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Abstract. Abnormal storm waves cause coastal disasters along the coasts of Korean Peninsula and Japan in the East/Japan Sea (EJS) in winter, arising due to developed low pressures during the East Asia winter monsoon. The generation of these abnormal storm waves during rough sea states were studied and hindcast using an atmosphere-wave coupled modelling system. Wind waves and swell due to developed low pressures were found to be the main components of abnormal storm waves. The meteorological conditions that generate these waves are classified into three patterns based on past literature that describes historical events as well as on numerical modelling. In hindcasting the abnormal storm waves, a bogussing scheme originally designed to simulate a tropical storm in a mesoscale meteorological model was introduced into the modelling system to enhance the resolution of developed low pressures. The modelling results with a bogussing scheme showed improvements in terms of resolved low pressure, surface wind field, and wave characteristics obtained with the wind field as an input.

Storm surge and storm wave simulations in Seto Inland Sea (SIS) in Japan were conducted for Typhoon Yancy (9313) and Chaba (0416) using an atmosphere (MM5)-wave (SWAN)-ocean (POM) modeling system. In the coupled modeling system, a new method for wave-current interaction in terms of momentum transfer due to whitecapping in deep water and depth-induced wave breaking in shallow water was considered. The calculated meteorological and wave fields show good agreement with the observations in SIS and its vicinities. The storm surge results also exhibit good accordance with the observations in SIS. To resolve a number of islands in SIS, we also performed numerical experiments with different grid resolutions and obtained improved results from higher resolutions in wave and ocean circulation fields.

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Climate indices such as El Niño-Southern Oscillation in the Pacific Ocean were investigated to find out a relationship between multi-decadal fluctuations of climate change and tropical storms, in particular typhoon in North West Pacific based on the historical record of typhoon-induced disasters. It was found that the ratio of the category.5 typhoon among the all historical typhoon and recorded developed-low pressure systems in the West Pacific was increased in La Niña dominant period. It is foreseeable that attentions on more intensified and frequent tropical storms, typhoon, should be drawn in the forthcoming La Niña dominant period from this study. The similar results were obtained from the historical record of hurricanes in the Atlantic and in the East Pacific Ocean.