| In the context of the increasingly prominent global drought problem,the study of regional drought evolution and agricultural disaster damage is crucial to the realization of drought resistance and disaster reduction and sustainable agricultural development.In this thesis,Liaoning Province is selected as the research area,and the inherent relationship between drought and climate is revealed by analyzing the evolution process of regional drought disasters,local extreme climate,and the characteristics of large-scale climate system changes,and the climate influencing factors of drought events are identified.At the same time,based on soil-crop-Atmospheric continuum system,which integrates meteorological stations and remote sensing multi-source data to analyze vegetation,soil,precipitation,temperature and other multi-source drought-related information,and uses the entropy weight method to construct a standardized precipitation evapotranspiration index(SPEI)and crop water deficit index(CWDI)and Temperature Vegetation Drought Index(TVDI)comprehensive agricultural drought risk assessment model to analyze the temporal and spatial evolution characteristics of drought in each growth period of crops in Liaoning Province.Comprehensive agricultural drought index is used for correlation analysis to further clarify the response of crop growth to drought events.On this basis,human factors(production level indicators)are considered to construct a disaster risk index and risk zoning.This research will make up for the shortage of using a single index to assess the risk of agricultural drought disasters,promote the process of comprehensive disaster risk and management research,and provide a theoretical basis for clarifying the mechanism of drought,drought prediction and early warning,and drought relief.The main research conclusions are as follows:(1)Analysis of influencing factors and formation mechanism of drought disasters in Liaoning Province: From the perspective of temporal and spatial distribution,the climate of Liaoning Province has changed from dry to wet in the past 54 years.Spatially,mode 1 shows the consistency of the whole region,and mode 2 shows the reverse distribution pattern of western Liaoning and eastern Liaoning.The joint probability of intensity increases with the increase of duration and intensity value.From the perspective of the causes,drought and flood disasters are prone to occur in the two years around the extreme sunspot number year due to the influence of solar activity;SPEI is negatively correlated with ENSO and NAO,but positively correlated with PDO and AO,and there are different time scales.There is also spatial heterogeneity in the resonance period and its correlation strength.(2)Identification and quantification of drought disasters in spring maize in Liaoning Province based on multi-source data fusion: The maize comprehensive agricultural index IADI constructed from the standardized precipitation evapotranspiration index,water profit and loss index and temperature vegetation drought index has good applicability,and the temporal changes of IADI and MCI index are highly similar.MCI and IADI reached a significant correlation level in most areas;in addition,IADI could accurately identify drought events in different growth stages of spring maize in the study area.(3)Drought characteristics and disaster risk zoning: The high-yielding areas of spring maize are mainly located in northern Liaoning,followed by western and southern Liaoning.The overall growth of spring maize in Liaoning Province is good,and the autumn drought has a greater impact on the yield of spring maize.The IADI value of different growth periods showed an overall upward trend from 2001 to 2019;through the analysis of four disaster risk areas in Liaoning Province,the drought damage degree of spring maize in Liaoning Province during the growth period was from the west,north and east of Liaoning Province to the middle of Liaoning Province.and decreasing in the south. |
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