Hindcast of Typhoon Jongdari and Non-Tidal Sea Level Residuals in Mikawa Bay Using Fdda in WRF

Abstract

Numerical simulation of the storm surge by an unexpected typhoon and the elucidation of the mechanism of its occurrence are indispensable for improving disaster prevention measures in coastal area. Reproducibility of meteorological fields such as wind speed and atmospheric pressure by a typhoon is important for estimating storm surge. For improving the reproducibility, four-dimensional data assimilation (FDDA) is applied in Regional Climate Model. Numerical simulation of storm surges caused by typhoons, for examples, Isewan Typhoon that caused enormous damages in coastal area of Ise and Mikawa Bays in 1965, has been carried out, and the mechanism of its occurrence also has been investigated by many researchers so far. Typhoon Jongdari in 2018 approached to the mainland of Japan. However, its track was from east to west, which is an opposite direction of the typical typhoon track around Japan. The effectiveness of FDDA on the hindcast of Typhoon Jongdari and the reproduction of anormal water level deviation in Mikawa Bay were evaluated using atmospheric model, WRF, and ocean flow model, FVCOM. The lowest atmospheric pressure, the maximum wind speed and the sea level departure by storm surge were analyzed. The spectrum nudging in WRF demonstrated the results with higher accuracy than those by grid nudging or no nudging.