PARAMETERIZATION OF THE PARTICLE SIZE SPECTRUM OF ICE CLOUDS IN TERMS OF THE AMBIENT TEMPERATURE AND THE ICE WATER CONTENT.

A data set obtained in cirrus clouds has been examined to deduce any dependencies of the particle size spectral form or the crystal habit on the temperature. It was found that both form of the spectra and crystal habit changed systematically with temperature, the largest change occurring between minus 40 and minus 50 degree C. These findings are consistent with previously found dependencies between lidar backscatter measurements and temperature. A preliminary scheme for parameterizing the cirrus particle size spectra for crystal dimensions greater than 20 mu m in terms of the temperature and the ice water content is described. The visible extinction in cirrus is estimated.