Radar observations of wave perturbations in a low level windsurge

10 cm radar observations, in a visually clear atmosphere, of parallel echo bands along the wind with superimposed transverse structure are presented and compared with radiosonde-radarwind data. The mode of echo generation is discussed in terms of incoherent back scatter from a turbulent layer and in terms of specular reflection from a continuous inversion layer. The former process is shown to be the more realistic of the two. The mechanism of amplified shear-gravity waves is capable of accounting for the transverse structure only. The hypothesis that the observed primary bands are set up by unstable perturbations in boundary layer flow over a concave surface (so-called Görtler vortices) is not inconsistent with the theoretical prediction which takes into account topography and excitation, the latter being supplied by an observed strong wind surge.