An Observational Study on the Latitudes Where Wave Forcing Drives Brewer-Dobson Upwelling

The 40-yr ECMWF Re-Analysis (ERA-40) data are analyzed to demonstrate that wave forcing at lower latitudes plays a crucial role in driving the tropical upwelling portion of the Brewer‐Dobson circulation. It is shown that subtropical wave forcing is correlated with tropical upwelling on both intraseasonal and interannual time scales when transient waves are taken into account, and that tropical wave forcing exerts its influence on tropical upwelling via its body force on the zonal mean flow.