The Evolution And Driving Forces Of Drought Based On The New Comprehensive Drought Index

Drought is a kind of worldwide natural disaster,which has been troubling many provinces and regions in China.It may reduce agricultural production,weaken industries,af:fect the life of people,and hinder the development of our society.Drought index research is the only way of drought research.In order to solve the problem of drought disaster systematically,the study of multi-variable comprehensive drought index has become the general trend.In this paper,based on the existing research on drought index,a Standardized Drought Index(MSDI)combining two variables that can comprehensively characterize meteorological Drought and hydrological Drought is developed.By comparing the MSDI index with the traditional univariate drought index SPI(standardized precipitation index)and SRI(standardized runoff index),the superiority of the MSDI index in characterizing comprehensive drought is verified.By comparing the MSDI index with the MSDIp index,the improvement of the MSDIp index(the MSDI index fitted by parameter marginal distribution)was verified.A series of methods including mann-kendall test,heuristic segmentation,wavelet analysis and cross wavelet were used to analyze the evolution characteristics of MSDI index and the driving force behind it.The conclusion is as follows:(1)For the distribution fitting of hydrological elements,the non-parametric kernel estimation method can overcome the complex steps of selecting the best fitting distribution for different hydrological elements in different regions,and the fitting effect of non-parametric kernel estimation is good,which can replace the traditional parameter fitting method.In addition,the non-parametric kernel estimation method was used to fit the marginal distribution,which avoided the problem that the MSDIp index would amplify the drought and exaggerate its severity;(2)Through the month of whole basin of Weihe river basin scale MSDI with single variable SPI index were compared with SRI index,analyzed the MSDI index in different comprehensive drought situation represent different categories of drought situation and specific meaning,verify its superiority on characterization of actual comprehensive drought:MSDI could make up for a single variable drought index of drought depicting too one-sided problem;(3)By comparing the MSDI index with the drought-related data,it was found that the MSDI index had a good correlation with agricultural disaster loss data and Grace satellite water reserve data,and the MSDI index indeed had certain ability to represent the actual drought situation and early warning ability;(4)The comprehensive drought evolution characteristics of Weihe river basin based on MSDI index was studied and found to be the comprehensive drought evolution of Weihe river basin.The MSDI of the drought index showed a significant downward trend and showed variation.The first variation point occurred in 1994 and the second variation point occurred in 1971.The comprehensive drought of Weihe river basin has a large cycle of 22?23 years and a small cycle of 6?7 years;(5)By comparing MSDI under measured runoff with MSDI under reduced runoff,it was also obtained that the relative contribution rate of direct human activities to MSDI variation was 66.60%around 1971.Around 1994,the relative contribution rate of direct human activities to MSDI variation was 17.g9%.It indicates that compared with the direct human activities of industrial water,agricultural water and residential water,the indirect human activities such as climate change,greenhouse gas emissions,accelerated urbanization,and the transformation of underlying surface of the river basin have greatly increased their influence on the comprehensive drought of Weihe river basin;(6)The driving force of comprehensive drought evolution in Weihe river basin is analyzed,and it is found that the influence of precipitation and runoff on comprehensive drought in Weihe river basin is mainly short-term fluctuation.In the long-term fluctuation of different remote correlation factors,sunspots have the strongest influence on the comprehensive drought of Weihe river basin.Among the short-term changes,AO has the strongest influence on the comprehensive drought in weihe river basin.Sunspots have influence on precipitation,runoff and abnormal factors of atmospheric circulation.In addition to direct effect,sunspots can also exert influence on comprehensive drought of Weihe river basin through indirect effect.