Temporal And Spatial Characteristics Of Aerosol Direct Radiative Forcing Under Clear Sky In The Indo-China Peninsula And The Indian Peninsula

Based on the data of aerosol optical thickness(AOD),horizontal transport divergence flux and surface net radiation flux under clear sky from 1980 to 2020 provided by Merra-2 reanalysis,this paper analyzes the aerosol optical thickness,surface aerosol direct radiation forcing(ADRF)under clear sky and their relationship with atmospheric short wave heating rate in Indochina Peninsula and Indian peninsula,then the aerosol direct radiative forcing under clear sky at the top of the atmosphere from 2012 to 2019 is estimated by using MODIS satellite data.Finally,the following conclusions are obtained:(1)Three large-value areas of AOD and radiative forcing were obtained by the time-space decomposition of EOF,namely the northern part of the Indian Peninsula(extending from the north to the southeast of the Thar Desert in northwestern India to Bangladesh and its coast),and the northern part of the Indo-China Peninsula(18-29°N,90-98°E),Vietnam and northern Laos bordering southern Yunnan Province(9-18°N,98-110°E).The average annual values of AOD and surface ADRF in these three regions and Yunnan Province(21-29°N,98-106°E)show an increasing trend over time.Before 2000,three regions had extreme values of AOD(0.3)and surface ADRF(-14W/m~2)in 1982-1983 and 1991-1992.On the post-2000 quarterly scale,AOD(0.3)and surface ADRF(-16W/m~2)were stronger in the northern Indian Peninsula in October-February and May-June,and the Indo-China Peninsula and Yunnan Province were stronger in 3-4 Monthly AOD(0.35)and surface ADRF(-24W/m~2)are strong.From 2012 to 2020,the emission and horizontal flux transport of local carbonaceous aerosols were strong in the north of the Indian peninsula from October to February,Bangladesh and its coastal areas from May to June,and the north of Laos and Vietnam on the Indo-China Peninsula from March to April,the central value of divergence is as high as 15 kg/m·d.(2)In estimating the monthly average shortwave direct radiative forcing of aerosols at the top of the atmosphere based on the daily data of MODIS and CERES from 2012 to2019 and the Multivariate linear fitting method,the radiative flux results fitted by the Multivariate regression are good with the original data,but the estimated radiative forcing obtained from the fitting is smaller than the radiative forcing from the reanalysis,and most of the research regions are underestimated.The radiative forcing estimate over the ocean is better than those over the land.(3)Based on the daily data from 2012 to 2020 and the monthly data from 1980 to2020 in the Indochina Peninsula from February to April and the Indian Peninsula from May to June,the direct radiative forcing of surface aerosols and the atmospheric shortwave heating rate at different altitudes were calculated.The results show that the stronger(weaker)the surface ADRF,the higher(lower)the atmospheric shortwave heating rate over the same area,the two variables are stronger in the north of Laos and Vietnam in March-April,and the value in March is higher and its coverage is wider;the two variables are stronger in the northern Indian peninsula in May-June,higher values in May also have wider coverage.The monthly mean values of surface ADRF and atmospheric shortwave heating rate in 2012-2020 were higher than those in 1980-2020,and there were mutation points in 2000 in the SVD time series in 1980-2020,and both variables changed from negative values to positive values indicate that the surface ADRF and heating rates are intensifying trends and become stronger after 2000.