A Doppler Radar Observation on Wave-like Echoes Generated in a Strong Vertical Shear

[摘要] Wave-like echoes were observed in a weak rain cloud by a Doppler radar on September 6, 1989. The wave-like echoes presented as a series of band echoes with a wavelength of 3.5km. The wave-like echoes were generated in a strong vertical shear at a height between 3 and 4km and oriented perpendicular to the shear vector between 3 and 4km. The minimum Richardson number at the shear layer is 0.14. These features are consistent with the condition of Kelvin-Helmholtz (K-H) instability. The vertical cross section of the wave-like echoes were expressed as a series of reflectivity cores and undulation of an isopleth of Doppler velocity. The undulation of Doppler velocity, which is induced by K-H instability, is assumed to cause the horizontal accumulation of precipitation particles and adiabatic heating to form the reflectivity core at the melting level.

[学科分类] 大气科学