Most of the lower stratospheric water vapor comes from the tropical troposphere, determined by the cold tropopause temperature over the Indo-Pacific warm pool (IPWP). Previous studies that quantified the relative role of transport processes have generally assumed well-mixed tropics and focused on tropical-wide average characteristics. However, it has recently been shown that there is a hemispheric difference in tracer transport into the stratosphere, highlighting the importance in depicting the hemispheric contrast. Using idealized simulations with WACCM4, we show that the amplitude of the lower stratospheric water vapor in response to a warmer/cooler IPWP in the northern tropics (NT) is larger than that in the southern tropics (ST). But the seasonal evolution is different during the warm episodes and cold episodes: the stratospheric water vapor in NT becomes significantly larger than that in ST in boreal summer in case of a warmer IPWP, while in case of a cooler IPWP the hemispheric contrast occurs in boreal fall to winter. In addition, the seasonality of the stratospheric water vapor transport in the NT is larger than that in the ST. Transformed Eulerian Mean analysis of WACCM4 simulations shows that seasonality in the Brewer Dobson circulation induced by the IPWP drives the seasonality in the stratospheric water vapor, with a large increase in horizontal mixing during boreal summer associated with.