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Titre : Assessment of Meteorological Drought Risk in Xinjiang and Its Impact on Agriculture and Vegetation Based on Copula Method

Auteur : 李华伟

Grade : Doctoral Dissertation 2022

Université : North China Electric Power University

Résumé partiel
Global climate change is one of the greatest threats to the earth in the 21st century.Due to climate change,the frequency and severity of extreme events such as droughts and high temperatures are expected to increase further in the future.Drought is a major natural disaster event that can have a significant impact on the ecological environment,water resources,agriculture and other related fields in any region of the world,and has a profound impact in an increasingly globalized world.Xinjiang is one of the main agricultural production bases in China,and it is also a drought-prone area.At the same time,due to the impact of extreme events such as drought and high temperature,the vegetation in Xinjiang has undergone significant changes.Due to serious land desertification,severe evaporation of soil water,coupled with the impact of extreme climate,the overall vegetation ecological environment in Xinjiang is extremely fragile.Therefore,understanding the occurrence and variation of drought events in historical and projected future climates,and assessing the impact of drought on agriculture and vegetation loss are critical for the effective management of natural resources and the development of related policies.Therefore,this study developed a set of risk assessment and quantification method systems based on probability and statistical analysis to reveal the historical drought evolution trends and predict the future drought changes in Xinjiang.Through constructing joint probability distribution functions between the drought index and the agricultural crop yield and vegetation characteristic index,the impacts of drought on crop yield and the vulnerability of vegetation ecosystems are analyzed,which provided important decision support for drought prevention and disaster mitigation in Xinjiang.In details :（1）The characteristics of drought duration,severity and mean time interval are identified based on SPEI（Standardized precipitation evapotranspiration index）using run theory.The joint distribution of drought duration and severity extracted from 66 stations in Xinjiang is constructed based on bivariate copula statistical probability model.Then the drought characteristic risk is evaluated from multiple variables perspectives respectively.The results show that Xinjiang experienced severe drought events in the early 1980s and early 21st century.In terms of the spatial distribution of drought events,the Tarim Basin region in southern Xinjiang,which mainly includes the junction of Hotan Prefecture,Aksu Prefecture and Bayingolin Mongol Autonomous Prefecture,is the area with high incidence of severe drought events.（2）The temporal and spatial patterns of drought characteristic risks under different shared socioeconomic paths（SSPs:SSP126,SSP245,SSP370 and SSP585）in the future are analyzed and identified at grid scale based on the copula function,coupling with CMIP6（Coupled Model Intercomparison Project Phase 6）multi-model ensembles,as well as statistical downscaling and bias correction methods.Results show that the drought risk of high severity and long duration increased gradually in Xinjiang.

Mots clés : risk management ;drought;multiple variables ;compound event ;climate change ;

Présentation (CNKI)