The Variation Of Autumn Rainfall In Southeast China And Its Association With Sea Surface Temperature In The Trorpical Pacific Sea

Southeast China is adjacent to the South China Sea southward,and is close to northwest Pacific eastward,in which the precipitation is obviously different from other parts of China in autumn,and that accompanied by the characteristics of multi-scale variations.In Southeast China,the economy is rich,but autumn droughts occurred frequently in recent years,which severely threatens people's life and property safety.Therefore,finding out the characteristics and causes of the autumn precipitation variation has very important practical significance for disaster prevention and allleviation.In this paper,the station precipitation data,JRA55 reanalysis data and Hadley center SST data etc.,and that the composite analysis,empirical orthogonal function decomposition(EOF),linear regression analysis and dynamic diagnosis were used to discuss the spatio-temporal variations of rainfall in Southeastern China and its connection with tropical pacific SST.Main conclusions are as followed:(1)The relative drought in Southeastern China in autumn mainly associated to the climate circulation condition.The low-mid tropospheres in southeastern China was controlled by anticyclonic circulation,in which water vapor is divergent,and the sinking motion prevails.(2)The rainfall in the studied region showed multi-scale characteristics.After 1990,the precipitation of Southeastern China jumps to be less,which is associated with the decadal warming of SST in the tropical central Pacific,The inter-decadal increase of SST in the tropical central Pacific made the atmosphere generate Gill response,at the same time exciting low-troposphere anomalous cyclone over the Northwestern Pacific.Its peripheral airflows transport the water vapor from south to north more weakly,resulting in the reduction in the precipitation after 1990.Those statistical results can be confirmed by the sensitive experiments of ECHAM5.In addition,it also showed significant inter-annual changes.In the less-rainfall years,a anomalous cyclone appeared in the South Sea and northwest Pacific,and its strength weakened accompanied by height in the troposphere.Its peripheral airflow from north to south to transport water and cold advection to southeast China,and therefore generated lower temperature and geopotential height in the studied region.Meanwhile,this area was controlled by the anomalous circulation in the subsidence,and rapid mixing ratio is negative anomaly,not conducive to the occurrence of precipitation.In more rainfall years,a abnormal cyclone was observed in the South Sea and west Pacific,in which its peripheral airflow from the south to the north transported to the southeast China.The arid regions of southeast in the fall is abnormal,the abnormal warm advection and rapid mixing ratio were facilitated to the occurrence of precipitation.Further research indicated that two major mode of inter-annual precipitation was observed in the Southeastern China,which was consistent mode and dipole mode,respectively,and that which was well associated to the EP ENSO and CPENSO,respectively.(3)Around 1990,The relationship between SST and precipitation in southeast China showed inter-annual changes.Because EP El Nino was advantageous to increase the autumn rainfall and CP El Nino was advantageous to decrease the autumn rainfall in Southeastern China,and it was shifted to the contrary after 1990,resulting rainfall anomaly frequency change in Southeastern China,and thus causing the change of annual fluctuations.