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.
Highlights
The Southern Ocean (SO) is one of the cloudiest and stormiest regions on the Earth (Chubb et al, 2013)
The total cloud fractions (CFs) were 77.9 %, 67.6 %, and 90.3 % for the entire domain, NSO and SSO, respectively, indicating that 22.7 % more clouds occurred in the Polar region than in the midlatitude region
When we plot the probability density functions (PDFs) of cloud liquid water path (LWP) for different types of clouds, we find that the PDFs of LWPs for high clouds (HGH) and high over mid (HOM) peak at less than 10 g m-2
Summary
The Southern Ocean (SO) is one of the cloudiest and stormiest regions on the Earth (Chubb et al, 2013). To investigate the aerosol and cloud properties over the SO, a field campaign called the Measurements of Aerosols, Radiation, and Clouds over the Southern Ocean (MARCUS) was conducted using the ship-based measurements between Hobart, Australia, and the Antarctic during the period October 2017-March 2018. Another field campaign, called South Ocean Clouds, Radiation, Aerosol Transport Experimental Study (SOCRATES) field campaign was conducted during austral summer from January 15 to February 26, 2018, which insitu measurements may use as a reference for this analysis. MARCUS ship-based instruments include AMF2 cloud radar, lidar, microwave radiometer, micropulse lidar, radiosonde sounding, precision solar pyranometer and precision infrared radiometer, as well as aerosol sensors Through these comprehensive observations over the SO, we are tentatively answering the following three scientific questions:.
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