Abstract
Typhoon Hagibis induced massive amounts of rains in eastern Japan. In the down stream of Arakawa basin, the water level reach nearly the inundation bankfull stage. In the future, the inundation risk may increase if a more extreme event than Hagibis strikes the basin. Thus, the increased rainfall data will be necessary as information of evacuation activity. We focused on manipulation of SST (Sea Surface Temperature) because SST takes a role as resource of water vapor which is one of factors for nimbo-developing. This study aims at increasing the rainfall induced by Hagibis and analyzing the impact against change of SST with WRF-ARW model (Weather Research and Forecasting model). Moreover, we validate the reproduction performance for this event to adequately discuss the impact of SST.
As a result, WRF model reasonably reproduced the rainfall compared with radar observation although the calculated hourly rainfall shows some difference in the peak time and amount of rainfall. With respect to impact of SST, we confirmed that change of SST strongly affects the rainfall amount and the peak time. The reasons were as follow: 1) The typhoon tracks for each calculation case show the difference due to change of pressure field. 2) The vapor flux distribution shows that high/low vapor flow into Kanto region. In addition, the mountain terrain located in upstream of Arakawa basin uplift the air mass including moisture.
