Joint effect of East Asia–Pacific and Scandinavian teleconnections on summer precipitation in Southwest China

AbstractBased on the summer precipitation data from 328 meteorological stations in Southwest China and the monthly mean reanalysis data from the National Centers for Environmental Prediction/National Center for Atmospheric Research, the relationships of summer precipitation in Southwest China with the East Asia–Pacific (EAP) teleconnection pattern and the Scandinavian (SCA) teleconnection pattern are explored by using correlation analysis and composite analysis. The results show that the two teleconnections are significantly negatively correlated with the summer precipitation in Southwest China in the same period. The EAP teleconnection pattern and the SCA teleconnection pattern can affect the summer precipitation in Southwest China by affecting the atmospheric circulation situation in the middle and high latitudes, the north–south and east–west movement of the WPSH, and the water vapor transport in southwest China. In particular, the EAP and SCA teleconnections jointly affect the summer precipitation in Southwest China, which can be divided into four categories of configurations based on their phases, that is, (I) positive EAP + positive SCA, (II) negative EAP + negative SCA, (III) positive EAP + negative SCA, and (IV) negative EAP + positive SCA. The distribution of summer precipitation in Southwest China varies under different categories of configurations. Category I (II) corresponds to an opposite distribution pattern of precipitation anomalies between the north and south of Southwest China. In the configuration of category I(II), the cold air from high latitudes is weaker (stronger), the WPSH is more north(south) and more west(east) than the climatological mean, and the water vapor mainly comes from the Western Pacific (Bay of Bengal), thus resulting in category I(II), the opposite distribution of precipitation. While for configuration of category III(IV), no similar symmetrical distribution of precipitation anomalies can be found, and no obvious other distribution characteristics as well.