Search Results (256)

This study explores the three-dimensional structure of dust aerosols over the Qaidam Basin using CALIPSO satellite observations from 2007 to 2022. The results show that polluted dust is the dominant aerosol type in this region. Dust activity peaks in spring, with its vertical extent reaching nearly 10 km. Dust Aerosol Optical Depth (DAOD) is relatively high in the northwest and central parts of the basin, with a spring peak of 0.25 and an autumn minimum of 0.12. DAOD has shown a notable decreasing trend over the past 16 years. In terms of vertical structure, dust aerosols are mainly concentrated below 4 km AGL, especially within the near-surface layer of 0–2 km, and their occurrence frequency declines as altitude increases. The dust layer thickness exhibits obvious seasonal variations, which are primarily controlled by changes in layer top height. The average thickness decreases from 1.53 km in spring to 0.61 km in winter, while the layer’s bottom height remains fairly stable. Analysis based on the LASSO-SHAP model indicates that potential evapotranspiration and friction velocity are the major factors affecting DAOD, highlighting the vital roles of surface dryness and near-surface dynamic forcing. Furthermore, investigation of typical dust events reveals distinct vertical stratification of dust transport. Low-level dust movement is restricted by basin terrain, whereas upper levels are governed by the westerlies. This study improves our understanding of the three-dimensional structure, seasonal evolution, and transport processes of dust aerosols in high-altitude arid basins. Full article

Greece and the eastern Mediterranean are among the regions that are most exposed to climate-driven natural hazards, with wildfires, floods, and extreme rainfall events consistently producing significant socioeconomic and environmental impacts. Although previous literature has addressed each hazard type individually, a systematic, comparative analysis of the atmospheric circulation regimes associated with all three hazard categories within a unified Lagrangian framework has not yet been conducted for Greece. In this study, a 96 h HYSPLIT back-trajectory analysis driven by ERA5 reanalysis data, combined with k-means clustering, is employed to characterise the air mass origins associated with extreme events in Greece from 2000 to 2020 at two atmospheric levels: 750 m and 3000 m above sea level. Wildfire events are predominantly linked to short-distance northeast airflow at 750 m, and are directly associated with the Etesian wind system and to a coherent northwest-west Mediterranean signal at 3000 m, reflecting the influence of the summer blocking anticyclone over Europe. Conversely, flood events are dominated by northerly flow at 750 m, driven by the eastern flank of Mediterranean depressions. These results indicate that flooding in Greece is primarily conditioned by surface cyclogenesis, regardless of the upper-level flow geometry. Extreme rainfall events exhibit the most complex structure, with a dominant upper-level cluster that describes a recurving trajectory consistent with cut-off low dynamics. Cross-hazard comparisons demonstrate that similar near-surface trajectory patterns may arise from different atmospheric drivers, underscoring the necessity of integrating Lagrangian trajectory classification with additional context, such as thermodynamic and seasonal, to enable robust multi-hazard attribution and enhance early warning capabilities in the eastern Mediterranean. Full article

As a core and priority region of the Beijing-Tianjin Sandstorm Source Control Project, the mountainous area of northern Hebei plays a critical role in restraining desertification and ensuring the ecological security and sustainable development of the capital region. To reveal the ecosystem service flow mechanism of windbreak and sand fixation and support regional ecological sustainability, this study first used the Revised Wind Erosion Equation (RWEQ) to evaluate the spatial distribution of windbreak and sand-fixation services in northern Hebei mountainous area. Then, the HYSPLIT model was applied to simulate the spatial flow paths, identify the radiation scope, and quantify the radiation intensity of these ecosystem services. The results reflect the modeled patterns under given assumptions rather than fully verified actual ecosystem service supply. In 2024, the total amount of windbreak and sand-fixation service in the study area reached 10.3553 × 10⁶ tons. Sand-dust weather mainly occurred in spring and autumn, accounting for 39.23% and 33.46% of the total, respectively. The spatial flow paths were dominated by the northwest pathway (43.01%) and west pathway (38.17%). The total radiation scope of windbreak and sand-fixation services was 396.16 × 10⁴ km², among which 342.96 × 10⁴ km² was within the study area, accounting for 86.57%. The average service density was 21.06 kg/hm². The service density along flow paths decreased with increasing transport distance, while the radiation scope expanded with the increase in trajectory frequency. Spatially, the sand-fixation material density showed a circular decreasing trend from the center to the periphery of the study area. This study clarifies the flow characteristics and radiation benefits of windbreak and sand-fixation ecosystem services, which can provide a scientific basis for regional ecological protection, ecosystem service management, and the promotion of regional ecological sustainability. Full article

Climate change amplifies urban sustainability challenges, with intensifying sand and dust storm (SDS) hazards highlighting the important role of Ecosystem wind erosion prevention (EWEP) as an ecosystem service (ES). In northern China, a region prone to wind erosion, EWEP mitigates aeolian processes at sand sources and reduces downwind dust transport to urban centers. This study employs the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model to simulate diffusion dynamics of EWEP and to assess its hazard mitigation effects for cities in northern China. The findings are as follows: (1) EWEP capacity increased consistently from 2000 to 2024; (2) Aggregated preventive benefits rose, which aligns with the interpretation that systemic ecological restoration reduces dust dispersion; (3) Preventive benefits exhibit stratification across different urban agglomerations. These findings can inform SDS risk management and climate adaptation strategies to support urban sustainability. Full article

This study assessed photovoltaic (PV) soiling losses at Alamogordo, New Mexico, USA, located within the Chihuahuan Desert and near the White Sands gypsum dune field, a region with frequent dust events. Soiling material collected from PV module surfaces showed seasonal variations in mineral composition, with quartz being the main component during the fall season and calcite predominating during the spring. All samples collected during the following spring season contained large amounts of gypsum, indicating transport from White Sands, supported by HYSPLIT back-trajectories and surface wind data. Soiling materials collected from PV module surfaces generally had a mineral composition similar to that of the surrounding local soils. The mean particle size of collected soiling material samples ranged from 8 to 21 µm, with ~90% of particles being dust (<50 µm) and ~10% of the soiling particles being sand (>50 µm). Despite Alamogordo experiencing 22 dust events during this study, soiling-related power losses were relatively low, about 2% to 3%, much lower than reported for Global Dust Belt locations. The prevailing south-to-southwest winds and their gusts acted as a passive cleaning mechanism, as they were aligned with the front of the PV modules and likely resuspended particles off panel surfaces. Additionally, relatively low rainfall (about 2.2 mm per hour) was effective in restoring PV performance. These findings suggest that, due to the relatively low soiling losses observed, frequent cleaning may not be necessary at this location, resulting in potential savings in maintenance costs over the long-term operation of the PV system. Full article

Against the background of a warming and humidifying climate on the Qinghai–Tibet Plateau, increasing attention has been paid to the sustainability of water resources and ecosystems in the Qinghai Lake Basin. Investigating the characteristics of precipitation stable isotopes and moisture sources provides critical insights into the driving mechanisms of the regional hydrological cycle. In this study, precipitation samples collected at the Qinghai Lake Wetland Ecosystem National Observation and Research Station from June 2023 to October 2024 were analyzed for hydrogen (δ²H) and oxygen (δ¹⁸O) stable isotopes. The temporal variations of δ²H, δ¹⁸O, and deuterium excess (d-excess) were characterized, and their relationships with air temperature and precipitation amount were examined. In addition, a backward trajectory model was employed to identify the moisture sources of precipitation during the observation period. The results indicate that: (1) precipitation stable isotopes and d-excess exhibit pronounced seasonal variability, characterized by enrichment in summer and depletion in spring and autumn; (2) the Local Meteoric Water Line (LMWL) for the basin is defined as δ²H = 8.15δ¹⁸O + 38.71 (R² = 0.93), with both slope and intercept exceeding those of the Global Meteoric Water Line (GMWL); (3) precipitation isotopes show a discernible temperature effect but are jointly controlled by multiple moisture sources and meteorological factors; and (4) backward trajectory analysis combined with d-excess values reveals that precipitation moisture is primarily derived from westerly transport, while locally recycled moisture and continental air masses also exert significant influences. Overall, these findings reveal the multi-source driving mechanisms of the regional hydrological cycle and provide critical scientific support for understanding hydrological processes in alpine inland basins and their responses to future climate change, thereby contributing to the sustainable management of regional water resources. Full article

Atmospheric aerosols in Southeast Asia, influenced by climate and seasonal circulation, are examined here. This study analyzes the impact of the 2015 El Niño and monsoonal variability on aerosol properties over Penang, Malaysia, from 2015–2019. Aerosol Optical Depth (AOD), Ångström Exponent (AE), Fine Mode Fraction (FMF), and Single Scattering Albedo (SSA) were analyzed using AERONET observations, complemented by satellite-derived fire data and NOAA HYSPLIT back-trajectory analysis. Pronounced seasonal variability was observed, with elevated AOD during the Southwest Monsoon (0.72 ± 0.15) associated with biomass burning and mixed urban aerosols, and lower AOD during the Northeast Monsoon (0.47 ± 0.12) due to cleaner maritime air masses. The inter-monsoon period exhibited the lowest AOD (0.28 ± 0.10), reflecting enhanced wet scavenging and mixed aerosol sources. Interannually, the 2015 El Niño recorded substantially higher aerosol loading, including extreme AOD events (>1.75), driven by intensified regional fire activity under dry conditions. A statistically significant but weak correlation (R² = 0.12, p = 0.047) indicates biomass burning contributed to AOD, though transport processes were the dominant driver. Trajectory analysis confirmed that aerosols originated from fire-affected Sumatra during the Southwest Monsoon and from the South China Sea during the Northeast Monsoon. These results show that climate and winds drive aerosol changes, so regional monitoring and cross-border air management in Southeast Asia are needed. Full article

In the Yingjiang area of western Yunnan, precipitation is high throughout the year, making it one of the regions with the highest annual precipitation in mainland China. Extreme rainfall in this region often triggers severe flooding, yet the key mechanism of water vapor transport underlying abnormally heavy precipitation remains unclear. This study used automatic weather station observations of precipitation, the fifth-generation atmospheric reanalysis produced by the European Centre for Medium-Range Weather Forecasts, and Global Data Assimilation System (GDAS) data to analyze, for the first time, large-scale water vapor transport, precipitation mechanisms, and the primary water vapor sources and their contributions in this region. The results show the following: In the Yingjiang area, the water vapor sources at all height levels in summer are dominated by the southwest monsoon water vapor transport pathways, such as the Bay of Bengal and the Arabian Sea, with their total contributions to specific humidity and water vapor flux exceeding 70%. This indicates that low-latitude sea areas such as the Bay of Bengal and the Arabian Sea serve as key moisture source regions for Yingjiang in the global water vapor cycle. Water vapor transport over the windward slope causes strong low-level convergence and high-level divergence phenomena, and the suction effect leads to strong upward motion near the 850 hPa level. The pseudo-equivalent potential temperature isolines tilt along the mountain slope, maintaining an unstable stratification characterized by warm, humid lower layers and cold, dry upper layers, providing favorable thermal conditions for precipitation. In addition, in the summer of 2020, abnormally high southwest seasonal wind and air transport, combined with strong low-level convergence and high-level divergence of the vertical circulation structure, were key factors causing the abnormally high precipitation. This study provides an important reference for the prediction of extreme precipitation and the early warning of rainstorm disasters in the southwest monsoon region in the context of global climate change. Full article

Clarifying migration pathways and the source area–destination relationships of the domestic and foreign beet webworm Loxostege sticticalis (Linnaeus) populations, as well as understanding the meteorological mechanisms shaping these processes, is pivotal for remote, accurate, and location-specific pest early warning and forecasting. Based on light trap data from northern China and field survey data from Mongolia in 2022, we simulated the migration trajectories, source regions, and primary landing areas of L. sticticalis by using the HYSPLIT model and analyzed the synoptic systems, processes and conditions during its migration. The results indicate the frequent exchange of L. sticticalis populations between China and Mongolia in 2022. The L. sticticalis migrants initiating their flights from Mongolia primarily undertook a southeastward migration pathway, supplemented by eastward ‘cyclonic’ and southwestward paths. The main landing areas were located in North China and Northeast China, with migration events potentially extending to the Shandong, Heilongjiang, and Xinjiang provinces. Populations originating from North China exhibited a capacity for migrating into Northeast China and Mongolia through 1–5 consecutive nights of flight. During this period, the Northeast China Cold Vortex (NCCV) and the Mongolian Cyclone alternately regulated the synoptic circulation pattern governing the migration of L. sticticalis. The spatiotemporal distributions and intensities of these systems were key determinants of the transboundary migration routes and distances of L. sticticalis. The NCCV dominated, and the precipitation and downdrafts it induced were crucial for the massive landing of L. sticticalis in northern China. Full article

We present an improved algorithm based on the POlarization LIdar PHOtometer Networking (POLIPHON) method to retrieve cloud condensation nuclei (CCN) concentration profiles from spaceborne lidar observations. Our previous paper, which was the first study to demonstrate the feasibility of using measurements from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) to retrieve CCN is revisited. Our results focus on the Evaluation of CALIPSO’s Aerosol Classification scheme over Eastern Mediterranean (ACEMED) research campaign that took place over Thessaloniki, Greece, in September 2011. We compare our results with our earlier retrievals, discussing the critical changes that have been made and the importance of using the proper conversions factors. We also demonstrate the use of conversion factors acquired based on CALIPSO aerosol typing for CCN retrievals. The analysis highlights the strong influence of smoke on CCN concentrations and shows that the assumed aging state of the smoke can significantly alter the retrieval outcome. Full article

Marine aerosol particles influence the climate, and interactions between ocean waves and coral reefs may impact aerosol size distributions in remote locations, such as the Great Barrier Reef. However, quantifying these processes has proven to be challenging. We tested whether marine aerosol size distributions and concentrations differ across four zones: background air outside the lagoon, above the reef crest, within the lagoon, and near the beach of Heron Island, approximately 85 km offshore. Using a modified DJI Matrice 600 hexacopter equipped with a miniaturised optical particle counter and custom inline gas dryer, we measured aerosols from 165 to 3000 nm across 64 drone flights during 16 sampling events in November 2024. Aerosol concentrations showed substantial day-to-day temporal variability, while spatial differences among reef zones were generally minor; on certain days, the maximum difference between background and near-island measurements reached approximately 25%. K-means clustering identified four dominant air mass transport patterns, and Hybrid Single-Particle Lagrangian Integrated Trajectory model analysis indicated that upwind conditions had a strong influence on aerosol loading. Vertical profiles revealed limited variability within the lowest 100 m. Mixing layer height, air parcel travel speed, and water depth along the final 12 h of trajectories were key drivers of aerosol variability. These results demonstrate the potential of drone-based measurements for characterising marine aerosols and provide a foundation for improving climate model representations of natural aerosol processes. Full article

Southwestern China serves as a critical region for carbon sources and sinks, influenced by both natural ecosystems and anthropogenic activities. The Shangri-La atmospheric background station (28.01° N, 99.73° E), the only regional station in southwestern China, provides essential data for understanding CO₂ dynamics. This study analyzes hourly CO₂ mole fractions from 2019 to 2022. Background signals were extracted using the Robust Extraction of Baseline Signal (REBS) algorithm, and air-mass trajectories were analyzed using HYSPLIT model and Potential Source Contribution Function (PSCF) and Concentration Weighted Trajectory (CWT) methods. The REBS-derived background CO₂ concentration increased from ~409 ppm in 2019 to ~417 ppm in 2022, yielding a growth rate of 1.9 ± 0.1 ppm yr⁻¹, slightly lower than the 2010–2014 rate reported previously and consistent with the recent global slowdown associated with ENSO-driven carbon–climate variability. A coherent seasonal cycle, with spring maxima and late-summer minima, reflects the combined influence of biospheric uptake and monsoonal inflow. Comparison with the global marine boundary layer and Waliguan records shows similar phase and amplitude, confirming the representativeness of Shangri-La as a regional background site, albeit with a one-month phase lag to Waliguan station due to regional climatic and phenological differences. Trajectory and wind analyses identify southern Indo-Myanmar and Sichuan–Yunnan regions as major transport corridors influencing high-CO₂ events. Overall, the results highlight that regional transport rather than local emissions dominates CO₂ variability at Shangri-La. The derived background and transport signals thus provide an updated and internally consistent characterization of carbon-cycle variability over the southeastern Tibetan Plateau, offering critical observational support for future regional carbon budget assessments. Full article

The Tibetan Plateau (TP), known as the “Asian Water Tower,” plays a critical role in regional and global climate systems. However, water resource sustainability is increasingly threatened under climate change and growing demand. While moisture transport mechanisms for summer monsoon and extreme precipitation events have been widely studied, the understanding of moisture sources for different precipitation intensities remains limited. This study employs the Lagrangian-based HYSPLIT model to quantify moisture source contributions to three types of precipitation events—extreme precipitation (EP), moderate precipitation (MP), and light precipitation (LP)—over the TP from 1979 to 2020. Using trajectory clustering and moisture source diagnostics, we identify dominant transport pathways and their relative contributions. Results show that EP and MP events are primarily influenced by the Indian monsoon, with the Bay of Bengal and Arabian Sea as key sources, while LP events are dominated by westerlies. The western pathway contributes 15.55%, 36.28%, and 59.59% to EP, MP, and LP events, respectively, whereas the monsoon pathway accounts for 40.56%, 28.23%, and 31.21%. External moisture sources dominate across all event types (average 87.7%), with local recycling contributions decreasing from LP (12.90%) to EP (11.55%). These findings enhance the understanding of moisture–precipitation coupling mechanisms over the TP and provide a scientific basis for water resource management under changing climate conditions. Full article

Atmospheric fine particles (PM_2.5, aerodynamic diameter ≤ 2.5 µm) have a serious effect on human health. This study combined concentration weighted trajectory (CWT) analysis with the HYSPLIT trajectory ensemble (Ens-HYSPLIT-CWT), to separate the sources of PM_2.5 transported to Beijing, and further investigate the effect of PM_2.5 originated from different sources on human health. We found that north region air masses usually come with clean events under the blessing of meteorological conditions, combined with the clean air mass transported from the north, as high wind speed near the surface promotes the horizontal diffusion of pollutants. Additionally, north region air masses contribute to the decrease in aerosol optical depth (AOD) at Beijing and surrounding areas, with AF (daily attributable fraction associated with short-term PM_2.5 exposure) values of Beijing only at 0.14. During the study period (from January to March 2024), south region air masses usually come with high PM_2.5 values, which is correlated to the meteorological conditions and pollutant spatial distribution. The air masses coming from the south region contain high temperature and relative humidity (RH), promoting the occurrence of high pollution events. AOD spatial distribution observed from satellites showed that except for the dominance of north region air mass sources, the south region presents high AOD values, further resulting in the highest AF value of 0.75 obtained at Beijing, which is 5 times higher than the north region’s dominant AF mean value. It is worth noting that the air mass originated from the east region, which originally contributed relatively clean air masses before emission reduction, increased its contribution to air mass pollution after emission reduction due to the decrease in pollution concentration in other regions. As a result, the mean PM_2.5 in this source area was second only to south region air masses and local emission sources, and the AF value even exceeded local emissions, second only to south region air mass sources, reaching 0.5. This result emphasizes that in future pollution control policy adjustments and research on human health, attention needs to be paid to the contribution of eastward air masses. Full article

Heavy snowfall events in the Ural region have drawn significant attention due to their substantial frequency, the region’s relatively high population density and its developed network of roads and power lines. This study summarizes the main characteristics of the hazardous heavy snowfall (HHS) events (≥20 mm 12 h⁻¹) that have occurred in the Ural region between 1981 and 2025, as well as in related synoptic-scale environments, for the first time. The dataset consists of 116 HHS reports, with 12-hourly snowfall intensities ranging from 20 mm to 47.6 mm. The main characteristics of these events (snowfall amount, spatial distribution, inter-annual and seasonal variability and trends, associated weather phenomena, and related damage) are examined based on the data from weather stations, the ERA5 reanalysis, scientific literature, and media reports. While there is no statistically significant trend in HHS events, the frequency of the most damaging late spring and early autumn snowfalls has decreased. Using 72 h backward trajectories according to the NOAA HYSPLIT model and the ERA5 reanalysis, we classified the HHS events into five types according to air mass origin, and performed a composite analysis for each type. The main finding is that 46% of HHS reports are related to cyclones forming over the Caspian and Aral seas, resulting in a higher frequency of HHS events to the east of the Ural Mountains compared to the western part of the region. Full article