Drought Trend Assessment for the Middle Reaches of Yellow River Based on Standard Precipitation Index under Climate Change

摘要

The middle reaches of Yellow River is one of districts liable to severe drought in China,while the drought trend has become increasing recently as global climate change intensifying.In this study,standard precipitation index (SPI) was employed as drought index,and an improved SPI approach was proposed for better drought representation.The SPI degrees of ten-day series were calculated for Shanxi province located in the middle Yellow River for 40 years from 1970 to 2009.The results show the improved SPI could represent the historical drought situation of this district in a better manner.Allowing for the future drought trends impacted by climate change,the current widely used climate scenarios all over the world——four GCM (CSIRO,NCAR,MPI,PRECIS) projections during the 21st century under four IPCC SRES emission scenarios (A1B,A2,B1,B2)——were imported.The Delta change approach was employed to correct the systematic biases in GCM projections.The drought situations of Shanxi province during2021 to 2050 were analyzed under future climate scenarios.Thus they were compared with the historical period from 1971 to 1999 in terms of inter-annual variation of drought level.The historical drought formation,development regularity and possible future situation were deduced.The results show under future climate change the drought would show the possibility of more critical against water supply and agriculture production.In view of the uncertainty of future climate change,though not very high possihility for more serious drought,it still should be paid more attention by water resources management.