Abstract:Based on the rainfall data of the middle and lower reaches of the Yangtze River (MLRYR) during Meiyu season (MYS), NCEP/NCAR daily reanalysis data, NOAA monthly average sea surface temperature (SST) and Arctic sea ice (ASI) indices data, the circulation characteristics and precursory signals of the abnormal rainfall in MLRYR after 2000 are studied by correlation analysis, regression analysis and other methods. A prediction model is established and a prediction experiment is carried out. The results show that when there is more precipitation in MLRYR, the low-value systems near Balkhash Lake and Bohai Bay in the Eurasian mid-latitudes are more active, the upper-level westerly jet stream is southward and eastward, the low-level wind field is distributed in meridional wave train, the East Asian summer monsoon is weaker, and the Meiyu front is strong in the area from the Sea of Japan to MLRYR, which results in strong ascending motion and convergence of water vapor flux over MLRYR, thus increasing the rainfall therein. The anomalous SST over tropical eastern Pacific (TEP) and ASI in previous winter are the main precursors of abnormal Meiyu rainfall over MLRYR. The anomalous anticyclone over South China Sea during MYS induced by the positive phase of SST over TEP and ASI are beneficial to the convergence of cold air and warm moist air over MLRYR. So that the rainfall over MLRYR increases. Therefore, the rainfall multiple regression prediction model constructed by the use of SST and ASI factors for MLRYR during MYS can produce better results of fitting and prediction.