Airborne Measurements and Observations in Cirrus Clouds.

Abstract : Fourteen case studies of airborne measurements in cirrus clouds are described. For each case information is given on the location of the flight, the synoptic situation (with accompanying satellite IR and visible photographs), the types, sizes and mass concentrations of ice particles in the clouds, and the distribution of the ice mass concentration among particle sizes at different altitudes. From simultaneous measurements of ice mass concentrations and ice particle number concentrations, mean ice particle masses are derived: They range from about 0.3 to 30 micrograms. Low number concentrations of ice particles are generally associated with low ice mass concentrations and high number concentrations with high mass concentrations. The total ice mass concentrations in cirrus clouds generally increase with increasing temperature. Maximum values of the total ice mass concentration did not exceed the atmospheric water vapor content for water saturated conditions (about 0.1 and 1.0 g/cubic meter at -45 and -20C respectively) except when the cirrus originated from cumulonimbus tops.