Ocean initialization for the typhoon forecast with 3-

Abstract

The ocean state is recently regarded as one of the mostimportant components to determine properties of the tropicalcyclones. In this work, we have developed a data assimilativenorthwest Pacific regional ocean model to better initialize theocean state for the typhoon forecast system. We also have coupledthe regional ocean model with the GFDL typhoon model which iswell known as one of the most powerful tropical cyclone models inthe world. The domain of the regional ocean model is from 115°Eto 150°E and from 15°N to 52°N with 1/12° horizontal resolution.The numbers of grids are 420x444 horizontally and 40 vertically.The 3-dimensional variational assimilation routine has been fullycoupled with the regional ocean model to assimilate temperatureprofiles, and satellite-borne microwave sea surface temperatureand sea surface height anomaly. The GFDL typhoon model iscomposed of three nested domains. The outmost domain coversnorthwest Pacific to include other two domains, which move alongwith the typhoon track. The innermost domain has the finesthorizontal resolution of 1/12° to resolve the fine structure oftyphoons. Ocean reanalysis field, produced in this study from1998 to 2007, well represents the general circulation pattern suchas Kuroshio and Ryukyu Current. We have examined the effect ofthe ocean initialization, which suggests that the oceaninitialization may affect the typhoon intensity rather than its trackeven though there is not much room for the improvement of thetrack forecast. We also will discuss oceanic response to thetyphoon using the typhoon-ocean coupled model of which oceanstate is initialized by the ocean reanalysis.