모의 태풍 합성 재분석 바람장을 이용한 북서태평양 극치풍속 추정

Abstract

In this study, extreme wind speeds in the western North Pacific (WNP) were estimated using reanalysis wind fields synthesized with empirical typhoon vortex model. First, to select reanalysis wind field suitable for the extreme value analysis in the WNP, the accuracy of various reanalysis wind fields as evaluated using the Korea Meteorological Administration (KMA) buoy data and the Joint Typhoon Warning Center (JTWC) best track data from 2010 to 2018. The suitability was determined based on the maximum wind speed and the center position of the typhoon period, the simulated performance of offshore winds nearshore the Korean Peninsula, and the period of available data. The results showed that the Fifth-generation European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis (ERA5) data was the most suitable data for the extreme value analysis in this study. The empirical typhoon vortex model was synthesized with the ERA5 wind fields to improve the tendency to underestimate the maximum wind speed during the typhoon period in the selected ERA5 data. The empirical typhoon vortex model used has the advantage of being able to realistically reproduce the asymmetric winds of typhoon using the gale/storm-forced wind radii information in the 4 quadrants of typhoon. Using a total of 39 years of the synthesized reanalysis wind fields from 1980 to 2018 in the WNP, extreme value analysis is performed using the General Pareto Distribution (GPD) model based on the Peak-Over-Threshold (POT) method, which can be used effectively in case of insufficient data. The results showed that the extreme analysis using the synthesized wind data significantly improved the problem to underestimate the extreme wind speeds compared to using only reanalysis wind data. Considering the difficulty of obtaining long-term observational wind data over ocean, the results of extreme value analysis based on the synthesized wind fields developed in this study can be used as basic data for the design of offshore structures.