Effect of land cover pattern on rainfall during a landfalling typhoon: A simulation of Typhoon Hato

Abstract

The impact of urbanization on weather events has received increasing attention. Taking Typhoon Hato as an example, the impact of anthropogenic land cover change on typhoon landfall and sequential rainfall is quantified in this study. A numerical model is first built based on the Weather Research and Forecast model. Then, the model is validated, the performance of parameters for the different meteorological and microphysical processes is assessed and a set of optimal parameters are selected. After that, the responses of typhoon and the corresponding rainfall to land cover patterns under three conditions of no urbanization, current urbanization and future urbanization in Pearl River Delta are simulated and compared. Verification experiments show that it is necessary to consider the microphysical process to enhance the accuracy of typhoon simulation. The dramatic change of land cover has limited influence on typhoon tracks. However, the urbanized land surface promotes typhoon rainfall significantly. The hourly rainfall rate under the urbanization condition is about double that under the no urbanization condition. With the intensifying urbanization in the future, the maximum hourly rainfall rate will increase by 21%. The urban heat island effect almost disappears as Typhoon Hato approaches the inland region, and the urban dynamic effect plays an important role in typhoon rainfall. The intensified rainfall is related to the retention of typhoon caused by rough surface of the city. The wind speed under the condition of no urbanization is in general 2 m/s greater than that under the urbanization condition. The increase in surface roughness reduces the typhoon movement speed and more rainfall is generated. With the development of urbanization, intensified rainfall at typhoon landfall needs to be paid more attention to.