11th Conference on Atmospheric Radiation and the 11th Conference on Cloud Physics

Monday, 3 June 2002
Ice crystal formation in wave clouds, airborne studies -10 to -35C
David C. Rogers, NCAR, Boulder, CO; and P. J. DeMott
Poster PDF (210.6 kB)
Studies of ice formation in altocumulus standing lenticular wave clouds were conducted in Colorado and Wyoming during March 2000 using the University of Wyoming King Air and aerosol instrumentation from Colorado State University. Ten flights were made, and measurements were obtained for microphysical, thermodynamic, and kinematic properties. Cloud temperatures ranged from -10 to -37C. Aerosol properties (IN, CN and CCN) were measured upwind, within, and downwind of the clouds.

The relatively well defined vertical motions and simple air trajectories in these wave clouds were used for estimating parcel trajectories. This served as a basis for microphysical parcel modeling to examine the formation of ice crystals and cloud droplets. A summary of ice concentrations for thirty-five cloud penetrations during one flight is shown in the attached figure. There is a general trend of concentrations increasing at colder temperatures, although the scatter is a factor ~10x.

This paper presents observations from selected case studies and a summary based on all flights. Modeling results are also presented for selected cases, using inputs based on the observations. The emphasis of this research is testing the potential to improve predictions of ice particle concentrations that can be obtained by using measurements of ice nuclei and CCN. figure

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