Atmospheric modulation of microwave backscatter from the ocean surface


  • R. J. Zamora,

  • R. A. Kropfli


During a month-long experiment near San Clemente Island, California, the San Clemente Ocean Probing Experiment (SCOPE), unusual radar echoes were observed from an X-band Doppler radar operated by the National Oceanic and Atmospheric Administration Environmental Technology Laboratory from a cliff 573 m above mean sea level. These radar images were often obtained whenever a strong marine inversion was observed below the level of the radar. The unusual characteristics of the specific event analyzed here were the observed wavelength of the periodic pattern, about 2 km, and its lack of movement during the 15-min period during which specific features of the pattern, for example, the “wave” crest, could be identified. Several explanations were considered but rejected because of their conflict with the observations and known characteristics of ocean waves. The simplest explanation consistent with all of the observations was that of microwave propagation through a marine inversion which was supporting a low-amplitude standing wave in the lee of the island. The plausibility of this hypothesis was supported by a simple ray-trace calculation that simulated propagation through an analytical two-dimensional field of modified refractive index that represented the essential characteristics of the observed refractive index profile.