| Drought has become one of the serious environmental problems that threaten human survival.With the increase of population and economic development,the scope of the drought impact has become larger and larger,and the resulting losses have become more and more serious.In recent years,global warming has accelerated,and natural disasters in agriculture have become more frequent,drought has not only directly led to agricultural production cuts,food shortages,high incidence of diseases,insect pests,and reduced productivity of crops,its continuous accumulation also lead to the degradation of land resources,the depletion of water resources and the destruction of the ecological environment,thus constraining the sustainable development of agriculture.Agricultural drought is a kind of chronic natural disaster with extremely high uncertainty,it has more harm to social and economic development than any other natural disaster.Therefore,based on the analysis of the temporal and spatial evolution characteristics of drought in Shaanxi Province,this paper evaluates the agricultural drought vulnerability and formulates the drought relief policy for the government to provide a scientific basis for reducing drought losses.The main research results of the paper are as follows:(1)Study on the Applicability of Meteorological Drought Index in Shaanxi ProvinceTaking the monitoring data of precipitation and temperature from 19 meteorological stations from 1961 to 2016 in Shaanxi Province as the raw data,two standardized drought indices(SPI)and standardized precipitation evapotranspiration indices(SPEI)were selected to respectively calculate the monthly SPI1,SPI3,SPI6,SPI12 and SPEI1,SPEI3,SPEI6,SPEI12,and then analyzing the basic characteristics of drought,the interannual characteristics of regional drought and the ratio of drought stations in four time scales of 1,3,6,12 in Shaanxi Province.Comparing the results of the two indicators,and verifying the actual occurrence of drought disasters in different regions of Shaanxi Province recorded in the Shaanxi Province Drought Disaster Yearbook,it was found that the SPEI value analysis results are closer to the actual situation,at the same time,the SPEI3 index reflects the trend of the seasonal drought ratio in different regions more obvious than SPI,so SPEI index was chosen to analyze the spatial and temporal evolution characteristics of drought in Shaanxi Province.(2)Analysis of Spatial and Temporal Characteristics of Drought in Shaanxi Province Based on Wavelet TheoryIn spatial,based on the selected drought index calculation results SPEI1,SPEI3 and SPEI12,using the inverse distance weighted(IDW)interpolation method of ArcGIS 10.2,the annual scale,spring,summer,autumn and winter seasons scale and monthly scale spatial distribution map of drought frequency scale and the spatial distribution map of drought frequencies at different levels were obtained respectively,which provide a comprehensive analysis of the temporal and spatial evolution characteristics of drought in Shaanxi Province from 1961 to 2016.In time,the paper introduced in the wavelet theory and used MatlabR2015 b,comprehensively considering characteristics such as wavelet similarity,orthogonality,vanishing moment,and length of support,and contrastively analyzing the correlation and applicability of wavelet function and drought data analysis of drought characteristics,finally the demy wavelet base was selected,and 9 layers were used as the decomposition layer to decompose the SPEI12 index of the province,northern Shaanxi,southern Shaanxi,and Guanzhong by wavelet analysis,which systematically analyzed the drought trend,periodic characteristics,and mutation characteristics.(3)Construction of Agricultural Drought Vulnerability Evaluation Index System based on Principal Component Analysis(PCA)and Entropy Weight Method in Shaanxi ProvinceIn order to enable the selected indicators and influencing factors to comprehensively and objectively reflect the essential characteristics of regional agricultural drought vulnerability,the paper selected 30 evaluation of risk,exposure,sensitivity,and ability in systematic,representative,accessible and dynamic principles which based on the explaination of the formation mechanism of agricultural drought vulnerability.The principal component analysis method of SPSS19.0 software was used to quantitatively analyze the index data,and according to the eigenvalue ?(29)1and cumulative variance contribution rate of more than 90% to extract the first six principal components,then selecting the index with larger factor to enter the main component to determine 20 evaluation indicators as evaluation indicators of agricultural drought vulnerability in Shaanxi Province.Finally,the entropy weight method was used to determine the weight of each index,and then established the Shaanxi Provincial Agricultural Drought Vulnerability Evaluation Index System and the corresponding weight system.(4)Study on Evaluation Method of Agricultural Drought Vulnerability in Shaanxi ProvinceSince the agriculture drought vulnerability is affected by many factors such as natural,social,and economic factors,this paper has used administrative location units and 10 cities in Shaanxi Province as the research object,choosing the pair analysis method and the improved TOPSIS algorithm to comprehensively evaluate agricultural drought vulnerability,and ArcGIS 10.2 software was used to map the agricultural drought vulnerability in Shaanxi Province.Comparing the evaluation results of the two algorithms,which all showed that the drought vulnerability of agriculture in Shaanxi province gradually increased from north to south.and the assessment results of risk,sensitivity,and drought resilience are relatively consistent,which verifies the rationality of the two algorithms in agricultural drought vulnerability assessment.At the same time,the contributions of the 20 evaluation indicators were calculated using the factor contribution model to find the main contribution factors of agricultural drought vulnerability in each region.(5)Agricultural Drought Risk Management and Countermeasures for Drought and Disaster Reduction in Shaanxi ProvinceSummarizing the international advanced experiences in the management of drought disasters,and analyzing the causes of agricultural drought in Shaanxi Province and the current status and problems of drought management in Shaanxi Province based on an analysis of the current status and development direction of drought management in China.Combining the natural,social and economic development characteristics of Shaanxi Province and the current status of drought management,taking into account factors such as the distribution characteristics of agricultural drought vulnerability in different regions,and the main impact factors and impact degree,etc.,the paper proposed agricultural drought Disaster reduction countermeasures for northern Shaanxi,Guanzhong and southern Shaanxi respectively. |
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