DIAGNOSIS OF SUPERCOOLED LARGE DROP CONDITIONS USING CLOUD WATER CONTENT AND DROP CONCENTRATION

Two of the most challenging aspects of in-flight icing are accurately diagnosing and forecasting the presence of supercooled large droplets (SLD) and high values of supercooled liquid water content (SLWC). Such conditions have been the focus of several recent field programs, including the NASA Glenn Research Center's SLD Research Project, the Alliance Icing Research Study, and the Winter Icing and Storms Program. Through daily forecasting, real-time flight direction, on-board experience, case studies and associated climatological research, patterns associated with the spectrum of SLWC and droplet size are beginning to emerge. The interplay of ideal synoptic- and meso-scale forcing, clouds with ideal temperatures and moisture content, and specific thermodynamic structures appears to be important to the amount of water and the droplet size ranges produced. In this paper, observations from environments with a variety of combinations of supercooled liquid water content and droplet size will be presented. These environments include continental capped convection, "clean" layers isolated from the boundary layer, pockets found between precipitation areas, and diurnally-varying, long-lived stratus clouds.