资源环境科技发展态势分析平台

Investigation into the intraseasonal variation of the South Asian high (SAH) and its relationship with the Indian and East Asian summer monsoon rainfalls indicates that the 10-20 day period dominates the subseasonal zonal oscillation of the SAH between the Iranian mode and the Tibetan mode. The eastward shift of SAH lags a rainfall decrease over northern India by about 1 day, but leads a rainfall increase over the Yangtze River valley (YRV) by about 3 days. Interactive processes are also revealed on quasi-biweekly time scales. The latent heating over northern India contributes to the southwestward shift of a pair of cyclone-anticyclone anomalies from the midlatitudes to the SAH region, resulting in the zonal shift of the SAH. An associated upper-level divergence over eastern China leads to the rainfall increase over the YRV 3 days later. The lead-lag relationships revealed may benefit the subseasonal rainfall prediction over the two monsoon regions.