Temporal And Spatial Distribution Characteristics Of Aerosol Optical Thickness And Its Influencing Factors In China And Typical Area

The aerosol optical thickness(Aerosol Opitcal Thickness,AOT or Aerosol Opitcal Depth,AOD)is fundamentally related to atmospheric turbidity,and a key factor in determining the climate effect of aerosols.Haze events become more and more serious in China.The increase of aerosols and haze pollution are closely linked,but the impact of specific human activities is unclear.Therefore,the analysis of the correlation between the long period AOT and human activities has a practical significance for the scientific prediction and effective monitoring of the regional atmospheric pollution and the government to control the atmospheric environment.Meanwhile,the study on the temporal and spatial distribution of long period aerosol optical thickness is the basis to analysis the aerosol climate effect,and the key to study the interaction between aerosol and global warming,the southern flood and northern drought and the monsoon rain belt moving.Based on the aerosol optical thickness data of MODIS and ATSR,AERONET aerosol optical thickness data and the statistical data of National Bureau of statistics of China(except the South China Sea Islands),the temporal variation and spatial distribution of AOT in China and Yangtze River Delta from 1995 to 2015 were analyzed.We focus on the impact of human activities(energy consumption structure,car ownership,high pollution industry products and urban construction)on AOT in the Yangtze River Delta region from 1995 to 2015.The main results are summarizedas follows:1)The aerosol optical depth in China has a significant upward trend,which can be divided into 3 stages:1995-2002(the first stage)and 2010-2015(the third stage)shown an upgrade trend,and the 2002-2010(the second stage)fluctuates.AOT is the highest in winter,followed by spring and autumn,the fastest growth in autumn,spring and summer increase is not significant.The monthly AOT curre in China is in wave shape,the highest value appears in February,whereas the lowest value in September.In space distribution,The Yangtze River Delta is mainly the high value area of AOT.2)The AOT yearly change in Yangtze River Delta is consistent with that of the national’s,and plays a stimulating role with the rate of 82%.However,the AOT grown faster than the national’s in the first stage,the third stage is on the opposite.The AOT monthly change over Yangtze River Delta is in "W" shape,the maximum value appeared in January,low value in July to September,the smallest in September.The value of AOT was higher in autumn and winter than in spring and summer.Autumn increase trend is most obvious.3)As for spatial distribution,the high value area of AOT distributed in the low-lying northern plains,and the low value area distribution in the hilly area of southern.The maximum value of AOT appears in the western and northern regions of Shanghai.Based on morlet wavelet analysis shows that,there are multiple time scale features are identifiedin the whole region of Yangtze River Delta in 1995-2015.The main period is 18 months.This is similar to the North-South climate periodic variation.The AOT yearly change in Yangtze River Delta has a pulling effect on the national AOT’s change,especially in December.In addition,Yangtze River Delta is a relatively AOT high value area in China,and its seasonal fluctuations is greater than the national’s,4)Transportation,high pollution industry production and fossil energy consumption and other human activities(especially the car ownership),have relatively large impact on the Yangtze River Delta AOT.