Quasi-Biweekly Oscillation of the South Asian High and Its Role in Connecting the Indian and East Asian Summer Rainfalls

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.

Duke Scholars

Author Wenhong Li Earth and Climate Sciences