Time-space Evolution And Joint Probability Analysis Of Regional Meteorological Drought Events

Affected by global climate change,meteorological and hydrological factors around the world are undergoing significant changes,and their changes have exceeded the natural fluctuations of the Earth itself,resulting in a significant increase in the frequency of drought events,deterioration in duration and severity.In the past,drought research often used single station as the research object,and it is difficult to comprehensively characterize the regional and long-term complex natural disasters such as drought.Therefore,it is necessary to identify regional drought events by method of regional drought event identification,and to study the spatial and temporal distribution law and evaluate the drought risk.It is of great significance to enhance the ability of disaster prevention and mitigation in the study area and to ensure economic,social and natural ecological security.This paper identifies 179 regional meteorological drought events in the study area from 1961 to 2015 by using the method of regional meteorological drought event identification.On this basis,we extract a number of indicators from three aspects: duration,influence area and strength.Their temporal and spatial changes are analyzed,and a comprehensive drought indicator is constructed to comprehensively measure the severity of regional drought events.The ES method was used to construct a complex network of drought events,and three indicators of propagation strength,propagation direction and propagation distance were constructed to measure the overall propagation characteristics of regional drought events.Multi-dimensional Copula function was used to conduct joint probability analysis of regional drought event duration,influence area and strength,and to assess the drought risk in the study area.The main research results of this paper are as follows:(1)The regional meteorological drought event recognition method adopted in this paper can better identify the drought events in the study area,and comprehensively extract the indicators such as the duration,influence area,strength,and daily event center.(2)179 regional meteorological drought events were identified in the study area from 1961 to 2015.The duration,area affected by meteorological drought and the intensity of cumulative process increased in the whole study area,which tended to be serious in general since the 1990 s.(3)The drought events in the middle and southern regions of the study area are more likely to spread outward,and the drought events in the central and western regions are more likely to be affected by drought events in other regions.Shanxi and Henan are the convergence area of drought events,while Anhui and Jiangsu,are the source areas of drought events.(4)The dominant position of drought transmission in the study area has obvious regional characteristics.The central and western regions are more susceptible to the influence of drought events in the western regions,while other regions are more likely to spread drought events to the inside world.Most of the nodes in the study area are closely connected and have a long drought transmission distance.The transmission distance of the nodes in the southwestern edge of the study area is not high,and the area is more likely to be affected by the drought events nearby.(5)Drought events lasting for 100-200 days,with 50% of the affected area and severe drought,and drought events lasting for 100 days or so,with 75% of the affected area and severe drought,have high risk,which should be paid attention to.