High-Resolution Airborne Radar Observations of Mammatus

Abstract

High-resolution Doppler radar observations of mammatus clouds coupled with soundings of the preanvil and anvil environments provide a unique opportunity to examine previously reported observations of, and evaluate various hypotheses of, mammatus formation. These observations confirm the general hypothesis for mammatus formation advanced by Ludlam and Scorer, and provide detail of the cloud interior structure. Specifically, the radar observations indicate that mammatus elements are reminiscent of eddy circulations with a weak downdraft core flanked by horizontal convergence and divergence at the top and base of the cloud, respectively. Doppler spectral width measurements, however, yielded values of only 2?3 m s?1, indicating only weak turbulent motions within individual mammatus elements. Reflectivity analyses of mammatus elements indicate a firm link to the parent anvil. A dual-Doppler analysis of the parent anvil indicates that the larger-scale environment where the mammatus exist is characterized by the existence of gravity waves or shear overturning. It is hypothesized that these circulations might play a role in the initiation of this particular outbreak of mammatus.