Coastal oceanography applications of spaceborne synthetic aperture radar (SAR) in the Middle Atlantic Bight (MAB)

This study provides basic interpretative tools necessary to understand spaceborne synthetic aperture radar (SAR) observations of ocean surface signatures in the Middle Atlantic Bight (MAB). The research focuses on SAR imaged features related to dynamical processes over the continental shelf and near-shelf region. Particular attention is given to signatures acquired during summer upwelling. Other processes and features addressed include the detection of coastal plumes and fronts, oceanic internal waves, bathymetric features, as well as ocean surface atmospheric signatures prevalent in SAR imagery.; The ability of SAR to detect upwelling conditions and track their evolution in the MAB is demonstrated. The connection between localized low backscatter and seasonal upwelling in the coastal zone is established for the first time using spaceborne SAR together with supporting in situ and satellite thermal and ocean color data. Reduced backscatter over areas of active upwelling is attributed to a combination of factors including water viscosity, atmospheric stability, and the presence of biogenic slicks. Low backscatter patterns imaged by SAR are found to match upwelling patterns in satellite sea surface temperature (SST) observations. The abundance of slick filaments within upwelling areas is frequently indicated by SAR and supports satellite ocean color observations of enhanced biological activity resulting from upwelling-enhanced nutrient availability.; Backscatter sensitivity to SST under slick-free conditions is investigated. A coefficient of thermal stability is defined using a simplified thermal front model. The coefficient parameterizes the change in backscatter as a function of boundary layer stability and wind speed. Its dependence on wind speed and on the atmospheric diabatic state is found to be similar to that of the drag coefficient. Values for the coefficient of thermal stability are also in general agreement with previous results based on tower radar observations.; The ability of SAR sea surface roughness observations to capture outflow patterns from multiple estuarine sources along the MAB coast is documented. In particular, the spaceborne imaging of a Delaware Bay twin-front plume is shown and its recurrent nature confirmed. Spaceborne SAR imaging of estuarine outflow patterns is found to be consistent with available airborne data and historical in situ salinity observations.