Coastal Upwelling Investigation in the Gulf of Thailand Using Ekman Transport and Sea Surface Temperature Upwelling Indices
Keywords:MUR-SST, ECMWF, upwelling index, monsoon wind, spatiotemporal
Two different upwelling indices: (1) Ekman transport upwelling index (UIET) and (2) sea surface temperature upwelling index (UISST) were evaluated determine likely locations of coastal upwelling occurring in the Gulf of Thailand (GoT). GoT covers the area between longitude 98.0°E to 106.0°E and latitude 5.0°N to 14.0°N. In addition, inter-annual and annual variability of UIET along the east and west coasts were also investigated. UIET was estimated using monthly averaged wind velocity during 2003--2018, while UISST was calculated based on the difference between coastal and oceanic monthly mean sea surface temperature at the same latitude. Based on spatial UIET, favorable upwelling conditions existed mainly along the east and west coasts during northeast and southwest monsoons, respectively. Furthermore, the favorable upwelling conditions were also found sparsely along the east coast and the west coast during the first and second inter-monsoon. The spatial UISST showed favorable upwelling condition along the west and east coasts around Ca Mau Cape during northeast and southwest monsoons. Meanwhile, during first and second inter-monsoons the favorable upwelling conditions rarely occurred. Disagreement of spatiotemporal coastal upwelling between UIET and UISST were likely due to the shallowness and bottom friction in the GoT. Considering inter-annual variability of meridionally averaged UIET along east and west coasts, it was found that favorable/unfavorable upwelling conditions were associated with Multivariate ENSO Index signal. Interestingly, annual cycle of meridionally averaged UIET along west and east coasts showed alternation of favorable and unfavorable upwelling conditions, respectively.
Authors who publish with Engineering Journal agree to transfer all copyright rights in and to the above work to the Engineering Journal (EJ)'s Editorial Board so that EJ's Editorial Board shall have the right to publish the work for nonprofit use in any media or form. In return, authors retain: (1) all proprietary rights other than copyright; (2) re-use of all or part of the above paper in their other work; (3) right to reproduce or authorize others to reproduce the above paper for authors' personal use or for company use if the source and EJ's copyright notice is indicated, and if the reproduction is not made for the purpose of sale.