Abstract:

Based on the National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data and the precipitation data from 160 stations in China，the relationship and influence mechanism between the Indian Ocean sea surface temperature (SST) in winter and Chinese 160station rainfalls during the next spring are investigated.The empirical orthogonal function analysis results show that the spatial distributions of winter SST anomalies (SSTA) in the Southern Indian Ocean are characterized by monopole with the same anomalous signs in basinscale and by dipole with the reverse signs in the western and eastern Southern Indian Ocean.The second time series of the dipole mode are defined as Southern Indian Ocean dipole (SIOD) index.When the areaaveraged SST anomalies are positive in West Pole and negative in East Pole，a positive SIOD happens.While the areaaveraged SST anomalies are negative in West Pole and positive in East Pole，a negative SIOD happens.The impact of SIOD on the rainfalls in the next spring in China is greatest.In positive SIOD years，the rainfalls are subdued over the Yangtze River and its north in the next spring.While in negative SIOD years，the rainfalls increase over the Yangtze River and its north in the next spring.The relationship is independent of ENSO events.Based on the reanalysis data，using synthesis and related method，we find that SIOD influence on the spring rainfall in China through the joint action of high latitudes and low latitudes.SIOD induces low latitude sea surface temperature and convection anomalies.Through interaction between middle and low latitudes，the anomalies cause strong remote response in the middle and high latitudes，thus affect the same period of circulation changes in winter Eurasia.By the effect of the westerly flow，such perturbations cause the anomalous convective activity in the North Pacific in the next spring.Also through interaction between middle and low latitudes，it strengthens the remote response of the middle and high latitudes，and EUP wave train happens.The convection anomalies in the South China Sea and Sea Maritime Continent caused by SIOD，induce meridional circulation anomalies and vertical motion abnormalities over the Yellow River to the Yangtze River region.Under the joint action of high latitudes and low latitudes，the abnormal rainfall in China happens