Change of the solar radiation and its causes in the Haihe River Basin and surrounding areas

Solar radiation is an important driving force for the formation and evolution of climate system. Analysis of change in solar radiation is helpful in understanding mechanism of climate change. In this study, the temporal and spatial variations of solar radiation and the cause of the change in solar radiation have been analyzed based on meteorological data from 46 national meteorological stations and aerosol index data from TOMS over the Haihe River Basin and surrounding areas. The results have shown that solar radiation and direct radiation significantly decreased, while scattered radiation increased during the period 1957–2008. Spatially, the decreasing trend of solar radiation was more and more significant from low population density areas to high population density areas. The spatial distribution of increase in aerosol index is consistent with that of decrease in solar radiation. The increase in aerosols resulting from human activities was an important reason for the decrease in solar radiation.