Spatial–temporal Evolution Of Drought Characteristics Based On Z Index In Guizhou

Drought is a natural phenomenon of water shortage.Drought is called drought disaster because of its bad effect on human society's production,life and ecological environment.Drought disasters are directly related to water resources security,food and ecological security.The drought has been a major natural disaster facing humanity since ancient times.Drought disasters are directly related to water security,food security and ecological security.Drought is a global natural disaster that occurs frequently and has the characteristics of recurring and destructive.It has a serious impact on the social economy and people's lives.It is also a hot issue that academic circles attach great importance to.The agricultural drought in Guizhou Province,which is widely distributed in karst,is particularly significant and causes significant losses.Therefore,it is of great significance for drought monitoring,disaster analysis and formulation of effective drought prevention and resistance policies to select drought indicators reasonably to analyze the drought characteristics of long time series.The drought index is the quantitative expression of the degree of drought.Reasonable selection of drought indicators is of great significance for drought monitoring,disaster analysis,and effective drought and drought prevention policies.There are many drought monitoring indexes.From the meteorological,remote sensing,and remote sensing comprehensive monitoring indicators,the domestic and international drought monitoring methods are classified and summarized,and tries to make a comprehensive summary of drought research.In this context,this paper takes Guizhou Province as the research area,analyzes the spatial and temporal evolution characteristics of drought in Guizhou Province from 1961 to 2015.The main research contents and results of the thesis are summarized as follows:(1)According to the source of monitoring data,drought monitoring methods can be divided into three categories: meteorological monitoring methods,remote sensing monitoring methods and integrated remote sensing monitoring methods.According to the nature of the index,it is divided into meteorological drought index,remote sensing drought index and comprehensive drought index.The meteorological monitoring indicators have the earliest origin and simple calculation.However,based on the data acquired by the site,the data structure is single and requires long time series.The missing or distortion of the site data is a weakness that cannot be ignored.The data source of remote sensing drought index is surface data,with high timeliness and accuracy,but the data processing process is complex and has regional applicability restrictions.Comprehensive monitoring indicators to obtain data through multiple channels,build a multi-indicator model,further improve the applicability and accuracy,and become a new trend in drought monitoring research in the future.(2)In the past 55 years,the degree of drought has increased and the scope of drought has increased.The average percentage of arid area in Guizhou Province is as high as 65%,the average percentage of heavy drought area is 8%,the percentage of large drought area is between 20%and 30%,and the average percentage of drought area is 30%.Heavy drought areas are mainly distributed in the northeast,central and southwestern parts of Guizhou Province,especially in Bijie,Jinsha,Liuzhi,Zhenfeng,Wangmong and Wengan.Among them,the phenomenon of heavy drought was the most serious in 2011,and the area of heavy drought accounted for 26% of the total area of the province.The area with heavy drought has formed a “north-southwest” strip-shaped arid zone from Tongren-Guiyang-Bijie-Liupanshui,and the drought intensity The axis decreases toward the northwest and southeast;(3)Drought intensity decreases with the increase of drought frequency.Drought is widespread in southern Fujian and southwestern Guizhou,and the drought intensity is low,but the frequency of drought is relatively high,up to 29.11%.The main drought occurs in central Yunnan and northern Hebei,and the highest frequency of drought is 25.74%;Heavy drought occurred in southeastern Yunnan,but its frequency was the lowest,with a minimum of 1.26%.(4)The karst areas are mainly affected by severe drought with a probability of 37.63%.Sub-karst areas are more prone to great drought with a probability of 36.56%.Non-karst areas were more prone to partial drought,with a probability of 36.52%.Therefore,both drought intensity and drought frequency have the rule that the karst area is larger than the sub-karst area and the non-karst area.