Satellite observations from Aura Microwave Limb Sounder (MLS) showed that polluted clouds over South-East Asia are associated with higher temperature and water vapor in the tropical tropopause layer (TTL) than clean clouds, although the mechanisms for this aerosol-cloud-water vapor interaction are not well understood. In this study, a set of coupled aerosol-climate model simulations are conducted to identify the radiative and microphysical effects of aerosol on the water vapor near the tropopause, with a focus on Asian pollution. We employ the NCAR Community Atmospheric Model Version 5 (CAM5) with a double moment cloud microphysics scheme coupled to the modal aerosol model. Both homogeneous ice nucleation on sulfate and heterogeneous ice nucleation on mineral dust, and the competition between these two are considered for ice clouds. Two simulations with present-day and preindustrial aerosol and precursor emission scenarios are conducted. We find that increasing aerosol leads to increased temperature and water vapor in the upper troposphere and lower stratosphere, especially over Asia. A sensitivity model experiment with the radiative effect of black carbon suppressed suggests that the radiative heating of black carbon makes primary contribution to the TTL warming and moistening, while upper tropospheric ice cloud changes due to the aerosol microphysical effect also impact the water vapor near the tropopause.