| Summary: | This model is based onthe Regional Ocean Modeling System (ROMS), a primitive-equation, hydrostatic, and free-surface ocean model that solves the Reynolds-averaged form of the Navier–Stokes equations. ROMS is a fully nonlinear, finite-difference model that uses terrain-following (sigma) vertical coordinates and horizontal orthogonal or curvilinear Arakawa C grid (Shchepetkin and McWilliams, 2003, 2005; Haidvogel et al., 2008).The model domain (290 x 150) is rotated 52.14° clockwise to better resolve the NZNES and spans 332 km offshore at the widest point (near North Cape). The domain has horizontal resolution of approximately 2 km, which roughly captures coastline variability and still resolves the continental shelf and slope without large computational cost. The model has 30 vertical sigma layers and model bathymetry was interpolated from the 250 m resolution bathymetric data set built by the National Institute of Water and Atmospheric Research (NIWA - https://niwa.co.nz/our-science/oceans/bathymetry). We use a vertical discretisation scheme that increases the resolution near the surface and bottom by applying stretching function type 4 and transformation equation option 2 (Shchepetkin and McWilliams, 2005, 2009). The vertical resolution is higher at the upper 200 m (from 4 to 30 layers). On the slope (depth<1000 m), the vertical resolution is higher than 66 m and in the open ocean the thickest level is 233 m (3838.6 m depth). Baroclinic modes are resolved using a time step of 180 s, while the barotropic time step is 6 s. Model surface forcing is from the Japanese atmospheric 55-year reanalysis for driving ocean models (JRA55-do, Tsujino et al., 2018). A previous study demonstrated that JRA55-do had the highest correlation with observed winds in comparison to other atmospheric forcing datasets in the Southwest Pacific (Taboada et al., 2019). Atmospheric forcing fields of wind speed, net shortwave radiation, downward longwave radiation, relative humidity, temperature, rain, and pressure are specified every 3 h ...
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