in the first situation, while the cyclonic branch of a known double‐gyre circulation north of the strip of wind minima was evident in the second. We show that during the jugo the model does not confirm quantitatively the simple topographic control of a wind‐driven circulation, suitable for elongated basins, while qualitatively the model meets expectations, with downwind transport in shallow areas close to shorelines and upwind transport in places with greater depths. During the bora wind, however, the wind‐driven circulation in the Gulf of Trieste is well explained by this topographic control (82% of the flux through the transect). Key Points New simple method for the evaluation of topography control The Gulf of Trieste has topography control of the wind‐driven circulation Numerical model applied for the validation of topography control

Plastics have been found in several compartments in Antarctica. However, there is currently no evidence of their presence on Antarctic glaciers. Our pilot study investigated plastic occurrence on two ice surfaces (one area around Uruguay Lake and another one around Ionosferico Lake) that constitute part of the ablation zone of Collins Glacier (King George Island, Antarctica). Our results showed that expanded polystyrene (EPS) was ubiquitous, ranging from 0.17 to 0.33 items m−2, whereas polyester was found only on the ice surface around Uruguay Lake (0.25 items m−2). Furthermore, we evaluated the daily changes in the presence of plastics in these areas in the absence of rainfall to clarify the role of the wind in their transport. We registered an atmospheric dry deposition rate between 0.08 items m−2 d−1 on the ice surface around Uruguay Lake and 0.17 items m−2 d−1 on the ice surface around Ionosferico Lake. Our pilot study is the first report of plastic pollution presence on an Antarctic glacier, possibly originated from local current and past activities and likely deposited by wind transport.

Despite frequent foehns in the Beijing–Tianjin–Hebei (BTH) region, there are only a few studies of their effects on air pollution in this region, or elsewhere. Here, we discuss a foehn-induced haze front (HF) event using observational data to document its structure and evolution. Using a dense network of comprehensive measurements in the BTH region, our analyses indicate that the foehn played an important role in the formation of the HF with significant impacts on air pollution. Northerly warm–dry foehn winds, with low particulate concentration in the northern area, collided with a cold–wet polluted air mass to the south and formed an HF in the urban area. The HF, which is associated with a surface wind convergence line and distinct contrasts of temperature, humidity and pollutant concentrations, resulted in an explosive growth of particulate concentration. As the plain–mountain wind circulation was overpowered by the foehn, a weak pressure gradient due to the different air densities between air masses was the main factor forcing advances of the polluted air mass into the clean air mass, resulting in severe air pollution over the main urban areas. Our results show that the foehn can affect air pollution through two effects: direct wind transport of air pollutants, and altering the air mass properties to inhibit boundary layer growth and thus indirectly aggravating air pollution. This study highlights the need to further investigate the foehn and its impacts on air pollution in the BTH region.

This work aims to clarify the relation between the Atlantic meridional overturning circulation (AMOC) and the thermal wind. We derive a new and generic dynamical AMOC decomposition that expresses the thermal wind transport as a simple vertical integral function of eastern minus western boundary densities. This allows us to express density anomalies at any depth as a geostrophic transport in Sverdrups (1 Sv ≡ 10 6 m 3 s −1 ) per meter and to predict that density anomalies around the depth of maximum overturning induce most AMOC transport. We then apply this formalism to identify the dynamical drivers of the centennial AMOC variability in the CNRM-CM6 climate model. The dynamical reconstruction and specifically the thermal wind component explain over 80% of the low-frequency AMOC variance at all latitudes, which is therefore almost exclusively driven by density anomalies at both zonal boundaries. This transport variability is dominated by density anomalies between depths of 500 and 1500 m, in agreement with theoretical predictions. At those depths, southward-propagating western boundary temperature anomalies induce the centennial geostrophic AMOC transport variability in the North Atlantic. They are originated along the western boundary of the subpolar gyre through the Labrador Sea deep convection and the Davis Strait overflow.

From 23 January to 13 February 2020, 20 ATR-42 scientific flights were conducted in the framework of the EUREC4A field campaign over the tropical Atlantic, off the coast of Barbados (13∘30′ N, -58∘30′ W). By means of a sideway-pointing lidar, these flights allowed us to retrieve the optical properties of the aerosols found in the sub-cloud layer and below the trade wind inversion. Two distinct periods with significant aerosol contents were identified in relationship with the so-called trade wind and tropical regimes, respectively. For these two regimes, mixings of two air mass types encompassing dust and carbonaceous aerosols have been highlighted. Both were mainly from West Africa with similar optical contributions and linked to dust uptake above Sahara and biomass burning between Guinea-Bissau and Côte d'Ivoire. In the tropical transport regime, the wind within the planetary boundary layer is stronger and favours a contribution of marine aerosols (sulfate and sea salt aerosol components) in shallower aerosol layers than for the trade wind transport regime. The latter is responsible for advecting dust–biomass-burning-aerosol mixtures in the deeper, well-mixed layer, in part due to the complex interactions of the easterly flow from West Africa with mid-latitude dynamics. The aerosol vertical structures appear to be well reproduced using atmospheric composition reanalyses from CAMS when comparing with lidar-derived vertical profiles. The competition between the two types of transport regimes leads to strong heterogeneity in the optical properties of the horizontal aerosol field. Our study highlights the transport regime under which a significant mixture of dust and biomass burning aerosols from West Africa can be observed over the Caribbean and Barbados in particular, namely the trade wind regime.

This study presents the first detailed analysis of a Late Pleistocene cliff-front dune in northern Mallorca (Western Mediterranean). The research is based on sedimentological fieldwork conducted in a disused coastal quarry, where stratigraphic columns were recorded and facies were described in detail. Grain size analysis was performed using image-based measurements from representative samples, and palaeowind conditions were reconstructed through the analysis of cross-bedding orientations and empirical wind transport equations. The dune, corresponding to Unit U4, exhibits three distinct evolutionary stages: initial, intermediate, and final. During the initial stage, sediment mobilisation required wind speeds of approximately 10 m/s from the south-southwest (SSW). The intermediate stage was characterised by variable wind velocities between 5 and 8 m/s from the west-southwest (WSW). In the final stage, average wind speeds reached 7 m/s from the west (W), with intermittent peaks up to 10 m/s. These findings underscore the critical influence of wind regime and topographic constraints on aeolian sedimentation processes. By reconstructing wind dynamics and analysing sedimentary architecture, this work provides key insights into the interplay between climatic drivers and geological context in the development of coastal aeolian systems.

Urban areas and industrial facilities, which concentrate the majority of human activity and industrial production, are major sources of air pollutants, with serious implications for human health and global climate. For most of these pollutants, emission inventories are often highly uncertain, especially in developing countries. Spaceborne measurements from the TROPOMI instrument, on board the Sentinel-5 Precursor satellite, are used to retrieve nitrogen dioxide (NO2) column densities at high spatial resolution. Here, we use 2 years of TROPOMI retrievals to map nitrogen oxide (NOx = NO + NO2) emissions in Egypt with a top-down approach using the continuity equation in steady state. Emissions are expressed as the sum of a transport term and a sink term representing the three-body reaction comprising NO2 and hydroxyl radical (OH). This sink term requires information on the lifetime of NO2, which is calculated with the use of the CAMS near-real-time temperature and OH concentration fields. We compare this derived lifetime with the lifetime inferred from the fitting of NO2 line density profiles in large plumes with an exponentially modified Gaussian function. This comparison, which is conducted for different samples of NO2 patterns above the city of Riyadh, provides information on the reliability of the CAMS near-real-time OH concentration fields; it also provides some hint on the vertical levels that best represent typical pollution sources in industrial areas and megacities in the Middle East region. In Egypt, total emissions of NOx are dominated by the sink term, but they can be locally dominated by wind transport, especially along the Nile where human activities are concentrated. Megacities and industrial regions clearly appear as the largest sources of NOx emissions in the country. Our top-down model infers emissions with a marked annual variability. By looking at the spatial distribution of emissions at the scale of different cities with different industrial characteristics, it appears that this variability is consistent with national electricity consumption. We detect lower emissions on Fridays, which are inherent to the social norm of the country, and quantify the drop in emissions in 2020 due to the COVID-19 pandemic. Overall, our estimations of NOx emissions for Egypt are 7.0 % higher than the CAMS-GLOB-ANT_v4.2 inventory and significantly differ in terms of seasonality.

The melt of seasonal snowpack in mountain regions provides downstream river basins with a critical supply of freshwater. Snowdrift‐permitting models have been proposed as a way to accurately simulate snowpack heterogeneity that stems from differences in energy inputs, over winter redistribution, sublimation, melt, and variations in precipitation. However, these spatial scales can be computationally intractable for large extents. In this work, the multiscale Canadian Hydrological Model (CHM) was applied to simulate snowpacks at snowdrift‐permitting scales (≈50 m) across the Canadian Cordillera and adjacent regions (1.37 million km2) forced by downscaled atmospheric data. The use of a multiscale land surface representation resulted in a reduction of computational elements of 98% while preserving land‐surface heterogeneity. CHM includes complex terrain windflow and radiative transfer calculations, lapses temperature, humidity, and precipitation with elevation, redistributes snow by avalanching, wind transport and forest canopy interception and calculates the energetics of canopy and surface snowpacks. Model outputs were compared to a set of multiscale observations including snow‐covered area (SCA) from Sentinel and Landsat imagery, snow depth from uncrewed aerial system lidar, and point surface observations of depth and density. Including snow redistribution and sublimation processes improved the summer SCA r2 from 0.7 to 0.9. At larger scales, inclusion of snow redistribution processes delayed full snowpack ablation by an average of 33 days, demonstrating process emergence with scale. These simulations show how multiscale modeling can improve snowpack predictions to support prediction of water supply, droughts, and floods. Plain Language Summary The spring melting of snowpacks in mountainous regions is crucial for providing freshwater to downstream river basins. Accurate simulation of mountain snowpacks requires accounting for factors like energy input, redistribution of snow, and forest canopies. However, including all these factors can be computationally challenging for large areas. In this study, the Canadian Hydrological Model (CHM) was used to simulate snowpacks at fine scales (about 50 m) across the Canadian Cordillera and nearby regions. By using a multiscale approach, the computational requirements were reduced substantially while maintaining the range of landscape features. The CHM accounts for various factors such as windflow, mountain shadowing, temperature, humidity, and precipitation changes with elevation, as well as snow redistribution through avalanching and wind transport. The model was validated against multiscale observations including satellite imagery, lidar data, and point observations. By incorporating snow redistribution and sublimation processes in the model, the accuracy of snow cover predictions improved over spring and summer. At larger scales, considering snow redistribution delayed the complete melting of snowpacks by an average of 33 days, showcasing the importance of scale‐dependent redistribution and ablation processes. These simulations demonstrate how multiscale modeling enhances snowpack predictions, aiding in forecasts of water supply, droughts, and floods. Key Points A novel, large extent, snowdrift permitting scale simulation of ≈1.4 M km2 was performed The inclusion of snow redistribution was scale emergent and delayed full snowcover ablation by 33 days on average The inclusion of snow redistribution processes improved the summer simulated versus observed snow‐covered area r2 from 0.7 to 0.9

Meteorological connectivity between biological hot spots of the McMurdo Dry Valleys (MDVs) of Antarctica is thought to play a role in species distribution and abundance through the aeolian transport of bioaerosols. Understanding the potential role of such meteorological connectivity requires an understanding of near-surface wind flow within and between valley airsheds. To address this, we applied Lagrangian wind trajectory modeling to mesoscale (spatial resolution of ∼1 km) weather model output to predict connectivity pathways, focusing on regions of high biodiversity. Our models produce maps of a likelihood metric of wind connectivity that demonstrate the synoptic and mesoscale dependence of connections between local, near-local, and nonlocal areas on wind transport, modulated by synoptic weather and topographic forcing. These connectivity areas can have spatial trends modulated by the synoptic weather patterns and locally induced topographically forced winds. This method is transferrable to other regions of Antarctica for broader terrestrial, coastal, and offshore ecological connectivity research. Also, our analysis and methods can inform better placement of aeolian dust and bioaerosol samplers in the McMurdo Dry Valleys, provide preliminary guidelines behind the meteorological controls of sediment transport and smaller particle distribution, and present quantifiable knowledge informing new hypotheses around the potential of wind acting as a physical driver for biological connectivity in the MDVs.