Analysis On The Characteristics Of Regional Drought Change In China

With the continuous intensification of climate change and global warming,as a high-impact extreme event,drought changes have attracted more and more attention from humans and society.In-depth research is needed on drought changes in different regions over China.And the research and evaluation of the drought indices is the key to analyze and quantify the drought and its changes and impact.Based on in-situ meteorological datasets,reanalysis grid datasets,satellite retrieval vegetation datasets and model dataset,this paper analyzes the drought changes in different regions over China,the response of vegetation on drought changes and projection in key research areas using a series of climate statistics and data processing methods.Research shows that:(1)the FAO Penman-Monteith algorithm to calculate the potential evapotranspiration instead of the Thornthwaite has a good improvement effect on standardized precipitation evapotranspiration index(SPEI),and a trend of distribution over China is consistent with standardized precipitation index(SPI),meteorological drought composite index(MCI)and Palmer drought severity index(PDSI).The soil moisture(SM)in summer during 1979-2019 has shown good correlation with the four indices except for individual regions.In Northwest China,the middle and lower reaches of the Yangtze River,South China,the conclusion that the drought in the summer of1961-2019 tends to slow down is reliable.(2)This study further reveals that the precipitation in growing season shows a significant increase over most parts of the central and eastern Tibetan Plateau during 1961-2019.Consequently,drought conditions have generally relieved;And the analysis dataset basically reflects the changes of precipitation and drought in the entire Tibetan Plateau.Combined the vegetation index,due to the decrease of drought area coverage over Tibetan Plateau from 1982 to 2015,the coverage of bare land decreased,and the coverage of grassland and shrub vegetation increased significantly.The cumulative NDVI has increased significantly in growing season over Tibetan Plateau,and the vegetation has improved.Spatially,the vegetation in most of the northern part of Tibetan Plateau improved significantly,and in some areas in the southeast is deteriorating,whose main reason is drought aggravation;(3)Based on datasets simulated by 10 models of CMIP6,the analysis shows that under different emission scenarios,the Tibetan Plateau shows an increase in precipitation in the future.Among them,in the high-emission scenario(SSP5-8.5),the trend of precipitation increase over Tibetan Plateau is the largest,with a trend of 3.87%/10a(p < 0.05).And the degree of drought mitigation is different under different emission scenarios over Tibetan Plateau.As emission scenarios continue to increase,the future "warming and wetting" characteristics over Tibetan Plateau will become more obvious.