Roles of tropical overshooting convection in variation of stratospheric water vapor: A numerical study using the WRF Model

We simulate overshooting convection in the tropics and analyze its role in water vapor variation in the lower stratosphere using the Advanced Research Weather Research and Forecasting (ARW) model. The overshooting convection is a deep convection that penetrates into the stratosphere. We make a numerical experiment based on an observation, which suggested that the overshooting convection can increase water vapor in the lower stratosphere. A simulation with three nested domains is run for 18 hours; the horizontal grid spacing in the parent domain is 27 km and that in the third domain is 3 km. The vertical domain from the surface to 50 hPa is divided into 80 layers and the vertical resolution near the tropopause is approximately 300m. Initial and boundary conditions are given by Final Operational Global Analysis data (FNL) of the National Centers for Environmental Prediction (NCEP). The WRF model reproduce a number of overshooting convections particularly in the region between 165 and 166E and between 5 and 7S. Temporal variations of specific humidity averaged over that region suggest its increase in the lower stratosphere. To estimate the possibility of its constant increase, however, a long-term simulation is desired.