Exploring relations between cloud morphology, cloud phase, and cloud radiative properties in Southern Ocean's stratocumulus clouds

  • Marine stratocumuli are the most dominant cloud type by area coverage in the Southern Ocean (SO). They can be divided into different self-organized cellular morphological regimes known as open and closed mesoscale-cellular convective (MCC) clouds. Open and closed cells are the two most frequent types of organizational regimes in the SO. Using the liDAR-raDAR (DARDAR) version 2 retrievals, we quantify 59 % of all MCC clouds in this region as mixed-phase clouds (MPCs) during a 4-year time period from 2007 to 2010. The net radiative effect of SO MCC clouds is governed by changes in cloud albedo. Both cloud morphology and phase have previously been shown to impact cloud albedo individually, but their interactions and their combined impact on cloud albedo remain unclear. Here, we investigate the relationships between cloud phase, organizational patterns, and their differences regarding their cloud radiative properties in the SO. The mixed-phase fraction, which is defined as the number of MPCs divided by the sum of MPC and supercooled liquid cloud (SLC) pixels, of all MCC clouds at a given cloud-top temperature (CTT) varies considerably between austral summer and winter. We further find that seasonal changes in cloud phase at a given CTT across all latitudes are largely independent of cloud morphology and are thus seemingly constrained by other external factors. Overall, our results show a stronger dependence of cloud phase on cloud-top height (CTH) than CTT for clouds below 2.5 km in altitude. Preconditioning through ice-phase processes in MPCs has been observed to accelerate individual closed-to-open cell transitions in extratropical stratocumuli. The hypothesis of preconditioning has been further substantiated in large-eddy simulations of open and closed MPCs. In this study, we do not find preconditioning to primarily impact climatological cloud morphology statistics in the SO. Meanwhile, in-cloud albedo analysis reveals stronger changes in open and closed cell albedo in SLCs than in MPCs. In particular, few optically thick (cloud optical thickness >10) open cell stratocumuli are characterized as ice-free SLCs. These differences in in-cloud albedo are found to alter the cloud radiative effect in the SO by 21 to 39 W m−2 depending on season and cloud phase.

Download full text files

Export metadata

Metadaten
Author:Jessica DankerORCiDGND, Odran SourdevalORCiDGND, Isabel L. McCoyORCiD, Robert WoodORCiD, Anna PossnerORCiDGND
URN:urn:nbn:de:hebis:30:3-752351
DOI:https://doi.org/10.5194/acp-22-10247-2022
ISSN:1680-7375
Parent Title (English):Atmospheric chemistry and physics
Publisher:EGU
Place of publication:Katlenburg-Lindau
Document Type:Article
Language:English
Date of Publication (online):2022/08/10
Date of first Publication:2022/08/10
Publishing Institution:Universitätsbibliothek Johann Christian Senckenberg
Release Date:2024/08/19
Volume:22
Issue:15
Page Number:19
First Page:10247
Last Page:10265
Note:
Data availability
The DARDAR-MASK v2.23 products are available on the AERIS/ICARE Data Center (https://www.icare.univ-lille.fr/, last access: 2 December 2020, Ceccaldi et al., 2013). MODIS cloud retrievals (MYD06_L2.6) are also obtained from AERIS/ICARE Data Center (Platnick et al., 2015).
Note:
Funding: Federal Ministry of Education and Research (BMBF) “Make our Planet Great Again – German Research Initiative” ; 57429624
Note:
Funding: NOAA Climate and Global Change Postdoctoral Fellowship Program ; NA18NWS4620043B
Note:
Gefördert durch den Open-Access-Publikationsfonds der Goethe-Universität
Institutes:Geowissenschaften / Geographie
Dewey Decimal Classification:5 Naturwissenschaften und Mathematik / 55 Geowissenschaften, Geologie / 550 Geowissenschaften
Sammlungen:Universitätspublikationen
Open-Access-Publikationsfonds:Geowissenschaften / Geographie
Licence (German):License LogoCreative Commons - CC BY - Namensnennung 4.0 International