AN ERS-1 SYNTHETIC-APERTURE-RADAR IMAGE OF ATMOSPHERIC LEE WAVES

An ERS 1 synthetic aperture radar (SAR) image of the island Hopen show s a distinct 7.6-km wavelength wave phenomenon near the island. This w ave phenomenon is interpreted as the surface imprint on open water of atmospheric lee waves. The pattern is visible in the SAR image, since the lee waves modulate the horizontal wind speed near the ocean surfac e which, in turn, modulates the surface roughness and the radar cross section. The physical setting for the observation is presented and dis cussed. The lower bound on horizontal wind speed modulation is estimat ed to range from 3 +/- 2 ms(-1) (for the wind speed minima) to 12 +/- 2 ms(-1) (for the wind speed maxima) based upon the observed radar cro ss-section modulation and the ERS 1 scatterometer wind retrieval model CMOD4. The wavelength and wind speed modulation are consistent with l inear lee wave model predications. The model uses an atmosphere with a n exponential profile of the Scorer parameter (ratio of buoyancy frequ ency to wind speed) to represent a shallow, ground-based inversion lay er observed at Bear Island and a bell-shaped barrier to represent the forcing effects of Hopen.