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Abstract

A one-way nesting technique is utilized when constructing an Oceanic Regional Circulation Model (ORCM) from an Oceanic Global Circulation Model (OGCM) with a low resolution. As the information of the OGCM is downscaled, the boundary and initial conditions of the ORCM can only have large-scale information. Small-scale fluctuations can occur naturally when running the ORCM, but they cannot develop sufficiently in a short time to cause errors. To reduce errors, Pham and Hwang (2020) proposed a method of generating small-scale fluctuations along kinetic energy spectrum of the ocean and adding them to boundary conditions of the ORCM. The present study extended this method to apply it to each vertical layer of the coastal area.The regional energy spectrum of the research area is analyzed using the Discrete Cosine Transform to construct small-scale information arbitrarily. The larger scales of the spectrum obtained from the OGCM are extended to the smaller scales, and then this spectrum is transformed to velocity fields using the Inverse Discrete Cosine Transform. As new velocity fields with small-scale motions are added to original one with large-scale motions, the boundary conditions of the ORCM can have high-resolution information. When this method is applied to the ORCM in coastal areas, it is expected to increase the accuracy as applied to the ORCM in ocean areas.