Doppler Radar Observations of Mammatus

Abstract

Observations of mammatus-like cloud features associated with a convective rain shower were obtained using a vertically pointing 8-mm-wavelength Doppler radar. The radar's excellent sensitivity and resolution allowed even very weak, finescale features of the cloud to be resolved. The mammatus were located 3?5 km above ground along the underneath side of an anvil-like stratiform region of the storm cloud and preceded the arrival of precipitation. Both reflectivity and velocity exhibited strongly periodic patterns, with larger downward motions and larger reflectivities occurring together. The mammatus lobes were separated by about 90 s or approximately 1 km, horizontally. The mammatus features could be traced more than 500 m upward into the cloud echo interior where the amplitude of the vertical velocity oscillations was greatest. The measured vertical velocities of particle motions ranged from +0.5 to ?3.0 m s?1. The observed reflectivity and velocity patterns suggest that although evaporation was acting to shape the mamma as they descended toward the echo bottom, other mechanisms may have been responsible for their initial formation in the interior region of the cloud echo.