Long term variation trends of aerosol optical depth in China from MODIS and toms

TOMS AOD at 500nm (1980-2001), combined with MODIS data (2000-2008) at 550nm, are used to perform trend analysis of AOD, temporally and spatially, over eight typical regions in China. The variation trends are as follows: firstly no notable upward or downward tendencies in AOD during 1980-1992 for the relative low value (-0.0006/decade), then during 1996-2001 a discernible ascending tendency with larger magnitude at 0.0231/decade, and finally, since 2000, a weak downward trend with -0.0017/decade. The large increases during 1990´s are presumably consequences of sharp increases in industrial and anthropogenic activities. In particular, in late 1990´s, only in Taklimakan Desert a negative trend with a maximum magnitude of -0.04/decade is detected. However, over regions such as Jingjinji and Pearl River Delta influenced by industrial activities, positive tendencies at +0.01/decade are observed.