Analyses on the Spatial Distribution of Aerosol Optical Depth over China in Recent 30 Years
Luo Yunfeng and Lu Daren(Institute of Atmospheric physics, Chinese Academy of Sciences, Beijing 100029)Zhou Xiuji and Li Weiliang(Chinese Academy of Meteorological Sciences, Beijing 100081)
With an improved retrieving method, the yearly and monthly mean 0.75 μm aerosol optical depths (AOD) are retrieved by using the daily direct solar radiation, sunshine duration, surface press'ure and vapor pressure data of 46 A-class solar radiation stations over China from 1961 to 1990, as well as the Total Ozone Mapping Spectrometer (TOMS) derived ozone data of 1979-1990. Then the analyses on the distribution of yearly mean AOD over China in recent 30 years are made from the derived AOD data. It is found that the patterns of yearly mean (1961- 1990) AOD generally have geographical features over the China mainland with a maximum lying in the Sichuan Basins except a few metropolises. One of the largest AOD centers is located in the Sichuan Basin east of 95°E, and the other in the south Xinjiang Basin west of 95°E. AOD distribution for each month is similar to that of the annual mean pattern in the "basin" effect is very significant, but the differences between each month are also obvious. The distribution of AOD in the 1960s is typically consistent with geographic feature, with largest centers in the Sichuan and southern Xinjiang basin, respectively. In the 1970s, AOD increased in the most China's areas, especially in east part of the Southwest China, the middle-and-lower reaches of the Yangtze River and southern coastal areas. In the 1980s, AOD increased rapidly in almost all areas except for west part of the Xinjiang Autonomous Region, and some areas of the Yunnan Province. Thus, the patterns of AOD distribution over China changed.