Measurements of the Size, Shape, Scattering Phase Function and Extinction Coefficient of Ice Crystals at South Pole Station

Stratton Park Engineering Co., Inc., Boulder CO

Investigators

Abstract

9909593 Lawson This project is a three-year study of the radiative characteristics of cirrus clouds and the light-scattering properties of ice crystals in the atmosphere at South Pole Station, using a high-resolution digital cloud particle imager to automatically classify cloud particles by size and shape. A number of theoretical and experimental studies have demonstrated that particle size and shape strongly affect the radiative effects of cloud particles, and specifically ice crystals. Two cloud particle imagers will be operated in Antarctica in cooperation with an ongoing radiation transfer program, with field work to be carried out in the 2000-01 and 2001-02 austral summer seasons. Particle images, concentrations, and size distributions will be processed on site and preliminary analyses will be conducted to assure data quality. Current software capabilities of the system allow the rejection of artifacts, the computation of various size and shape parameters, of scattering characteristics, and of ice/water fraction. The individual observations, as well as the collective statistics will significantly add to several concurrent experiments concerning the emission characteristics of snow, of ice crystals in the atmosphere, and of greenhouse gases near the surface. This data, together with measurements of environmental conditions such as cloud base altitude, temperature, and humidity structure, will allow the development of a climatology of cloud and cloud particle properties, and of new algorithms to substantially improve representations of radiation processes in general circulation models. ***