The Structures of Summer Convective Clouds in Eastern Montana. I: Natural Clouds

Abstract

The microstructures and precipitation-producing mechanisms in 93 clouds in the vicinity of Miles City, Montana have been explored through airborne measurements. Small cumulus and cumulus complexes contained high cloud particle concentrations and had narrow particle size spectra; broader spectra and lower particle concentrations were measured in embedded cumulus. Ice particle concentrations in the small and embedded cumulus were generally <1 ??1, although they occasionally reached 10's ??1; these clouds precipitated only occasionally. Ice enhancement processes appeared to work particularly effectively in the cumulus complexes where the average concentrations of ice particles often reached 100's ??1; these clouds generally precipitated. Ice mass concentrations ranged from values of ?0.001 g m?3 in the small developing cumulus to ?6 g m?3 in some of the cumulus complexes. The size spectra of the precipitable particles generally followed an exponential distribution; their growth was dominated by ice-phase processes.