Effects of Model Coupling on Typhoon Kalmaegi (2014) Simulation in the South China Sea

Kenny T.C Lim Kam Sian,Han Zhang,Hailong Liu,Changming Dong,Renhao Wu

doi:10.3390/atmos11040432

Abstract

Typhoon Kalmaegi (2014) in the South China Sea (SCS) is simulated using a fully coupled atmosphere–ocean–wave model (COAWST). A set of sensitivity experiments are conducted to investigate the effects of different model coupling combinations on the typhoon simulation. Model results are validated by employing in-situ data at four locations in the SCS, and best-track and satellite data. Correlation and root-mean-square difference are used to assess the simulation quality. A skill score system is defined from these two statistical criteria to evaluate the performance of model experiments relative to a baseline. Atmosphere–ocean feedback is crucial for accurate simulations. Our baseline experiment successfully reconstructs the atmospheric and oceanic conditions during Typhoon Kalmaegi. Typhoon-induced sea surface cooling that weakens the system due to less heat and moisture availability is captured best in a Regional Ocean Modeling System (ROMS)-coupled run. The Simulated Wave Nearshore (SWAN)-coupled run has demonstrated the ability to estimate sea surface roughness better. Intense winds lead to a larger surface roughness where more heat and momentum are exchanged, while the rougher surface causes more friction, slowing down surface winds. From our experiments, we show that these intricate interactions require a fully coupled Weather Research and Forecasting (WRF)–ROMS–SWAN model to best reproduce the environment during a typhoon.

Highlights

Typhoons ( called tropical cyclones (TC) or hurricanes, depending on location; hereafter TC for simplicity) are one of Earth’s most destructive natural disasters, which induce rapid and severe modulations in both the atmospheric and marine environments through heat and momentum energy transfers across the air–sea interface
The track geometric distance difference from the JMA track and TC translation speed given in Figure 3 quantify the results presented above
From 12:00 12 September, the translation speeds steadily increase until 12:00 on 14 September, when Typhoon Kalmaegi passed over the Philippines

Summary

Introduction

Typhoons ( called tropical cyclones (TC) or hurricanes, depending on location; hereafter TC for simplicity) are one of Earth’s most destructive natural disasters, which induce rapid and severe modulations in both the atmospheric and marine environments through heat and momentum energy transfers across the air–sea interface. TCs cause huge loss of lives and billions of dollars worth of damage every year. Atmosphere 2020, 11, 432 vulnerability to TC-induced storm surges, flooding, landslides, and structural damage. The changing global climate further complicates TC forecasting [2]. Intensive TC research is imperative to help minimize threats to human lives and property and to aid in the more profound understanding of atmospheric and oceanic changes occurring during a TC event and mitigating its impacts. TC-induced violent wind forces significant ocean responses and induces extreme changes in ocean water properties (e.g., water temperature and salinity) that adversely affect marine organisms. Due to the high socio-economic impact of TCs, their analysis and prediction are of primary concern in the scientific community

Objectives

Methods

Results

Conclusion