supported by National High Technology Research and Development Program of China (Grant No. 2006AA10Z231);National Key Technologies R & D Program (Grant No. 2007BAD87B08);Chinese Universities Scientific Fund (Grant No. 2009-3-14)
Observations indicate that global radiation reaching the Earth's surface has gradually decreased over the past several decades(i.e.,the "global dimming" phenomenon),while the fraction of diffuse radiation in global ra...