First, the annual mean NT-ST differences at lower stratosphere (80 hPa) in response to IPWP Niño/Niña based on WACCM4 simulations are shown in Table 1 . The experimental design is described in section 2. Coherent with \citet{Xie_2018}, the IPWP Niño events tend to dry the tropical lower stratosphere with negative stratospheric water vapour anomalies in both NT and ST, and vice versa for IPWP Niña. The amplitude of the water vapour response, however, is about two times larger in NT than that in ST during both IPWP Niño and IPWP Niña.