Thesis (M.Eng.) - Asian Institute of Technology, 2011

The tidal inlet at Songkhla, located in southeast coast of Thailand is highly populated coast and used for economical development such as international port and fishery harbor. The high wave at the beach of Songkhla is generated by the northeastern winds, the stormy season. The coastal erosion in the area force due to both these wave induced current and fluctuation of sea level. Ocean waves and storm surges of future climate are also expected to change characteristics from the present climate and are the dynamic side issue of climate variation and change. It is necessary to seriously consider the impacts of these dynamic phenomena for coastal disaster prevention and reduction, However, there is no clear indication about projected future wave climate data in the Gulf of Thailand and due to the lack of research studies carried out related to the offshore wave climate. This study focused on analyzing the future wave condition at Songkhla using a numerical wave model with input of future projected wind data from selected Global Circulation Models (GCMs) scenario. Surface wind forcing was obtained from 2 GCMs (GFDL CM 2.1 and ECHAM 5), with A2 scenario that had been downscaled by CSIRO{u201F}s Cubic Conformal atmospheric Model (CCAM) at 0.5lat, 0.5lon resolution over Gulf of Thailand. Twenty years time slice from CCAMs and NCEP-DOE reanalysis II, 1981-2000 was representing current period and 2041-2060 and 2081-2100 periods were taken as future periods. A third generation wave model, Mike 21 SW was employed to derive the wave climate for present and future periods. Results found that CCAMs wind is trend to slightly change in future periods over the Gulf of Thailand. At the end of the 21st century, the mean wind speed projected to increase in northeast monsoon period and it will be decreased slightly in southeast monsoon over the Songkhla. Moreover, the mean wind direction is projected to have decreases both in northeast monsoon and southwest monsoon periods. With all forcing scenarios, mean significant wave height is projected to increase and the mean wave direction trend to change anti-clock wise direction from present climate at Songkhla in the 21st century. However, the magnitude of the projected change was relatively small.