Development of Efficient Technique to Hindcast Typhoons and Associated Waves using Numerical Weather Model

Abstract

For the prevention of coastal inundations, numerical simulations of storm surges and waves based on the wind information of typhoons are indispensable. The wind field induced by typhoons were generally calculated using so-called parameter models. The parameter models are easy to use. However, it cannot take into account the interaction between the wind and the topographical terrain. In this study an efficient technique is developed to hindcast the wind fields for the past typhoon events. The WRF-ARW model is employed. The vortex components of wind field are first removed from the global data, and an artificial typhoon corresponding to the best-track data is obtained using the TC-bogus routine implemented in the WRF-ARW model, and is prescribed along with the typhoon track. The WRF-ARW run is conducted with the spectral nudging activated. In general, the wind field obtained in this way is much weaker than that of a real typhoon. Thus, an iterative technique is developed. The improved wind field obtained from the first WRF-ARW run is employed as an input wind field for the succeeding WRF-ARW run. The iteration is repeated until a satisfactory result is obtained. The calculated wind fields and associated wave fields are compared with the data measured at several buoy stations. Good agreement is achieved. The improved wind field can serve as a useful tool to simulate the coastal inundations for the design of coastal defense works.