17 Jan 2022
17 Jan 2022
Status: a revised version of this preprint is currently under review for the journal AMT.

Cloud properties over the Southern Ocean during the MARCUS field campaign

Baike Xi1, Xiquan Dong1, Xiaojian Zheng1, and Peng Wu2 Baike Xi et al.
  • 1Department of Hydrology and Atmospheric Sciences, University of Arizona, Tucson, AZ, USA
  • 2Pacific Northwest National Laboratory, Richland, WA, USA

Abstract. To investigate the cloud properties over the Southern Ocean (SO), the MARCUS field campaign (41 to 69º S; 60 to 160º E) was conducted from October 2017 to March 2018, using ship-based measurements. To examine cloud properties over the mid-latitude and Polar regions, the study domain is separated into northern (NSO) and southern (SSO) parts of the SO with a demarcation line of 60° S. The total cloud fractions (CFs) were 77.9 %, 67.6 %, and 90.3 % for the entire domain, NSO and SSO, respectively, indicating that higher CFs were observed in the Polar region. Low-level clouds, deep cumulus, and shallow cumulus clouds are the three most common cloud types over the SO. For single-layered low-level clouds, mixed-phase clouds dominate with an occurrence frequency (Freq) of 54.5 %, while the Freq of the liquid and ice clouds were 10.1 % (most drizzling) and 17.4 % (least drizzling). The meridional distributions of low-level cloud boundaries are nearly independent of latitude, whereas the cloud temperatures increased ~ 8 K and atmospheric precipitable water vapor increased from ~5 mm at 69º S to ~18 mm at 43º S. The mean cloud liquid water paths over NSO were much larger than those over SSO. Most liquid clouds occurred over NSO with very few over SSO, whereas more mixed-phase clouds occurred over SSO than over NSO. There were no significant differences for ice cloud Freq between NSO and SSO. These results will be valuable for advancing our understanding of the meridional and vertical distributions of clouds and can be used to improve model simulations over the SO.

Baike Xi et al.

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Short summary
This study develops an innovative method to determine the cloud phases over the Southern Ocean (SO) using the combination of radar and lidar measurements during the ship-based field campaign of MARCUS. Results from our study show that the low-level, deep, and shallow cumuli are dominant, and the mixed-phase clouds occur more than single phases over the SO. The mixed-phase cloud properties are similar to liquid-phase (ice-phase) clouds in the midlatitudes (polar) region of SO.