资源环境科技发展态势分析平台

Using monthly precipitation data and the NCEP/NCAR reanalysis dataset, the salient differences in Chinese summer rainfall in response to moderate eastern/central Pacific El Nino (MEPE/MCPE), extreme strong El Nino (SE), and moderate eastern/central Pacific La Nina (MEPL/MCPL) events are investigated. The distribution of Chinese summer rainfall anomalies varies with the phases, intensities and flavors (i.e. eastern/central Pacific patterns) of El Nino-Southern Oscillation (ENSO) events through the general circulation change. On average, the correlation between ENSO and Chinese summer rainfall anomaly is positive in the Yellow River valley and the middle reaches of the Yangtze River, but is negative in East China, part of Northeast China, and South China. The western Pacific subtropical high (WPSH) extends westward and the South Asian High (SAH) extends eastward during the MCPE and SE decaying summers, leading to enhanced upwelling motions and strong water vapor convergence over the Yangtze River valley. As a result, positive rainfall anomalies appear in this region. In contrast, no significant rainfall anomalies form along the Yangtze River valley during the MEPE decaying summer. During La Nina decaying summers and especially the MEPL decaying summer, both the WPSH and SAH shrink. The rainfall anomalies during the MEPL decaying summer exhibit a dipole pattern: dry (wet) to the north (south) of the Yangtze River. However, patches of significant negative rainfall anomalies appear during the MCPL decaying summer. As the maximum SST anomaly center shifts between different ENSO flavors, the anomalous anticyclone/cyclone in the western North Pacific also sways in its zonal position.