The Regional Ocean Modeling System (Shchepetkin & McWilliams, 2005), which has three-dimensional and time-dependent primitive equations with a free surface, was used in this model simulation. The parameterization of vertical mixing process of the submodel is based on Mellor and Yamada (1982), which solves the 2.5-layered turbulent kinetic energy equations.
The model domain, extended northeastward and covered the PRE and the shelves off Guangdong in the NSCS. The study area was discretized into an Arakawa C-grid system with 1-km horizontal resolution. The bottom topography was retrieved from the navigation maps provided by the Hong Kong Maritime Department and the China Maritime Safety Administration. The model had 30 vertical levels with terrain-following s coordinates (Song & Haidvogel, 1994) and adopted higher resolutions (<0.2 m) in both the surface and bottom boundary layers to better resolve the dynamics inside these boundary layers. A detailed description of model implementation and validation are described in Zu and Gan (2015).
The model was nested within an NSCS model with a coarser resolution (~3 km; Gan et al., 2015). This NSCS model was further downscaled from a hindcast simulation in the China Seas Multiscale Modeling System (Gan et al., 2016). This downscaling system ensured that the remote effect from the NSCS circulation during the cruise period can be well resolved.
The model was initialized with temperature and salinity on 15 June 2011 from the NSCS simulation, and the remote forcing of velocities and hydrographic variables from the NSCS model along the three open boundaries (OBs) were imposed (Figure 1a) by using the OB conditions of Gan and Allen (2005). Tidal forcing along the OBs was derived from the harmonic constants based on the Oregon State University Tidal Inversion Software (Egbert & Erofeeva, 2002), which has been validated by Zu et al. (2008), which was implemented along the OBs by an active Flather (1976)-type OB condition. We included eight tidal constituents, M2, K1, S2, O1, N2, P1, K2, and Q1 and used Hong Kong Observatory meteorological variables observed at the weather station on Waglan Island to calculate bulk heat flux.