Analysis Of Drought Characteristics In The Sanjiangyuan Region And Prediction Of Future Drough

In this study,IDW interpolation,Mann-Kendall test,Morlet wavelet analysis,run theory,SDSM model and other methods and tools were used to systematically analyze the rule of spatio-temporal variation and trend periodic changes with precipitation,temperature and evapotranspiration in the Sanjiangyuan region,to laid the foundation for drought analysis;Secondly,SPI,MI,SPEI and MCI were selected to analyze the spatio-temporal variation characteristics of different drought indexes and their drought characteristics(drought frequency,drought duration,drought intensity),and to assess the applicability of the drought indices in combination with NDVI,to determine the optimal drought indices for the Sanjiangyuan region;finally,the SDSM model was used to downscale the Can ESM5 and Nor ESM2-MM climate model data into station data,to realize the future drought prediction under different climate scenarios.The main conclusions are as follows:(1)The climate of the Sanjiangyuan region from 1979 to 2014 is characterized by a clear warming and humidification,with a significant increase in evapotranspiration,temperature and precipitation show a distribution pattern of increasing from northwest to southeast,and evapotranspiration is characterized by high distribution in the south and northeast and low distribution in the northwest and central parts.The average annual temperature,precipitation and evapotranspiration growth rates are 0.5°C/10a(p<0.01),17.8mm/10 a and 14.1mm/10a(p<0.01)respectively.The increase in average annual temperature is due to the increase in temperature in all seasons,the increase in annual precipitation is due to the increase in spring precipitation and the increase in annual evapotranspiration is due to the increase in evapotranspiration in autumn and winter.(2)The spatial distribution of SPI,SPEI,MI and MCI increased from northwest to southeast,while drought events decreased from northwest to southeast in the Sanjiangyuan region during 1979-2014.From 2000 to 2014,20%,51%,12%,16% and 1% of regional vegetation were significantly improved,slightly improved,stable,slightly degraded and seriously degraded,respectively.The drought frequency,duration and intensity of SPI,SPEI and MCI were relatively consistent in spatio-temporal distribution,and decreased from northwest to southeast.The Tuotuohe,Wudaoliang,Maduo,Yushu and Xinghai were high incidence areas of deought,and the MI index had excessive drought evaluation,which was not suitable for drought monitoring in Sanjiangyuan region.NDVI was negatively correlated with drought frequency,drought duration and drought intensity,SPI and MCI had the strongest correlation with NDVI(p<0.01),SPI and SPEI had the best correlation with drought intensity and NDVI(p<0.05).The correlation between NDVI and drought index and drought characteristics showed that,The SPI index has the best applicability in drought monitoring in the Sanjiangyuan region.(3)The SDSM model based on the calibration of NEP-DOE and the measured precipitation at weather stations during 1979-2014 has good applicability in the Sanjiangyuan region,and the measured precipitation at stations is relatively consistent with the simulated precipitation of SDSM model.In the three scenarios from 2025 to 2100,drought events in the Sanjiangyuan region decreased significantly.Under ssp126,drought events and wet events occurred alternately,and the whole region was in a state of dry-wet balance.Under ssp245 and ssp585,dry and wet changes were relatively stable.The two scenarios are dominated by drought events before 2050 and 2060,and then show continuous wet events.Before the middle of the 21 st century,the drought situation in the Sanjiangyuan region will still be severe,and ecological protection should be continued.