EXTREME WAVES GENERATED BY TYPHOON BOLAVEN(201215) IN SOUTHERN KOREAN WATERS

Abstract

Unusual extreme waves were generated by Typhoon Bolaven (201215) in the Southern Korean Waters (SKW) and gave destructive damages to the breakwaters of Seogwipo Harbor at Jeju Island. The waves were far exceeding the design wave height (Hs50yrs 9.3m) and their duration was 14hours. The duration is a very significant factor as much as the design wave height for breakwater armor stability in terms of cumulative damages. A significant increase in strong typhoon intensity and duration in North West Pacific (NWP) due to global warming has been reported and also in landfall typhoons on Korea/Japan in a recent decade. The frequency of typhoon passed SKW region had an inter-annual and also a decadal variation and decreased in recent years. but several strong typhoons were occurred. Bolaven was affected by high pressure distribution located above the warm eddy region to track toward NNW rather than NE as usual in August. The extreme waves were analyzed with respect to typhoon genesis, evolution of the waves through extensive measured data and model simulation. Numerical models of TC96 for the wind fields and WAM4.5.2 for the waves were used after calibration with measured data and correction of Cd in wave growth term. They produced reasonably good results. It was found that the extreme waves were evolved by combination of distant large swell and strong wind seas generated by consistent strong winds from front right quadrant0yrs 9.3m) and their duration was 14hours. The duration is a very significant factor as much as the design wave height for breakwater armor stability in terms of cumulative damages. A significant increase in strong typhoon intensity and duration in North West Pacific (NWP) due to global warming has been reported and also in landfall typhoons on Korea/Japan in a recent decade. The frequency of typhoon passed SKW region had an inter-annual and also a decadal variation and decreased in recent years. but several strong typhoons were occurred. Bolaven was affected by high pressure distribution located above the warm eddy region to track toward NNW rather than NE as usual in August. The extreme waves were analyzed with respect to typhoon genesis, evolution of the waves through extensive measured data and model simulation. Numerical models of TC96 for the wind fields and WAM4.5.2 for the waves were used after calibration with measured data and correction of Cd in wave growth term. They produced reasonably good results. It was found that the extreme waves were evolved by combination of distant large swell and strong wind seas generated by consistent strong winds from front right quadrant