Spatial And Temporal Variability Of Aerosol Optical Depth In China Based On MERRA-2 Data

Aerosol optical depth(AOD)is a key physical quantity that characterizes atmospheric turbidity and a key factor in determining the aerosol climate effect.Extensive economic development methods have brought serious air pollution to my country.Full understanding of the spatiotemporal characteristics of different types of AOD is conducive to providing effective data support for atmospheric environmental governance.Meanwhile,the study of the temporal and spatial changes of the AOD long-term sequence is the basis for analyzing the aerosol climate effects,and is also the key to studying the interaction of aerosols with global warming,floods in south and droughts in north,and monsoon rain belts.Based on the reanalyzed AOD data of MERRA-2,the temporal and spatial changes of four different types of aerosols in black carbon,sand,sea salt and sulfate AOD from 1980 to 2018 in China(excluding the South China Sea islands)were studied.And the characteristics of the spatiotemporal variation of the AOD of four types of aerosols in four typical areas in the past 40 years were analyzed.The main conclusions of this study are as follows:(1)The AOD of the four types of aerosols all showed an upward trend,of which the sulfate AOD had the largest upward trend.The annual changes in AOD of the four types of aerosols in typical regions were synchronized with the annual changes in the AOD of the four types of aerosols in China,and the upward trend was greater.(2)The AOD of the four types of aerosols had obvious seasonal changes.Black carbon AOD was the largest in spring,and the spring had the most obvious upward trend over the years.The Beijing-Tianjin-Hebei region had the most affected by summer.Sea salt AOD has the most obvious upward trend in summer in the country and its typical regions,but it was the largest in the country in spring.The seasonal changes of dust and sulfate AOD in China and typical areas are consistent with the trend changes.(3)From 1980 to 2018,four types of AOD have multi-time-scale characteristics in China and typical regions.The four types of periodic oscillations with large AOD above 20 a have full-time domain and large energy,while there were differences in periodic oscillations on medium time scales and smaller time scales.In the overall change trend,only sulfate AOD showed a downward trend on the time scale shorter than 20 a.(4)The spatial variation trends of black carbon,sea salt and sulfate AOD in China all showed the distribution pattern of high in the east and low in the west.Black carbon had formed the spatial variation pattern of high in the south and low in the north but the sulfate AOD showed the pattern of high in the north and low in the south in typical regions.The high values of the spatial variation trend of dust AOD in China were concentrated in the northwest region,especially in the north of southern Xinjiang,and the low value regions were mainly distributed in north China and northeast China.