Comparison of observed and model‐computed low frequency circulation and hydrography on the New England Shelf

The finite volume coastal ocean model (FVCOM) is configured to study the interannual variability of circulation in the Gulf of Maine (GoM) and Georges Bank. The FVCOM‐GoM system incorporates realistic time‐dependent surface forcing derived from a high‐resolution mesoscale meteorological model (MM5) and assimilation of observed quantities including sea surface temperature and salinity and temperature fields on the open boundary. An evaluation of FVCOM‐GoM model skill on the New England shelf is made by comparison of computed fields and data collected during the Coastal Mixing and Optics (CMO) Program (August 1996–June 1997). Model mean currents for the full CMO period compare well in both magnitude and direction in fall and winter but overpredict the westward flow in spring. The direction and ellipticity of the subtidal variability correspond but computed magnitudes are around 20% below observed, partially due to underprediction of the variability by MM5. Response of subtidal currents to wind‐forcing shows the model captures the directional dependence, as well as seasonal variability of the lag. Hydrographic results show that FVCOM‐GoM resolves the spatial and temporal evolution of the temperature and salinity fields. The model‐computed surface salinity field compares well, except in May when there is no indication of the fresh surface layer from the Connecticut River discharge noted in the observations. Analysis of model‐computed results indicates that the plume was unable to extend to the mooring location due to the presence of a westward mean model‐computed flow during that time that was stronger than observed. Overall FVCOM‐GoM captures well the dynamics of the mean and subtidal flow on the New England shelf.