Mixed Phase Clouds and Precipitation in Southern Ocean Cyclones and Cloud Systems Observed Poleward of 64°S by Ship Based Cloud Radar and Lidar

• Published in: Journal of Geophysical Research: Atmospheres
• Main Authors: Alexander, S. P., Mcfarquhar, G. M., Marchand, R., Protat, A., Vignon, É., Mace, G. G., Klekociuk, A. R.
• Other Authors: Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2021
• Subjects: lidar; mixed phase clouds; precipitation; radar; Southern Ocean; [SDU]Sciences of the Universe [physics]; East Antarctica; Antarc*; Antarctica
• Online Access: https://hal-insu.archives-ouvertes.fr/insu-03726949; https://hal-insu.archives-ouvertes.fr/insu-03726949/document; https://hal-insu.archives-ouvertes.fr/insu-03726949/file/JGR%20Atmospheres%20-%202021%20-%20Alexander%20-%20Mixed%25E2%2580%2590Phase%20Clouds%20and%20Precipitation%20in%20Southern%20Ocean%20Cyclones%20and%20Cloud%20Systems.pdf; https://doi.org/10.1029/2020JD033626

International audience Mixed phase clouds (MPCs), composed of both liquid and ice, are prevalent in Southern Ocean cyclones. A characterization of these clouds on fine vertical scales is required in order to understand the microphysical processes within these clouds, and for model and satellite evaluations over this region. We investigated three examples of cloud systems collected by ship mounted remote sensing instruments adjacent to East Antarctica at latitudes between 64°S and 69°S. These cases allow us to examine the properties of midlevel MPCs, with cloud tops between 2 and 6 km. Midlevel MPCs contain multiple layers of supercooled liquid water (SLW) embedded within ice during the passage of cyclones. SLW layers are capped by strong temperature inversions and are observed at temperatures as low as −31°C. Convective generating cells (GCs) are present inside supercooled liquid topped midlevel MPCs. The horizontal extent, vertical extent, and maximum upward Doppler velocity of these GCs were 0.6-3.6 km, 0.7-1.0 km, and 0.5-1.0 m s −1 , respectively, and are consistent with observations from previous lower latitude studies. Ice precipitation is nearly ubiquitous, except in the thinnest clouds at the trailing end of the observed systems. Seeding of lower SLW layers from above leads to periods with either larger ice particles or greater ice precipitation rates. Periods of supercooled drizzle lasting up to 2 h were observed toward the end of two of the three cyclone systems. This supercooled drizzle turns into predominantly ice precipitation as the result of seeding by ice clouds located above the precipitating SLW layer.