ERS-1 SAR IMAGES OF ATMOSPHERIC GRAVITY-WAVES

ERS-1 synthetic aperture radar (SAR) images of atmospheric gravity wav es over the ocean are discussed, Several case studies are presented in detail, It is shown that the well-organized long wavelength (1 to 10 km) wave phenomena which often are seen in SAR images over the ocean m ay be atmospheric gravity waves, The waves appear in the SAR images be cause they modulate the surface wind speed which in turn modulates the surface roughness and the radar cross section, The wavelength may be measured directly from the SAR image, and the mean wind speed and wind speed modulation near the ocean surface may be estimated from the obs erved radar cross section modulation using a wind retrieval model, The atmospheric gravity waves usually were generated by the approach or p assing of a meteorological front. Atmospheric soundings and a two-laye r model for the lower troposphere indicate that, in general, the obser ved atmospheric wave phenomena could have been supported by accompanyi ng temperature inversion layers and wind shears.