Satellite Observations of SST-Induced Wind Speed Perturbations at the Submesoscale

Sea Surface Temperature (SST) modifies the turbulent mixing, drag, and pressure gradients within the marine atmospheric boundary layer. Local changes in surface winds arise from imbalances between the pressure gradient and turbulent stress divergence forces, which generate advective accelerations of near-surface flow from cool to warm SST, and decelerations from warm to cool SST. This phenomenon is well documented on scales of 100 - 1,000 km (the oceanic mesoscale). The nature of this air-sea coupling at scales on the order of 1 - 10 km (the submesoscale), however, remains relatively unknown.

The ASTER instrument onboard the Terra satellite acquires 90 m resolution infrared images which can be used to estimate SST. Dramatic temperature gradients along the Gulf Stream landward edge are observed in these high-resolution SST observations. These submesoscale features are not resolved by microwave SST measurements routinely used in the study of mesoscale air-sea interaction. The ASTER instrument also acquires 15 m resolution visible and near infrared observations of sun glitter which can be related to surface roughness. At low to moderate wind speeds, surface roughness and wind speed are highly correlated. Following the comparison of ASTER-derived wind speed estimates with concurrent TerraSAR-X wind speed estimates and anemometer measurements on nearby ocean observing moorings, we examined the surface wind response to submesoscale fronts in SST. Our analysis indicates that SST-induced wind speed perturbations can be observed at the scales of order 1 - 10 km, significantly smaller than previously suggested.