The Influence Of The Silk Road Teleconnection Pattern On The Summer Heavy Precipitation In East China

With the deteriorating and warming global climate,extreme weather processes frequently occur around the world,which have a serious impact on social development and ecological environment.Among them,the occurrence of heavy precipitation will not only cause serious flood disasters,but also threaten the safety of human life and property and cause huge social and economic losses.However,my country is in the East Asian monsoon region,which is prone to heavy rainfall in summer,and its occurrence is affected by a variety of key weather systems.Among them,the Silk Road teleconnection Pattern(SR pattern),as a very important mode over Eurasia,has a key impact on the weather in East Asia.Therefore,this thesis intends to analyze the statistical characteristics of summer precipitation in East China under the influence of SR type from the perspective of SR type on a daily scale,and explore its impact on summer heavy rainfall in East China.The key circulation factors of precipitation,and the relevant conclusions are of great reference value for the impact of heavy precipitation on civil aviation flight safety in East China.This thesis is based on the daily precipitation data of"China's daily ground precipitation0.5°×0.5°grid data set(V2.0)"provided by the China Meteorological Data Service Network of the National Meteorological Information Center,NCEP/NCAR daily reanalysis data,and the European Center The daily reanalysis data provided by ERA5(ECMWF),firstly define the typical positive(negative)events of the Silk Road teleconnection during the summer of1979-2015(June-August),and calculate the daily Silk Road Index(SRI)and The East China Precipitation Index(I_RAIN),based on the index,selects typical SR-type positive and negative events,reveals the possible connection between the Silk Road type and heavy rainfall in East China through synthetic analysis,and clarifies the Silk Road teleconnection model.Distribution pattern and spatiotemporal distribution characteristics of heavy precipitation in East China.The study found that during the typical SR-type negative event,there was an obvious heavy precipitation process in East China,but during the SR-type positive event,there was no heavy precipitation signal in East China.Secondly,this thesis conducts a synthetic analysis of the geopotential height field,low-level wind field and water vapor flux,low-level wind field,outward long-wave radiation and wave action flux during the SR type positive(negative)event,and further analyzes the possible causes of the SR type and its effect on heavy precipitation in East China.The results show that during the SR-type positive event,the water vapor conditions over East China are relatively weak,the southwest warm and humid water vapor brought by the Bay of Bengal is concentrated in the southwest and southeast coasts of my country,and the contour lines in the middle and high latitudes are relatively straight,making the middle and high latitudes relatively straight.The dry and cold air at high latitudes cannot go south to East China to join the warm and humid air flow in the southwest,which is not conducive to the occurrence of precipitation,so there is no obvious precipitation signal in East China.During the occurrence of the SR-type negative event,the convective activity in the upper Black Sea area of Eurasia was abnormally strong,which stimulated the wave action flux along the westerly jet at the upper level,in addition,there is a significant wave energy convergence in East China,prompting the emergence of low pressure troughs in the mid-latitudes of East Asia.At the same time,the large-scale circulation background of"troughs,ridges,and troughs"in the middle troposphere is also favorable for wave activity to disperse energy downstream.In the lower troposphere,with the action of the Somali cross-equatorial airflow,a large amount of water vapor is transported from the Indian Ocean to East China through the Arabian Sea,the Bay of Bengal and the South my country Sea.At the same time,the ridge line of the Western Pacific Subtropical High(WPSH)extends westward to the west of 120°E,and the southeastern airflow on its south side can also bring some water vapor over the Pacific to East China,and the mid-latitude regions of East Asia.There is a significant low-pressure trough,and the South Asia High(SAH)extends eastward to 120°E,and the northerly airflow on its northeast side deepens the mid-latitude low-pressure trough.The dry and cold air from the middle and high latitudes descends southward to East China,where it meets the warm and humid water vapor from the southwest,which is conducive to the occurrence of obvious heavy precipitation in East China.Finally,through the comparative analysis of typical SR-type positive and negative event cases,as well as typical SR-type"dry"and"wet"events,it is found that typical positive events are similar to"dry"events in negative events.The weaker water vapor and the dry and cold air in the middle and high latitudes did not move southward,making East China unsatisfactory for the conditions for heavy precipitation.In typical negative events,the situation of"wet"events is the opposite.Due to the control of high-level SANs,there is a strong divergence over East China.The convergence of dry and cold air in the south of the latitude,East China meets the mechanism that can produce precipitation,resulting in an obvious heavy precipitation process in East China.