Microstructure of Radar Echo Layers in the Clear Atmosphere

Abstract

Previous observations of clear air echo layers by high-resolution radar are reviewed briefly and compared with theoretical models. Quantitative radar reflectivity records reveal a variety of features common to these echo layers. In particular, some of the records show that the backscatter from layers only a few meters thick is strongly anisotropic with maximum reflectivity at 0° incidence angle, although the? 0° echoes are not specular in the strict sense. The anisotropy is consistent with the presence of large shears across the thin layers. The data leave open the question of whether or not microscale (> 1 m) instability always or necessarily precedes the occurrence of large-amplitude (10?100 m) breaking waves.