Analysis Of Drought Characteristics And Assessment Of Drought Risk In Xinjiang

In the context of global warming,extreme drought events are increasing.As a typical arid area,Xinjiang is sensitive to global climate change.It is urgent to alleviate the severe drought situation in Xinjiang due to frequent drought disasters.Object: To identify the drought process in Xinjiang and analyze the temporal and spatial characteristics of drought,systematically study the meteorological drought characteristics in Xinjiang,analyze the joint distribution characteristics of multidimensional drought characteristic variables,in order to obtain the joint distribution probability of drought characteristic variables and drought recurrence period;It can provide scientific basis for formulating reasonable and effective drought risk management system to clarify drought risk factors,evaluate drought risk and regionalize drought risk in Xinjiang.Methods: Based on the daily precipitation,temperature,sunshine and evapotranspiration data of 60 national meteorological stations in Xinjiang during 1960-2021,the daily meteorological drought composite index(MCI)of each station was calculated and drought grade was divided.On the basis of identifying the drought process based on the run theory,the M-K mutation test,Morlet wavelet analysis and Rotation empirical orthogonal function(REOF)were used to analyze the spatio-temporal variation of meteorological drought in Xinjiang.The marginal distribution function was used to fit the three typical drought characteristic variables,the optimized Copula function was used to establish the two-dimensional and three-dimensional joint distribution model among the drought characteristic variables,the joint distribution probability of the drought characteristic variables and the drought return period were calculated.Based on the four-factor theory of natural disaster risk,the index system and evaluation model of disaster risk were constructed,the drought disaster risk regionalization in Xinjiang was carried out by combining GIS technology.Results:(1)In the interannual variation,the number of drought processes in Xinjiang showed a decreasing trend.From 1960 to 2021,the total number of drought processes in northern Xinjiang was higher than that in southern Xinjiang.Xinjiang is prone to drought in spring,and it is prone to continuous drought in spring and summer.the number of drought processes in each region showed a slow decreasing trend in the interannual variation,which was consistent with the overall trend of drought in Xinjiang.(2)In the recent 62 years,the overall degree of meteorological drought in Xinjiang has been slowly alleviated and the climate has gradually become warmer and wetter.The time series of drought intensity had a sudden change in 1986 and the time series of drought duration had a sudden change in 1978.The high-grade drought process with high intensity and long duration gradually decreased.The long time scale of 25-48 years is the main frequency of drought evolution in Xinjiang.(3)The spatial distribution of drought characteristics was significantly different.The average annual drought intensity in northern Xinjiang was stronger than that in southern Xinjiang,the duration of drought was longer than that in southern Xinjiang.The number of drought days in each region decreased significantly with the increase of drought grade.The seasonal characteristics of drought in Xinjiang showed obvious differences.Spring was prone to drought in the whole Xinjiang,summer drought worsened from south to north and autumn drought was light on the whole.After REOF decomposition,the first spatial mode shows the opposite pattern in southern and northern Xinjiang,the second spatial mode shows the consistent pattern in the whole Xinjiang.The corresponding time coefficient can reflect the severe drought years.(4)In Xinjiang,the probability of long duration and high intensity extreme drought events is small,while the probability of short duration,low intensity and low peak value drought processes is relatively large.The generalized extreme value distribution function can better fit the drought intensity and drought duration,the Weibull distribution function can best fit the drought peak,Gumbel Copula function can better fit the drought intensity and drought duration two-dimensional joint distribution.The Clayton Copula function has better fitting results in the two-dimensional joint distributions of drought duration-peak and intensity-peak,the Clayton Copula function has the best fitting effect in constructing the three-dimensional joint distribution.(5)There are obvious spatial differences in the comprehensive risk of drought disaster in Xinjiang,with a higher risk in northern and southern Xinjiang and a lower risk in central Xinjiang.The risk of drought-causing factors showed a decreasing trend from northern Xinjiang to southern Xinjiang.The spatial distribution of vulnerability to a disaster-bearing environment in southern Xinjiang was stronger than that in northern Xinjiang.The exposure level of disaster-bearing bodies showed a stepwise decreasing trend from western to eastern regions,the spatial distribution of disaster prevention and reduction ability was higher in the middle and lower at both ends.Conclusion: MCI index can accurately monitor the time and region of meteorological drought,which has good applicability in Xinjiang.Copulas function can describe the joint distribution of multi-dimensional drought characteristic variables in Xinjiang;from 1960 to 2021,the overall degree of meteorological drought in Xinjiang is slowly weakening and the drought situation is worsening from southern Xinjiang to northern Xinjiang.The risk of drought disaster is larger in northern and southern Xinjiang.Therefore,the risk management system for drought disaster in northern and southern Xinjiang should be improved,the drought monitoring and control measures should be further strengthened.