Search

Aerosol variability is influenced by changes in emissions and atmospheric dynamics. The aim of this study is to identify the role of synoptic weather systems in affecting the aerosol variation over East Asia under future changes in atmospheric dynamics. First we investigate the influence of synoptic weather on aerosol optical depth (AOD) spatiotemporal variability using long-term observations from Moderate Resolution Imaging Spectroradiometer (MODIS). We demonstrate that the major synoptic weather patterns of each season are among the dominant factors that affect AOD variations. During spring and autumn, AOD variability is significantly influenced by dynamic transport under northeasterly (winter monsoon) or southwesterly (summer monsoon) conditions. In summer, the maximum anomaly of the AOD variability was associated with the occurrence of fronts and tropical cyclones near Taiwan. While in winter, cold surge was the major event controlling the AOD variability. As atmospheric dynamics are well connected with AOD interannual variability, the AOD predictability over East Asia is associated with the predictability of synoptic weather systems. We apply the high-resolution atmospheric model (HiRAM) to identify these weather systems in present climate and under future warming scenarios. Under future climate based on HiRAM, the occurrence of summer tropical cyclones decreases by 32%, and the autumn southwesterly pattern increases by 50%. Considering the frequency change in summer tropical cyclones and autumn southwestlies under future scenarios, this may lead to the accumulation of AOD over China during summer and autumn through dynamic transport. The results suggest that AOD variations in East Asia may change along with future changes in the large-scale circulation under global warming. • Transport under monsoons notably altered aerosol variability in spring and fall. • In summer, AOD variability was highly linked to fronts and cyclones near Taiwan. • Cold surge was the major event controlling the aerosol variability in winter. • The future change in event frequency may lead to aerosol accumulation over China. [ABSTRACT FROM AUTHOR]

We constructed the A-Train co-located aerosol and marine warm cloud data from 2006 to 2010 winter and spring over East Asia and investigated the sensitivities of single-layer warm cloud properties to aerosols under different precipitation statuses and environmental regimes. The near-surface stability (NSS), modulated by cold air on top of a warm surface, and the estimated inversion strength (EIS) controlled by the subsidence are critical environmental parameters affecting the marine warm cloud structure over East Asia and, thus, the aerosols–cloud interactions. Based on our analysis, precipitating clouds revealed higher cloud susceptibility to aerosols as compared to non-precipitating clouds. The cloud liquid water path (LWP) increased with aerosols for precipitating clouds, yet decreased with aerosols for non-precipitating clouds, consistent with previous studies. For precipitating clouds, the cloud LWP and albedo increased more under higher NSS as unstable air promotes more moisture flux from the ocean. Under stronger EIS, the cloud albedo response to aerosols was lower than that under weaker EIS, indicating that stronger subsidence weakens the cloud susceptibility due to more entrainment drying. Our study suggests that the critical environmental factors governing the aerosol–cloud interactions may vary for different oceanic regions, depending on the thermodynamic conditions. [ABSTRACT FROM AUTHOR]

Intense economic and industrial development in China has been accompanied by severe local air pollution, as well as in other downwind countries in East Asia. This study analyzes satellite observational data of sulfur dioxide (SO2), nitrogen dioxide (NO2), and aerosol optical depth (AOD) to explore the spatial distribution, long-term temporal variation, and correlation to meteorological conditions over this region over the period 2005–2015. SO2 and NO2 data are retrieved from the ozone monitoring instrument (OMI) onboard the National Aeronautics and Space Administration (NASA) Aura satellite, while AOD data are from the moderate-resolution imaging spectroradiometer (MODIS) onboard the NASA Aqua satellite. Spatial distributions of SO2, NO2, and AOD show the highest levels in the North China Plain (NCP), with hotspots also in Southeastern China (SC) and the Sichuan Basin (SB). Biomass burning also contributes to a high level of AOD in Southeast Asia in spring and in Equatorial Asia in fall. Considering the correlation of pollutant levels to meteorological conditions, monitoring data show that higher temperature and higher relative humidity (RH) favor the conversion of SO2 and NO2 to sulfate and nitrate aerosol, respectively. The impact of stronger lower tropospheric stability facilitates the accumulation of SO2 and NO2 in NCP and SC. Transport of SO2 and NO2 from intense source regions to relatively clean regions is highly influential over East Asia; such transport from the NCP leads to a considerable increase of pollutants in SC, SB, Taiwan Island (TW), and Taiwan Strait (TWS), particularly in winter. Aerosols generated by biomass burning in Southeast Asia and anthropogenic aerosol in SC are transported to TW and TWS and lead to the increase of AOD, with the highest levels of AOD in SC, TW, and TWS occurring in spring. Precipitation results in the removal of pollutants, especially in highly polluted regions, the effect of which is most significant in winter and spring. [ABSTRACT FROM AUTHOR]