Testing the diagnosis of marine atmospheric boundary-layer structure from synthetic aperture radar

A method for calculating Obukhov lengths and drag coefficients from high-re solution synthetic aperture radar (SAR)-generated wind speed imagery was te sted. The wind imagery was created from six Radarsat scenes collected off t he East Coast of the United States during cold air outbreaks in the winter of 1997. Comparisons were made between the drag coefficients and Obukhov le ngths obtained from the SAR method and those obtained from the Tropical Oce an-Global Atmosphere Coupled Ocean-Atmosphere Response Experiment 2.5 Bulk Flux Algorithm. This algorithm uses corresponding buoy data as input. In ge neral, the drag coefficients were in good agreement. Agreement was less pre cise between the two methods when comparing Obukhov lengths. It is importan t that the SAR imagery be inspected for the signature of convection (mottli ng) before implementation of the SAR method. Potential sources of disagreem ent between the results of the two methods are discussed.