The impact of structural variations in the atmospheric boundary layer (ABL) during the regional transport of air pollutants on its local pollution changes deserves attention. Based on multi-source ABL detection and numerical simulation of air pollutants over the Twain-Hu Basin (THB) during 4–6 January 2019, the mechanism of the rapid growth of atmospheric pollutant concentrations in Xianning by the synergistic effect of regional transport and ABL evolution is explored, and the main conclusions are obtained as follows. The vertically stratified atmosphere is noticeable at nighttime, and the heavy humidity of near-surface fog within the stable boundary layer (SBL) promoted the generation and cumulative growth of secondary PM_2.5 components during the pollution formation stage. The horizontal transport characteristics of atmospheric pollutant concentration peak were observed in the residual layer (RL) of 500–600 m. At the pollution maintenance stage, the convective boundary layer (CBL) developed during the daytime, and northerly wind transported high-concentration pollutants from the north to the THB. Under the combined action of horizontal transport and turbulent mixing, the high-concentration atmospheric pollutants in the mixing layer (ML) from the ground to the 500 m height were mixed uniformly and maintained accumulation growth. The next day, the strong vertical turbulent mixing caused the downward transport of high-concentration pollutants in the RL during nighttime due to the development of the CBL again, resulting in a doubling of near-surface pollutant concentration in a short time. With the development of ABL turbulence, local pollution dissipated rapidly without the continuous input of pollutants from external regions. This study emphasizes the importance of multi-scale processes impact on pollution variation, that is, regional transport of atmospheric pollutants at the CBL development stage for the rapid growth of PM_2.5 concentration in the ML.

In this paper on the analysis of the vertical distribution of different-diameter dust aerosols and the potential impacts on East Asia, the sensitivity simulation tests of dust aerosols during 2002–03 were conducted by changing the underlying surface on the Qinghai-Tibet Plateau in the global atmospheric circulation model Community Atmosphere Model (CAM) 3.1. The results show that dust aerosol particles in East Asia are mainly distributed in the diameters of 0.64–5.12 μm. The high concentrations of dust aerosols are centered on the surface in the source areas and gradually raised during the eastward transport across East Asia, reaching a height of 4 km at 120° E. The small dust particles with diameters less than 1.28 μm are transported higher and farther driven by the midlatitude westerlies. The Qinghai-Tibet Plateau desertification leads to increasing concentrations of dust aerosols in all size bins and raisesthe transport height of dust aerosols in East Asia. The long-range transport in the East Asian troposphere is dominated by dust aerosols particles of diameters 0.64–2.56 μm, as well as a large contribution of dust aerosols with diameters larger than 1.28 μm.

The influence of the underlying surface on the atmospheric environment over rivers and lakes is not fully understood. To improve our understanding, this study targeted the Twain-Hu Basin (THB) in central China, with a unique underlying surface comprising a dense “water network” over rivers and lakes. In this study, the Weather Research and Forecasting Model with Chemistry (WRF-Chem) was used to simulate the impact of this dense “water network” on a wintertime heavy PM_2.5 pollution event in the THB. On this basis, the regulating effects of density and area of the lake groups, with centralized big lakes (CBLs) and discrete small lakes (DSLs), on PM_2.5 concentrations over the underlying surface of the dense “water network” in the THB were clarified, and the relative contributions of thermal factors and water vapor factors in the atmospheric boundary layer to the variation of PM_2.5 concentrations were evaluated. The results show that the underlying surface of dense “water networks” in the THB generally decreases the PM_2.5 concentrations, but the influences of different lake-group types are not uniform in spatial distribution. The CBLs can reduce the PM_2.5 concentrations over the lake and its surroundings by 4.90–17.68% during the day and night. The ability of DSLs in reducing PM_2.5 pollution is relatively weak, with the reversed contribution between −5.63% and 1.56%. Thermal factors and water vapor–related factors are the key meteorological drivers affecting the variation of PM_2.5 concentrations over the underlying surface of dense “water networks”. The warming and humidification effects of such underlying surfaces contribute positively and negatively to the “purification” of air pollution, respectively. The relative contributions of thermal factors and water vapor–related factors are 52.48% and 43.91% for CBLs and 65.96% and 27.31% for DSLs, respectively. The “purification” effect of the underlying surface with a dense “water network” in the THB on regional air pollution highlights the importance of environmental protection of inland rivers and lakes in regional environmental governance. In further studies on the atmospheric environment, long-term studies are necessary, including fine measurements in terms of meteorology and the environment and more comprehensive simulations under different scenarios.

In 2020, when the novel coronavirus disease 2019 (COVID-19) broke out as a global pandemic, cities in Hubei Province first went into lockdown on 23 January and resumed work and production on 20 March. From February to March 2020, human activities in Hubei decreased significantly, with the average particulate matter smaller than 2.5 μm (PM_2.5) concentration standing at 40 μg/m³, which is 21% lower than the expected based on a linear fitting trend in thePM_2.5 concentration in Hubei. By using the empirical orthogonal function (EOF) method, this paper comparatively analyzes the spatial-temporal variations of Hubei’s PM_2.5 concentration anomaly in February and March 2020 and the same periods of 2016–2019. The results show that the daytime peak of the PM_2.5 daily variation in Hubei in a low-emission scenario during COVID-19 declined significantly, to which human activities contributed the most. However, during nighttime, the PM_2.5 peak became more prominent, and the meteorological conditions had a more noticeable effect on the PM_2.5 concentration. In addition, during COVID-19, there was a great drop in PM_2.5 pollution accumulated from local sources within the urban circle of Wuhan City, while an increase was seen in central-western Hubei due to the inter-regional pollutant transport. Thus, the high PM_2.5 concentration center in the urban circle of Wuhan disappeared, but the pollution transport channel cities in central-western Hubei remained as high-PM_2.5-concentration centers.

This study investigates the unique winter phenomenon in central China's Twain‐Hu Basin where high aerosol optical depth (AOD) centers coincide with a regional near‐surface wind speed maximum. Based on multi‐decadal reanalysis data sets, satellite retrievals, ground observations, and FLEXPART‐WRF simulations, we demonstrate that strong ventilation‐driven regional aerosol transport dominates the formation and interannual variability of high‐AOD centers. The synergistic effects of the anomalous synoptic‐scale conveyor belt, intensified boundary‐layer ventilation, and the basin's funnel topography enhance regional aerosol transport and convergence, while high humidity and stable stratification aloft further promote vertical redistribution and accumulation. During high‐AOD years, regional transport contributes 56.46% to PM _2.5 concentrations, and ventilation coefficients explain ∼68% of AOD variance. A U‐shaped relationship emerges between AOD interannual variability and ventilation, indicating a shift from local‐accumulation‐dominated mild pollution to transport‐driven severe pollution. These findings challenge the conventional “stable synoptic mode” paradigm and advance understanding of receptor‐region pollution dynamics.