Air-Sea Fluxes and Atmospheric Boundary Layer Variability Across Ocean Fronts

Atmospheric and oceanic variability occurring across scales ranging from millimeters to tens of kilometers presents a difficult observational and modeling challenge. Regions of particular interest are strong SST frontal gradient regions such as the Gulf Stream. These regions typically lead to some of the highest seasonal surface heat fluxes across the global ocean, and are also typically where some of the largest uncertainties in models and satellite flux products exist. This is due in part to the strong dependency of the interaction between the ocean and the atmosphere on varying spatial and temporal scales. Recent studies indicate that resolving these frontal air-sea interaction processes requires spatial resolution of at least 25 kilometers. Direct surface flux measurements across strong SST gradient regions are scarce; nearly all studies of the air-sea fluxes and response to the SST gradients are predicated on satellite data (with relatively lower resolution and possibly a combination of non-contemporaneous inputs) or model simulations, with their inherent uncertainty.

In this talk, we will show results of multiple observations of direct covariance flux measurements from multiple ship transects across the Gulf Stream. These observations were taken during the CLIvar Mode Water Dynamic Experiment (CLIMODE) near 38^oN and the Processes Driving Exchange at Cape Hatteras (PEACH) experiment. In addition, bulk fluxes using ship-measured winds, temperature, and humidity are also calculated for comparison with the direct measured fluxes; the direct measured fluxes reveal structures and response times to atmospheric flow that provide more information on the coupling than the bulk fluxes are capable of providing. These fluxes are placed within the context of the evolving marine atmospheric boundary layers, as measured from rawinsondes launched from the ships.