Continuation of Ice Crystal Observations at South Pole Station and Collection of Cloud Microphysical Data on Ross Island in Support of ANTCI and RIME

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This project is the continuation of a previous study that supported the collection of the size, shape, concentration and scattering phase function of over 1 million individual ice crystals at South Pole Station during February 2001 and 2002. This first statistically large data set of high-definition digital images of antarctic ice crystals showed that these consisted of bullet rosettes, budding rosettes, solid columns, and diamond dust. Rosettes accounted for only about 25% of the number of ice particles, but comprised about 70% of the particle mass, while diamond dust accounted for about 30% of the number of particles, but only about 15% of the mass. As part of this project, the continued ground-based collection of microphysical data at South Pole station will be enhanced by long-duration (greater than 24 hour) vertical profiles of cloud microphysical and radiation data with a new tethered balloon system that lifts a cloud particle imager and other meteorological instrumentation to an altitude of two kilometers. The tethered balloon data will provide the first insights into the microphysics of clouds at South Pole and Ross Island, since there have been virtually no previous in situ cloud microphysical measurements at either location. A number of theoretical and experimental studies at lower latitudes have demonstrated that particle size and shape strongly affect the radiative effects of cloud particles, and specifically ice crystals. 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.