Evaluations of Prior Potential Predictors for the Summer Rainfall in the Middle and Lower Reaches of the Yangtze River
影响长江中下游夏季降水的前期潜在预报因子评估

In the framework of impacts of sea-land-atmosphere factors on the following summer rainfall in the middle and lower reaches of the Yangtze River (MLYR), the authors reconstructed 40 factors on the basis of sea surface temperature (SST), snow depth in the Tibetan Plateau, and NCEP/NCAR reanalysis datasets, and evaluated their possible impacts on the summer rainfall in the MLYR. Firstly, the authors discussed the stability of relationships between these factors and the following summer rainfall in the MLYR before and after 1979. Secondly, the authors selected several important factors by correlation analysis, and discussed the relationship between these factors and East Asian summer monsoon (EASM). In addition, the potential forecast capability of these factors for the summer rainfall in the MLYR was discussed by historical hindcasts. The results suggest that the important winter predictors for the summer rainfall in the MLYR mainly come from the external forcing, such as the SST in Ni o3 and Kuroshio Current regions, and the snow depth in Tibetan Plateau. In contrast, the potential spring predictors are almost the general circulation indices, such as Arctic Oscillation (AO), polar vortex, and the western North Pacific subtropical high (WNPSH). Running correlations between these potential predictors and the summer rainfall in the MLYR vary on interdecadal time scale, however, the SST in Kuroshio Current region, the snow depth in the Tibetan Plateau, and the surface air temperature near Lake Baikal show the significant antecedents for summer rainfall in the MLYR by affecting the EASM circulations, and jointly suggest the better forecast capability for the rainfall anomaly in the MLYR after 1979.