Observations of mesoscale variability in marine surface-layer momentum flux events

In this paper we present case studies from two ONR-funded field campaigns which had, among many goals, the study of the properties of the marine atmospheric surface layer. These were the ONR MBL/ARI and the ONR Shoaling Waves Initiative. There are two sources of data to be discussed here. The first is the NOAA-based light aircraft known as the LongEZ, which flew missions down to about 20 m above the surface of the water while collecting a suite of high temporal resolution measurements of wind, heat, etc. The second data set consists of Synthetic Aperture Radar (SAR) imagery of the ocean surface that can, at times, image spatial patterns of the instantaneous wind-forcing of that surface. The SAR imagery shows what have become known to be the footprints of atmospheric roll vortices: parallel line segments of textured streaks of enhanced backscatter whose spacing scales with the boundary-layer depth. The in situ turbulence measurements confirms the presence of atmospheric roll vortices. Those turbulence measurements also show mesoscale structure in the distribution of individual momentum-flux events associated with the atmospheric roll vortices.