Contribution of Surface Precipitation Evaporation to Landfalling Typhoon Rainfall: A Modeling Study of Typhoon Utor (2013)

Surface evaporation was an important factor in typhoon evolution upon landfall. But how important is the surface precipitation evaporation to landfalling typhoon rainfall? In this study, numerical experiments and numerical ensembles were performed using the Weather Research and Forecasting (WRF) model to quantificationally examining the contribution of surface precipitation evaporation to landfalling typhoon rainfall. The results showed that the decay of typhoon precipitation in control experiment (CTL) was slower than that in sensitive numerical experiment (No_evap) due to the cutoff of the surface precipitation evaporation. In inner-core region of Typhoon (within radius of 100 km), the precipitation in No_evap was weaker than that in CTL when the storm moved inland. The averaged contribution of surface precipitation evaporation accounted for about 10% in the inner core of storm after landfall, which was much higher than that in the entire storm precipitation with contribution of only 3% - 5%. The surface precipitation evaporation cutoff directly influenced the soil moisture, the surface latent heat flux and the low-level atmospheric environment during and after the landfall of typhoon, which provided less energy for landfall typhoon. The analysis of the water budget indicated that the change of vertical water vapor flux was the primary reason for water vapor mixing ratio decreased in storm over land, consequently causing total precipitation decreased.