Tian Zhou

The long-range eastward transport of North African dust substantially influences China's climate, environment, and human health. However, the circulation mechanisms that modulate its pathway variability and downstream impacts remain poorly understood. In this study, we investigated the synoptic patterns along three distinct eastward transport pathways of North African dust and their impacts on air quality in China using reanalysis and observations. Results show that seasonal variations in dust activity and the position of the westerly belt govern the eastward transport of North African dust, with transport peaking in April and spring accounting for 56.3 % of the annual dust mass potentially available for eastward transport. Among the three transport pathways, the northern pathway transports dust northward into Europe, followed by eastward advection through the mid- and high-latitude westerlies following pre-trough uplift. In contrast, the middle pathway features Mediterranean uplift and northeastward deflection. Mid-latitude westerly transport is modulated by western Mediterranean cyclonic activity, a southward-extending trough, and the blocking and splitting effects of the European high-pressure system. The southern pathway transports dust eastward along lower latitudes and around the southern Tibetan Plateau toward southern China. This pathway is guided by southward displaced lower-latitude westerlies, the European cold trough, and Himalayan topographic deflection. These dust plumes produce maximum PM_2.5 anomalies of 54.1–202.4 μgm^-3 decreasing from north to south across China. These findings may support early warnings of the eastward transport of North African dust to East Asia—an overlooked issue that is becoming increasingly critical as aerosol levels decline in China.

The long-range eastward transport of North African dust substantially influences China's climate, environment, and human health. However, the circulation mechanisms that modulate its pathway variability and downstream impacts remain poorly understood. In this study, we investigated the synoptic patterns along three distinct eastward transport pathways of North African dust and their impacts on air quality in China using reanalysis and observations. Results show that seasonal variations in dust activity and the position of the westerly belt govern the eastward transport of North African dust, with transport peaking in April and spring accounting for 56.3 % of the annual dust mass potentially available for eastward transport. Among the three transport pathways, the northern pathway transports dust northward into Europe, followed by eastward advection through the mid- and high-latitude westerlies following pre-trough uplift. In contrast, the middle pathway features Mediterranean uplift and northeastward deflection. Mid-latitude westerly transport is modulated by western Mediterranean cyclonic activity, a southward-extending trough, and the blocking and splitting effects of the European high-pressure system. The southern pathway transports dust eastward along lower latitudes and around the southern Tibetan Plateau toward southern China. This pathway is guided by southward displaced lower-latitude westerlies, the European cold trough, and Himalayan topographic deflection. These dust plumes produce maximum PM_2.5 anomalies of 54.1–202.4 μgm^-3 decreasing from north to south across China. These findings may support early warnings of the eastward transport of North African dust to East Asia—an overlooked issue that is becoming increasingly critical as aerosol levels decline in China.

The long-range eastward transport of North African dust substantially influences China's climate, environment, and human health. However, the circulation mechanisms that modulate its pathway variability and downstream impacts remain poorly understood. In this study, we investigated the synoptic patterns along three distinct eastward transport pathways of North African dust and their impacts on air quality in China using reanalysis and observations. Results show that seasonal variations in dust activity and the position of the westerly belt govern the eastward transport of North African dust, with transport peaking in April and spring accounting for 56.3 % of the annual dust mass potentially available for eastward transport. Among the three transport pathways, the northern pathway transports dust northward into Europe, followed by eastward advection through the mid- and high-latitude westerlies following pre-trough uplift. In contrast, the middle pathway features Mediterranean uplift and northeastward deflection. Mid-latitude westerly transport is modulated by western Mediterranean cyclonic activity, a southward-extending trough, and the blocking and splitting effects of the European high-pressure system. The southern pathway transports dust eastward along lower latitudes and around the southern Tibetan Plateau toward southern China. This pathway is guided by southward displaced lower-latitude westerlies, the European cold trough, and Himalayan topographic deflection. These dust plumes produce maximum PM2.5 anomalies of 54.1–202.4 μgm-3 decreasing from north to south across China. These findings may support early warnings of the eastward transport of North African dust to East Asia—an overlooked issue that is becoming increasingly critical as aerosol levels decline in China.

The cyclic processes of aerosol evolution have a profound impact on regional climate, water resources and ecosystems. However, studies on diurnal variations of aerosol vertical distribution in typical ecologically sensitive areas remain scarce due to limited availability of high-resolution profiles. This study first identifies the elevated aerosol layer (EAL) embedded within the daytime mixed layer over the Hexi Corridor, northwest China, defined as a high-concentration layer above the surface but within the mixed layer. Based on intensive observation campaigns conducted in 2010 and 2012, we analyze the diurnal variation, formation mechanisms, air quality and radiative effects of EALs. The results show that EALs frequently occur at altitudes of 0.6–2 km during daytime. Excluding dust events, the occurrence frequencies were 82 % and 44 % at Dunhuang and Minqin, respectively; the layers were more frequently dust-influenced at Dunhuang and fine-mode/anthropogenic-aerosol-influenced at Minqin. Driven by a thermodynamic coupling effect characterized by positive anomalies in potential temperature and negative anomalies in relative humidity, aerosols accumulate at the bottom of the stable stratification. Thus, a simplified conceptual model for prediction is proposed. The peak Extinction-derived PM ₁₀ -equivalent mass concentration within EAL (203.3 ± 106.6 µg m ⁻³ ) at ∼1.2 km is five times higher than that at surface (40.8 ± 30.4 µg m ⁻³ ). Furthermore, the EALs enhance the atmospheric shortwave heating rate (up to 0.7 K d ⁻¹ ), indicating a potential impact on regional snowmelt/glacier retreat. These findings suggest that the aerosol vertical evolution should receive greater consideration in air pollution prevention, ecosystem protection, water resource management, and wind/solar-energy utilization in ecologically sensitive areas, particularly over complex terrains, rather than focusing solely on surface air pollution.

The cyclic processes of aerosol evolution have a profound impact on regional climate, water resources and ecosystems. However, studies on diurnal variations of aerosol vertical distribution in typical ecologically sensitive areas remain scarce due to limited availability of high-resolution profiles. This study first identifies elevated aerosol layer (EAL) within daytime mixed layer over the Hexi Corridor, northwest China, defined as a high-concentration layer above surface but within mixed layer. Based on intensive observation campaigns conducted in 2010 and 2012, we analyze the diurnal variation, formation mechanisms, air quality and radiative effects of EALs. The results show EALs frequently occur at altitudes of 0.6–2km during daytime. Excluding dust storms, occurrence frequencies reaches 81% (37%) in Dunhuang (Minqin) region , dominated by dust aerosol (anthropogenic pollutants). Driven by a thermodynamic coupling effect characterized by positive anomalies in potential temperature and negative anomalies in relative humidity, aerosols accumulate at the bottom of the stable stratification. Thus, a simplified conceptual model for prediction is proposed. The peak PM10 concentration within EAL (203.3±106.6μg/m³) at ~1.2km is five times higher than that at surface (40.8±30.4μg/m³). Furthermore, EALs enhance the atmospheric shortwave heating rate (up to 0.7K/day), and form a daily-scale heating pump that may accelerate snowmelt/glacier retreat in the region. These findings suggest that aerosol vertical evolution should receive greater consideration in air pollution prevention, ecosystem protection, water resource management, and wind/solar energy utilization in ecologically sensitive areas-particularly over complex terrains-rather than focusing solely on surface air pollution.

The cyclic processes of aerosol evolution have a profound impact on regional climate, water resources and ecosystems. However, studies on diurnal variations of aerosol vertical distribution in typical ecologically sensitive areas remain scarce due to limited availability of high-resolution profiles. This study first identifies elevated aerosol layer (EAL) within daytime mixed layer over the Hexi Corridor, northwest China, defined as a high-concentration layer above surface but within mixed layer. Based on intensive observation campaigns conducted in 2010 and 2012, we analyze the diurnal variation, formation mechanisms, air quality and radiative effects of EALs. The results show EALs frequently occur at altitudes of 0.6–2km during daytime. Excluding dust storms, occurrence frequencies reaches 81% (37%) in Dunhuang (Minqin) region , dominated by dust aerosol (anthropogenic pollutants). Driven by a thermodynamic coupling effect characterized by positive anomalies in potential temperature and negative anomalies in relative humidity, aerosols accumulate at the bottom of the stable stratification. Thus, a simplified conceptual model for prediction is proposed. The peak PM10 concentration within EAL (203.3±106.6μg/m³) at ~1.2km is five times higher than that at surface (40.8±30.4μg/m³). Furthermore, EALs enhance the atmospheric shortwave heating rate (up to 0.7K/day), and form a daily-scale heating pump that may accelerate snowmelt/glacier retreat in the region. These findings suggest that aerosol vertical evolution should receive greater consideration in air pollution prevention, ecosystem protection, water resource management, and wind/solar energy utilization in ecologically sensitive areas-particularly over complex terrains-rather than focusing solely on surface air pollution.

The cyclic processes of aerosol evolution have a profound impact on regional climate, water resources and ecosystems. However, studies on diurnal variations of aerosol vertical distribution in typical ecologically sensitive areas remain scarce due to limited availability of high-resolution profiles. This study first identifies elevated aerosol layer (EAL) within daytime mixed layer over the Hexi Corridor, northwest China, defined as a high-concentration layer above surface but within mixed layer. Based on intensive observation campaigns conducted in 2010 and 2012, we analyze the diurnal variation, formation mechanisms, air quality and radiative effects of EALs. The results show EALs frequently occur at altitudes of 0.6–2km during daytime. Excluding dust storms, occurrence frequencies reaches 81% (37%) in Dunhuang (Minqin) region , dominated by dust aerosol (anthropogenic pollutants). Driven by a thermodynamic coupling effect characterized by positive anomalies in potential temperature and negative anomalies in relative humidity, aerosols accumulate at the bottom of the stable stratification. Thus, a simplified conceptual model for prediction is proposed. The peak PM10 concentration within EAL (203.3±106.6μg/m³) at ~1.2km is five times higher than that at surface (40.8±30.4μg/m³). Furthermore, EALs enhance the atmospheric shortwave heating rate (up to 0.7K/day), and form a daily-scale heating pump that may accelerate snowmelt/glacier retreat in the region. These findings suggest that aerosol vertical evolution should receive greater consideration in air pollution prevention, ecosystem protection, water resource management, and wind/solar energy utilization in ecologically sensitive areas-particularly over complex terrains-rather than focusing solely on surface air pollution.

The long-range transport of bioaerosols by dust events significantly impacts ecological and meteorological networks of the atmosphere, biosphere and anthroposphere. Bioaerosols not only cause significant public health risks, but also act as efficient ice nuclei for inducing cloud formation and precipitation in the hydrological cycle. To establish risk management for bioaerosol impacts on the Earth system, a large-scale investigation of bioaerosols must be performed under different environmental conditions. For this purpose, a Dust-Bioaerosol (DuBi) field campaign was conducted, to investigate the distribution of bioaerosols by collecting ~ 950 samples at 39 sites across East Asia from 2016 to 2021. Concentrations and community structures of bioaerosols were further analyzed using fluorescence microscopic observations and high-throughput DNA sequencing, and these factors were compared to environmental factors, such as PM10 and aridity. The results indicated that microbial concentrations at dryland sites were statistically higher than those at humid sites, while the microbe to total particle ratio was statistically lower in drylands than in humid regions. Microbial cells per microgram of PM10 decreased when PM10 increased. The proportion of airborne particles at each site did not vary substantially with season. The richness and diversity of airborne bacteria were significantly higher in drylands than in semiarid regions, while the community structures were stable among all sampling sites. The DuBi field campaign helps a better understanding of bioaerosol characteristics variations along dust transport pathway in East Asia and the changes of bioaerosols under the trend of climate warming, supporting the efforts to reduce public health risks.

Saharan dust accounts for about 50-60% of the total global dust and can affect regional climate, environment and ecosystems through direct and indirect effects. However, the long-range transport of Saharan dust to East Asia and the further specific effects on its weather and climate are still poorly understood. Using the satellite observations combined with the model simulations, the multiple reanalysis data and HYSPLIT trajectory analysis, we systematically study the long-range transport of Saharan dust to East Asia and further study the impact of Saharan dust on the direct radiative forcing, clouds and precipitation in East Asia. A quarter (24.3 ± 6.2%) of dust cases in East Asia were originated from the Sahara Desert. The long-range transported Saharan dust is usually located in the upper troposphere of East Asia. The total annual average amount of Saharan dust transported over East Asia is 33.05 ± 9.78 Tg/year. Saharan dust can be transported eastward throughout the year and contributes about 35.8% of the dust to the upper troposphere in northern China in spring, which is almost equivalent to the amount of dust lifted from the East Asian dust source. Furthermore, in terms of regional impact, Saharan dust has a cooling effect on the surface and the top of the atmosphere, and a heating effect on the atmosphere. During a rainfall event, Saharan dust reduces the cloud supercooled water path over the Taklimakan Desert by 13.3 g/m2 in 3 h, converting supercooled water clouds into ice clouds and increasing the cloud ice-water path. As a result, a large amount of dust that acts as ice nuclei induces rainfall in the hinterland of the Taklimakan Desert as high as 6.32 mm. This study provides a new perspective on the important role of Saharan dust over East Asia, contributes to a better understanding of its long-range transport properties over East Asia and the sources of dust aloft in East Asia, and elucidates the impact of long-range transported dust on regional direct radiative forcing, clouds, and precipitation to better assess the impact of dust on climate and environment.

Dust from North Africa and Middle East can be long-range transported to East Asia and affect regional climate and environment. In this study, the separated simulation of the updated WRF-Chem model are used to investigate the transport characteristics of North African and Middle East dust during a dust event captured by ground-based lidar in Dunhuang, China on 5~8 April, 2012. The results show that it taken 6~7 days for dust plume transport from North Africa to East Asia. During the transport, the maximum concentration of dust plume decreased obviously. The top and bottom height remained at the altitude of 4~8 km. The results enrich the research on the transport of dust from North Africa to East Asia.