Improving cross-scale hydrodynamic simulations in the Chesapeake Bay with physically based calibration
Estuaries, as transitional zones between land and ocean, exhibit highly nonlinear, cross-scale hydrodynamic processes that present substantial challenges for numerical modeling. Using Chesapeake Bay as an example, we demonstrate a physically based calibration procedure with observation-derived parametrizations, together with a high-resolution unstructured model without bathymetry smoothing. The results indicate that highly turbid water greatly affects the downward penetration of solar radiation, particularly in the upper Bay and tributaries. By incorporating the spatially varying Jerlov water types derived from satellite-based Kd490 data, we systematically improve water temperature simulations across the Bay, reducing the average RMSE to 0.484 °C (0.775 °C) for surface (bottom) temperature at 121 long-term monitoring stations maintained by EPA's Chesapeake Bay Program. Moreover, the presence of mud layers is found to facilitate tidal propagation in tributaries, thereby enhancing saltwater intrusion there. By applying spatially varying bottom drag coefficients calculated from the observed sediment types, we achieve significant improvements in salinity simulations, with an average RMSE of 0.809 PSU (1.331 PSU) for surface (bottom) salinity. In general, the present study reduces temperature and salinity errors by ∼60% compared to previous modeling studies in the Bay. This study underscores the advantages of physically based calibration procedures that help make the model results more defensible.
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