Properties of Cirrus Generating Cells

Abstract

Particle size spectra were measured during 20 hr of sampling in cirrus generating cells (uncinus, stratus, spissatus, thunderstorm anvil) and the particle concentration, mean crystal length, ice water content, reflectivity factor, and precipitation rate were calculated from these spectra. Average values of the physical properties in the generating cells were: Ice crystal concentration: 10,000?25,000m?3 Mean crystal length: 0.6?1.0 mm Particle habit: bullet, rosette, column (75%)-plate (25%) Ice crystal density. 0.6?0.9 gm m?3 Ice water content. 0.15?0.25 gm ?3 Reflectivity factor: 5.0?20.0 mm6?3 Precipitation rate. 0.5?0.7 mm hr?1 Growth was found to be downward, reaching a maximum ice water content just below the base of the generating cell. The maximum ice water contents (not including the thunderstorm anvil) were found in cirrus uncinus. Liquid water was not found throughout the cirrus sampling by measurement with the Johnson-Williams hot wire liquid water meter; however, we believe that liquid water is present as a transient phase.