Mechanisms of the transport height of water vapor by tropical cyclones on heavy rainfall

The moisture transport by tropical cyclones is characterized by high intensity and altitude, which may affect the microphysical processes of heavy rainfall triggered by tropical cyclones. In this study, we used the Weather Research and Forecasting (WRF) model to conduct numerical simulations on a heavy rainfall event near the Yangtze River Delta induced by Super Typhoon Mangkhut (2018). The vertical distribution of water vapor was modified to highlight the impact of moisture transport at various heights. The results showed that the distribution and intensity of the rainfall event changed with the transport height of water vapor. Ensuring that the water vapor content in the column kept constant, the total amount of precipitation in the region was greatest when the transport occurred primarily at low levels, and smallest when the transport occurred primarily at midlevels. Detailed analysis of cloud water, rainwater, and frozen hydrometeors showed that liquid- (ice-) phase processes were the dominant microphysical processes when the transport height is low (mid-to-low). The deposition and riming processes contributed to heavy precipitation when the transport height was at the mid-toupper levels. Our findings underscore the influence of moisture transport with high intensities and altitudes by tropical cyclones on microphysical processes, ultimately leading to changes in the distribution and intensity of heavy rainfall. Therefore, when analyzing heavy precipitation events, particular attention should be given to the moisture transport at the mid-to-upper levels.