Contribution of Recycling of Surface Precipitation to Landfalling Tropical Cyclone Rainfall: A Modeling Study for Typhoon Utor (2013)

摘要

Surface evaporation is an important factor in the hydrological cycle. It is unknown however how much the recycling of surface precipitation contributes to rainfall in a landfalling tropical cyclone. In this study, ensemble simulations were performed using the Weather Research and Forecasting model to quantify the contribution of re-evaporation of surface precipitation to rainfall in Typhoon Utor (2013) during and after its landfall over South China. Two sets of ensemble simulations were conducted, one with all default model settings (CTRL) and the other with the surface precipitation rate in the land surface model being set to zero within a radius of 500 km from the storm center so that the re-evaporation of surface precipitation was removed. Results show that the re-evaporation of surface precipitation contributed about 15-20% to the total rainfall in the inner core within a 100-km radius from the storm center after landfall. It is found that the removal of surface precipitation in the land surface model reduced soil moisture and thus surface latent heat flux, which led to a slightly weaker storm, thus the weaker boundary layer inflow and reduced inward moisture transport into the inner-core region of the storm. The results demonstrate that the reduced surface evaporation and inward moisture transport contributed about 30-40 and 60-70%, respectively, to the decrease in precipitation in the inner-core region in the experiment with the reevaporation of surface precipitation removed.