Measured correlation between roll-vortex signatures and radar-inferred sea surface roughness

The authors present aircraft measurements of near-surface atmospheric boundary layer roll signatures and radar-derived sea surface roughness. These data are coincident in space and time. This unique feature supports attempts to quantitatively link SAR backscatter signatures to boundary layer roll impacts. The open-ocean data were collected at an altitude of 12-20 m from NOAA´s Long-EZ aircraft using its turbulence probe and down-looking Ka-band radar scatterometer. They find marked correlation between measured fluctuations in the along-wind component of the horizontal wind velocity and radar backscatter for the spatial scale of 1 to 1.5 km. Close agreement between normalized modulation amplitudes suggests the surface slope variance is changing linearly with wind speed. These data were collected within thirty minutes of a RADARSAT SAR overpass where apparent boundary layer impacts of the same orientation, spatial dimensions, and amplitude are prevalent in the SAR backscatter image.