Vertical Structure and Ice Production Processes of Shallow Convective Post-frontal Clouds Over the Southern Ocean in Marcus, Part I

Download or read book Vertical Structure and Ice Production Processes of Shallow Convective Post-frontal Clouds Over the Southern Ocean in Marcus, Part I written by Yazhe Hu and published by . This book was released on 2021 with total page 53 pages. Available in PDF, EPUB and Kindle. Book excerpt: A study of the vertical structure of post-frontal mesoscale cellular convection in the marine boundary layer over the Southern Ocean is presented. The central question of this two-part study regards cloud phase (liquid/ice) and associated precipitation growth mechanisms. In this first part, data from the Measurements of Aerosols, Radiation, and Clouds over the Southern Ocean (MARCUS) field campaign are analyzed, starting with a 75-hour case with continuous sea-surface-based thermal instability, modest surface heat fluxes, an open-cellular mesoscale organization, and very few ice nucleating particles (INPs). The clouds are lightly-precipitating and shallow (tops mostly ~ 2 km MSL), with weak up- anddowndrafts, and with cloud top temperatures generally around –10C to –18C. A cloud phase algorithm is presented that uses radiometer liquid water path, radar-derived ice water path, and lidar depolarization ratio. This algorithm classifies the vast majority (80% - 85%) of cloud profiles as liquid or liquid-dominated. This finding applies to all periods of postfrontal shallow mesoscale cellular convection in MARCUS, specifically 12 cases amounting to a total of 277 hours. The best predictors of ice presence are cloud top temperature, cloud depth, and INP concentration. Measures of convective activity and turbulence are found to be poor indicators of ice presence in the studied environment.