Influence of the strongest central Pacific El Nino-Southern Oscillation events on the precipitation in eastern China

摘要

The impact of the strongest central Pacific (CP) El Nino event 2009/2010 and CP La Nina event 1998/1999 from 1979 to 2010 on the precipitation in eastern China has been analysed. During the 2009/2010 CP El Nino event, it is rainy in northern China during maturing winter and decaying spring, but dry during decaying summer. The rainfall centre is located in south China during maturing period and gradually moves northwards, remaining over the Yellow-Huai River valley during decaying summer. When the 1998/1999 CP La Nina event occurs, northern China is in a state of drought throughout. In south China, dry periods gradually evolve into rainy ones from maturing winter to decaying summer. The two strongest events also have notable impact on the extreme rainfall, and they mainly affect the total rainfall by influencing the extreme precipitation in eastern China. When the 2009/2010 CP El Nino event occurs, the Western Pacific Subtropical High (WPSH) is stronger with a northwards shift, and there is an obvious anticyclonic circulation near the South China Sea and Philippines. Furthermore, during decaying summer, the Pacific-Japan (PJ) wave train shows an eastwards shift comparing to the typical PJ wave train locating from low latitudes to high latitudes, associating with clearly northwardly spreading wave activity fluxes (WAFs) from the equator. When the 1998/1999 CP La Nina event occurs, the WPSH is weaker and retreats eastwards, and there is a noticeable cyclonic circulation around the South China Sea. In decaying spring, the convective activity in the South China Sea is strong, and there are correspondingly significant WAFs spreading from southeastern Asia to north. In decaying summer, northern (southern) China is controlled by anomalous anticyclones (cyclones) with weak (strong) convection, and the WAFs extend northwards to the Yangtze and Huai River valleys.