Trends in the different grades of precipitation over Guangxi province, south China, during 1980-2008 and the possible causes

Abstract

Global warming and the aerosol effect have both been proposed as possible causes of the changes in precipitation intensity (PI). Using daily data in Guangxi province, south China, during 1980–2008, the variation of different grades of precipitation was analysed and the possible causes are discussed. It was found that a declining trend occurs in low-grade precipitation and an increasing trend occurs in high-grade precipitation, which increases PI. However, the contribution from the increase in high-grade precipitation is offset by the decrease in low-grade precipitation, and thus total precipitation shows no significant trend. The relation between surface vapour pressure and PI was analysed to reveal the global warming effect on precipitation, and it was found that PI increases with increasing surface vapour pressure. In general, a difference between polluted and unpolluted areas was found in drizzle precipitation rather than small/medium/large/heavy precipitation; since drizzle precipitation makes little contribution to total precipitation and PI, it is concluded that global warming rather than the aerosol effect might be the primary cause of the increasing PI in the study area on a yearly timescale.