Salinity Model

The real-time distribution of surface salinity in Chesapeake Bay is generated by running a real-time, three-dimensional hydrodynamic model.  This hydrodynamic model, called C3PO (Chesapeake 3-D Physical Oceanographic Model), solves a set of mathematical equations using the existing conditions such as observed freshwater inflows, winds and water levels to predict currents, salinity and temperature distributions in the Chesapeake Bay.

C3PO was designed by the NOAA Coast Survey Development Laboratory (CSDL) as the next generation water level and tide forecasting tool to replace Chesapeake Bay Operational Forecast System.  It is an implementation of Quoddy (http://www-nml.dartmouth.edu/circmods/gom.html), a finite element model. It is fully 3D, using an unstructured triangular horizontal grid and sigma vertical coordinate system (9700 nodes, 17925 elements, 15 layers) with a horizontal spatial resolution ranging from 100 meters to 10 kilometers. Baroclinic circulation is modeled with full salinity and temperature fields. The operational model uses real time data for surface wind forcing and to prescribe the non-tidal water level height at the mouth of the bay. River inputs from the USGS gauges control the estuarine circulation. Oceanic boundary conditions for salinity and temperature are monthly climatology. A Mellor Yamada 2.5 turbulence closure scheme is used, but will be replaced by a k-omega or k-epsilon closure in the near future.

The model is presently implemented in a "semi-operational" mode and is under evaluation.  A public distribution of the model is available from the Chesapeake Community Model Program (http://ccmp.chesapeake.org).