Numerical study of monsoon effect on Green island wake

The wind effect on Kuroshio-induced island wake downstream of Green Island, Taiwan, is studied using a depth-averaged shallow-water model. The seasonal monsoon effect on spatial-temporal scales, such as the aspect ratio, dimensionless width, and Strouhal number, as well as the relative propagation speed of Green Island vortices, is studied. It is found that a NE monsoon has a more pronounced effect on wake characteristics than a SW monsoon does in terms of net speed and vorticity, aspect ratio, and dimensionless width. Vortices are pushed back and packed close to the north of the island with a smaller area of recirculation when Kuroshio flows against the NE monsoon; vortices are pushed farther downstream with a larger area of recirculation when Kuroshio flows in favor of the SW monsoon. However, the wind effect on temporal variation of island wake seems less significant. The period of vortex shedding is between 14.2 and 15.3 hours. The corresponding Strouhal number is between 0.116 and 0.125, and the relative propagation speed of vortices is nondimensional, between 0.51 and 0.56. These values are in good agreement with the results of previous reports.