A033-0011
Phase Characterization of Cold Sector Southern Ocean Cloud Tops

Tuesday, 8 December 2020
Poster
Troy Zaremba, University of Illinois at Urbana Champaign, Atmospheric Sciences, Urbana, IL, United States, Robert Rauber, Univ Illinois Urbana-Champaign, Urbana, IL, United States, Greg M McFarquhar, Cooperative Institute for Mesoscale Meteorological Studies, University of Oklahoma, Norman, OK, United States, Joseph Finlon, University of Washington, Atmospheric Sciences, Seattle, WA, United States and Daniel Miles Stechman, Cooperative Institute for Mesoscale Meteorological Studies, Norman, OK, United States
Abstract:
For a given cloud, whether the cloud top is predominately made up of ice crystals or supercooled liquid droplets plays a large role in the clouds overall radiative effects. This study uses collocated airborne radar, lidar, and thermodynamic data from twelve high-altitude flight legs during the Southern Ocean Clouds, Radiation, Aerosol Transport Experimental Study (SOCRATES) to characterize Southern Ocean (SO) cold sector cloud top (top 96 m) phase as a function of cloud top temperature (CTT). A training dataset was developed to create probabilistic phase classifications based on High Spectral Resolution Lidar data and HIAPER Cloud Radar data. These classifications were then used to identify dominant cloud top phase. Case studies are presented illustrating examples of supercooled liquid water at cloud top at different CTT ranges present over the SO (-3ºC < CTTs < -28ºC). Of all clouds sampled, 75.6% of cloud tops had CTTs less than 0ºC. Considering only clouds with subfreezing CTTs, the dominant phase at cloud top in 89.9% of clouds was liquid, 0.4% was ice, and 9.7% was uncertain. Liquid-bearing cloud tops were found at CTTs as cold as -30ºC.
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