Future typhoon and storm surges under different global warming scenarios: case study of typhoon Haiyan (2013)

The present work evaluates potential future typhoon and storm surges around the islands of Samar and Leyte in the Philippines taking into account monthly mean sea surface temperatures, atmospheric air temperature, and relative humidity (hereafter, SST, AAT, and RH) from MIROC5 according to four scenarios proposed by IPCC AR5. Super-typhoon Haiyan (2013), which caused catastrophic damage to coastal areas in the Philippines due to its high winds and storm surge, was used as the case study storm given that it was one of the tropical cyclones recorded in modern history. In this study, the Advanced Research Weather Research and Forecasting Model (ARW-WRF) is used to estimate the characteristics of both the present-day Haiyan and a typhoon with a similar return period under the climate condition of the year 2100. The unstructured, Finite Volume Community Ocean Model (FVCOM) was used to estimate both the present and potential future storm surges. The research has two main focuses. First, both the historical event and its storm surge are simulated and contrasted with field measurements of the storm surge height in order to prove the accuracy of the model. Second, the future typhoon and storm surge are estimated using the monthly mean value differences in SST, AAT, and RH from MIROC5 between 2011-2020 and 2091-2100 for the different scenarios. The characteristics of the simulated typhoon route and storm surge heights agree well with those of the best track data and field measurements. The numerical results of the future typhoon show that, if climate change is considered to only increase SST, its intensity and storm surge will be larger than under the present climate. The minimum sea-level pressure (hereafter, MSLP) of the future typhoon under scenario RCP 8.5 would be about 21 hPa lower and the storm surge 2.7 m higher than in the present climate. However, if SST, AAT, and RH are also taken into account, then the increase in typhoon intensity will not be as marked as if only SST is considered, with the MSLP under RCP 8.5 decreasing only by 13 hPa and the storm surge increasing by 0.7 m. The results of the present research thus suggest that while increases in SST can contribute to the intensification of future typhoons, increases in AAT and RH will somehow moderate this effect. Nevertheless, all scenarios considered point out to stronger typhoons and higher storm surges, clearly highlighting the perils posed by future climate change.