Study On The Characteristics And Causes Of The Abnormal Climate Changes Of Rainstorm In Guangxi

Located in the western part of southern China,Guangxi has a unique terrain and unique climatic characteristics.It is a frequent area of heavy rain in China.Every year,floods caused by heavy rains cause serious economic losses and casualties in Guangxi.Currently,There are still many important issues in the climate change and its abnormal causes of heavy rain in Guangxi that have not yet been studied clearly.Therefore,it is very important to study the characteristics of the multi-scale variation of heavy rain in Guangxi and its causes,to deepen the understanding of the physical mechanisms of frequent heavy rain events,and to improve the prediction level of flood disasters in Guangxi and to prevent and mitigate disasters.In this paper,using the daily precipitation data from the surface meteorological observatory in Guangxi from 1961 to 2016,using statistical diagnostic methods,the interannual and interdecadal variations of the rainstorm in Guangxi,regional,correlation,and climatic characteristics were analyzed,and the non-uniformity during the rainstorm year was studied.Response of wide range of heavy rains in Guangxi to the interdecadal oscillation of the Pacific Sea surface temperature(PDO),and the anomalous changes of atmospheric circulation in wide range of heavy rains were studied,to reveal the anomalous characteristics of climate change in Guangxi and its causes.The main conclusions are as follows:It reveals the new characteristics of climate change in Guangxi rainstorm: The three rainstorm centers in the northeastern part of Guangxi,centered on the northern part of Liuzhou City,and the western part of Guangxi,centered on the “Dongbafeng”,and Coastal area,are the large-value areas with heavy rain and rainfall as a percentage of total precipitation,and highly concentrated in heavy rain.In summer,northern of Guilin and Liuzhou are areas with high frequency of heavy rains.The number of heavy rains and wide range of heavy rains in Guangxi have obvious interdecadal variations and show a significant increase trend,especially the trend of wide range of heavy rains in the northeastern and southeastern of Guangxi in summer,and in Hezhou-Southeast of Guangxi in autumn.The number of heavy rain days is the least in the 1970 s.In the 1990 s and 2000 s,there were significant mutations from 1983 to the end.In the mid-1980 s,the interannual anomalies of persistent heavy rains in the Guangxi region increased,and in 1989 and 2011,they were unusually small,1994 and 2008,there are a lot of abnormalities.It reveals the relationship between the heavy rain in Guangxi and the Tibetan Plateau ground heating and PDO.In the early winter,the surface heating intensity of the Qinghai-Tibet Plateau is weak.In the summer,the high-altitude rising speed in the eastern Qinghai-Tibet Plateau is weakened,the sinking airflow over the Central Pacific Ocean is enhanced,and the subtropical high pressure and the Baikal Lake block high pressure intensity are strong,which is conducive to water vapor,unstable energy transport to Guangxi and cold air to Guangxi,the southern equatorial south wind is stronger in Australia,and the southerly wind is weak in the mainland,the rain belts in the flood season in China are southerly,which are conducive to the concentration of heavy rain in Guangxi.The PDO is in the cold phase,the ridge fluctuations and the constant wave intensity increases in the high latitude area,the Baikal lake block high pressure intensity is stronger,the mid-latitude constant wave intensity is weakened,the western Pacific subtropical high is stronger,the ridge line is northerly,and the west ridge point is west.The vertical shear of the upper equatorial wind in the western equatorial Pacific is enhanced.The high pressure in Australia is strong,and the equatorial airflow in Somalia is significantly enhanced.The upper reaches of the northeast coast of New Guinea Island is an anticyclonic circulation,and the cyclone circulation over the southeastern part of the Philippines.The anti-cyclonic circulation over the northeastern part of the Philippines and the cyclone circulation of Guangxi to the coastal areas of southern China have caused a large number of heavy rains in Guangxi.The heavy rains in Guangxi are significantly affected by the onset time of the South China Sea summer monsoon and the tropical seasonal oscillation(MJO).The South China Sea summer monsoon erupted earlier,and the high altitude temperature from the South China Sea to the eastern part of China and the Central South Peninsula to central China early changed from "northern and cold south" in winter to "northern and cold south" in summer.The location of the 850 h Pa north-south winds in central China has obvious fluctuations with the seasons.The southernmost part of the north wind in the front flood season is southward,resulting in a large concentration of heavy rain in Guangxi.From May to July,the MJO moved eastward and reached the area east of the Philippines or near the island of New Guinea.It formed a wave that spread to the northwest and passed through the South China Sea to Guangxi,causing frequent rainstorms in Guangxi.When MJO is located in the Western Pacific-Malaysia maritime continent,the frequency of tropical cyclones affecting Guangxi and the number of rainstorm days are excessive.