第一届未来大气科学论坛

Previous studies have emphasized the role of the stratospheric Quasi-Biennial Oscillation (QBO) in modulating tropical precipitation. However, the relationship between precipitation and QBO index at different stratospheric levels is inconsistent. This study identifies two distinct vertical structures of tropical stratospheric zonal wind that influence tropical precipitation. When zonal wind at 50 hPa and 70 hPa are westerlies and the upper stratosphere (above 50 hPa) is dominated by easterlies, a positive anomaly in convective stability at the tropical tropopause over the central equatorial Pacific results in a weakened Hadley circulation and reduced precipitation. When westerly winds prevail at 10 hPa while winds between 20 hPa and 70 hPa are easterlies, a negative convective stability anomaly at the tropical tropopause over the Indonesia region drives a westward shift of the Pacific Walker circulation, enhancing upward motion and precipitation in the western equatorial Pacific. The linear combination of time series from these two structures effectively explains a portion of the interannual variability in tropical precipitation after removing the El Niño-Southern Oscillation (ENSO) signal. An evaluation of 15 models from Phase 6 of the Coupled Model Intercomparison Project (CMIP6) shows that eight models accurately reproduce the relationship between wind structures and tropical precipitation. The vertical structure of stratospheric zonal wind exerts a significant influence on tropical precipitation patterns.

QBO,stratosphere-troposphere interaction,tropical precipitation