The roles of the Hadley circulation and downward control in tropical upwelling

The magnitude and configuration of tropical upwelling of tropospheric air into the stratosphere plays an important role in determining tropical tropopause properties and in stratosphere-troposphere exchange. It is likely of great importance in understanding observed variations in stratospheric water vapor. Here, we present several idealized models of tropical upwelling, which clarify the roles of the nonlinear Hadley circulation and extratropical wave driving in determining the circulation. In particular, we show that the Hadley circulation and wave-driven circulation interact to determine the nature of tropical upwelling. We are able to explain several observed features such as maximum upwelling in the summer hemisphere and the annual variation of the upwelling.