ROMS High Resolution Hindcasts for Delaware River and Bay

To support the development of the Delaware River and Bay Operational Nowcast/Forecast System (DBOFS), high resolution hindcasts have been made using the Regional Ocean Modeling System (ROMS) community model from the head of tide at Trenton, NJ out to the continental shelf break. The construction of the high resolution grid (HRG) using the DELFT3D RGFGRID software package is first discussed and contrasted with the previous medium resolution grid (MRG). Results for two 15-day hindcasts in 1984 (one 27 March – 10 April during high flow and the other 10–24 September 1984 during low How) on both grids are compared with the National Ocean Service (NOS) Delaware River and Bay 1984 Circulation Survey measurements of water surface elevation, currents, salinity, and temperature. Total water level RMS errors range from 15 cm at Cape May, NJ to 37 cm at Trenton, NJ on both grids under high flow. RMS errors on the MRG (11–22 cm) are less than on the HRG (16–37 cm) under low flow, due to differences in the specification of the ocean boundary subtidal water level. Estuarine station current speed and direction RMS errors are generally reduced on the HRG by 5 cm/s and 10 degrees, respectively. Salinity (0.8–3.5 PSU) and temperature (0.4–3.1 °C) RMS errors are at most stations comparable on both grids. Total water level results for the HRG are evaluated for an extended seven-month, March – September 1984, hindcast and are comparable to the two 15-day hindcast results. The tidal water level error component is determined to range from 15–24 cm. To seek further reduction, several HRG tide simulations using different open boundary conditions are performed. Plans for further testing and development are then presented.