Dynamic Change Of Propagation From Meteorological Drought To Hydrological Drought And The Driving Forces

With the changing of global climate,meteorological drought and hydrological drought events occur frequenctly in the Wei River Basin,With the rapid development of social economy in the basin,the drought risk and its influence are increasing.Therefore,in the changing environment,the study on the dynamic change and driving forc.e of the propagation from meteorological drought to hydrological drought in the Wei River Basin can provide more reasonable and scientific basis for drought monitor and drought relief in this basin,and the research has important theoretical significance and application value.The main research results of this paper are as follows:(1)The standardized precipitation index(SPI)and the standardized runoff index(SRI)were calculated based on the monthly precipitation and runoff data in the Wei River Basin,which represented the meteorological drought and hydrological drought,respectively.And analyzed the spatial and temporal distribution characteristics of the meteorological drought and hydrological drought in the Wei River Basin.The results indicate that the frequency of meteorological drought in the Wei River Basin is higher than hydrological drought,but the average duration and intensity are less than hydrological drought;the duration of meteorological drought is longer in the northwe.st than it in the southeast,and the intensity is the smallest in the Jing River Basin.Meteorological drougtht and hydrological drought all show more serious trends,and the severity is greater in the west than in the east.(2)Based on the multi-time-scale of SPI,the propagation time from meteorological drought to hydrological drought in different seasorns were calculated,and the dynamic change of the propagation time was analyzed by a sliding window.The results indicate that the propagation time from meteorological drought to hydrological drought is about 3 months,and there are differences in different seasons.The propagation time is about 2 months in spring and 3 months in summer and autumn,18 months in winter.According to the analysis of the dynamic change,the propagation time in summer and autumn,18 months in winter.According to the analysis of the dynamic change,the propagation time in spring and winter tends to be shorter,and in summer and autumn tends to be longer.(3)The influence factors on drought propagation was analyzed,and the multiple linear regression was used to quantitatively explore the explanation of different factors.Results indicate that the meteorological factors(Precipitation and Arid index)have great influence on drought propagation in spring,the factors are not significant in summer,the influence of meteorological factors(Potential evapotranspiration and Arid index)and teleconnection factors(ENSO,AO,PDO)are the dominant factors in autumn,and all factors have strong correlations in winter.Multiple linear regression analysis shows that considering meteorological factors,teleconnection factors and underlying surface feature will have a better performance of drought propagation in the Wei River Basin.(4)The Copula-based Likelihood-ratio(CLR)method was used to established the dependent structure between meteorological drought and hydrological drought,and explored the influencing factors of the dependent relationship.The results indicate that meteorological factors are the dominant factors of the relationship in spring and summer,underlying surface feature and meteorological factors are the dominant factors in autumn,the teleconnection factors and underlying surface feature are the dominant factors in winter.Compared with the linear driving force analysis of propagation time,the CLR method can better capture the driving force affecting the correlation between meteorological drought and hydrological drought.