Analysis Of The Long-term Trend And Variation Mechanism Of Dust In East Asia

East Asian dust aerosols play a vital role in the global and regional climate through its direct,indirect,and semidirect effects.Examining the long-term trends of dust aerosols in East Asia and factors affecting them is critical for both understanding and predicting the variation pattern of dust in East Asia.We verified the applicability of MEERA-2 dust data in East Asia,and analyzed the interannual trends of dust aerosols in East Asia during the dusty season(March–July)from 2000 to 2019 using the MERRA-2 data and identified the dominant factors affecting the interannual variation during the dusty season(March–July)by developing the regional multiple linear regression models,combined with correlation and partial correlation analysis.Analysis of the typical dust storm event in east Asia from May 2 to 7,2017indicated that although there is some uncertainty about the source of dust emission in the MERRA-2 model,the data accurately simulated the evolution of the dust event and analyze it comprehensively.The description of the spatiotemporal distribution and variation of the dust aerosols in the dust event using the MERRA-2 data is consistent with the data of AERONET,National Urban Air Quality Real-time Publishing Platform and Hamawari-8.Gobi Deserts was the most influential source area of this dust event with the highest emissions reaching 1.9×10~6g/m~3.The vertical motion of the atmosphere can lift dust from the source area above 500 h Pa.There were low-pressure troughs at 500 and 850 h Pa and the winds behind and in front of the trough led to the high-altitude,long-distance transport of dust.Dust gradually affected the northwest China,north China,northeast China and even the ocean and Japan from May 2 to 7.The comparison with the dust index(DI)calculated from ground-based observations of dust events frequency indicated that MERRA-2 DCMD exhibited high spatial agreement(R>0.8)with ground-based observations in most regions(especially in the dust source region of North China).The trend analysis revealed that DCMD in East Asia decreased significantly after2000,particularly in the dusty season(March–July).These significant decreases were generally highly correlated with increases in normalized differential vegetation index(NDVI),volumetric soil moisture(VSM),and precipitation(PPT)and with decreases in wind speed(WS).Furthermore,WS nearly dominated the interannual variation in the dust concentration over the East Asian dust source regions and their downstream.By contrast,PPT,through its wet deposition effect,dominated the variation in the rest of the regions away from the dust source regions.