Boundary layer roll statistics from SAR

The Atmospheric Boundary Layer (ABL) mean flow frequently consists of an organized secondary circulation in the form of counter rotating rolls embedded in it. Theory predicts this is the case for a range of thermodynamic conditions. Although generally associated with the formation of "cloud streets", numerical and theoretical studies suggest that rolls should be present whenever there is sufficient shear to organize the convection, including cloud free conditions. Through their association with clouds and their modification of the mean low level flow, ABL rolls alter air-sea interaction processes, surface energy fluxes, and the earth radiational balance. Despite their potential importance to climate there exist no prior studies that can establish the extent and statistical frequency of roll occurrence. Synthetic Aperture Radar (SAR) can detect ABL roll signature on the ocean surface. A first regional climate scale attempt to construct ABL roll frequency statistics from the RADARSAT SAR observations is described.