Gravity wave analysis and stratosphere-troposphere exchange during Typhoon Molave (2020)

To investigate the stratosphere-troposphere exchange (STE) process induced by the gravity waves caused by typhoon “Molave” (2020) in the upper troposphere and lower stratosphere region, we analyzed the ERA5 reanalysis data provided by European Centre for Medium-Range Weather Forecasts and the tropical meteorological optimal path dataset from China Meteorological Administration. We also adopted the mesoscale forecast model Weather Research and Forecasting model, V4.3, for numerical simulation. Most of the study is about typhoon-induced STE and typhoon-induced gravity waves, so our research will provide information for the study of STE caused by typhoon-induced gravity wave breaking. Our analysis shows that in most of the time, the gravity wave signal of typhoon “Molave” appeared below the tropopause and on the east side of the typhoon center (10°N-20°N, 110°E-120°E), it was stronger than that on the west side, suggesting an eastward tilted structure with height increase. When the gravity waves in the UTLS region (100°E-108°E) which on the west side of the typhoon center broke up, it produced strong turbulent, resulting in stratosphere-troposphere exchange. At this time, \(\stackrel{-}{PVW}\), the average potential vorticity vertical flux, increased with the average ozone mass mixing ratio. The gravity wave events and STE process simulated by the WRF model are basically consistent with the results of ERA5 reanalysis data, but the time of gravity wave breaking is different. This study indicates that the distribution of typhoon-induced gravity waves is related to the background wind field, and after it is broken, it will generate turbulent mixing, causing the STE.