Now we have confirmed a good performance of WACCM4 in simulating zonal variance of the tropical stratospheric water vapor, and shown the necessarity in dipicting the hemispheric contrast. Next we examine the hemispheric difference of the lower stratospheric water vapor response to IPWP Niño/Niña events, which have already been shown to have significant effects on the entry of water vapour from tropical troposphere to the stratosphere \citet{Xie_2018}. The annual mean tropical stratospheric water vapor is revisited here to further show the hemispheric contrast.