The clouds over Southern Ocean during MARCUS field experiments

Abstract:

The Southern Ocean (SO) is one of the cloudiest and stormiest regions and the most pristine place on the Earth. However, we have very little knowledge about how the cloud forms at such clean environment. To investigate the aerosol and cloud properties over SO, a field campaign called MARCUS was conducted using the ship-based measurements between Hobart, Australia and Antarctic during the period October 2017-March 2018. The ship-based instruments include ARM cloud radar, lidar, microwave radiometer, micropulse lidar, radiosonde sounding. Along the ship tracks, the study domain is separated into northern and southern parts with a demarcation line of 60^º. Preliminary results show that there are more clouds in southern part (CF=90.3%) than in northern part (CF=67.6%), where the single-layered low-level cloud is the most frequent type among all the clouds. Within the low clouds, the liquid, mixed, ice and other phases are 10.1%, 54.5%, 17.3%, and 18.1%, respectively. The thicker clouds are strongly related to the occurrence of precipitation, but the higher layer mean liquid water content is not necessary to result a higher occurrence frequency of precipitation. Over the northern part of the domain, the mixed-phase and the liquid phase clouds have similar vertical distributions of radar reflectivity, Doppler velocity and spectrum width. While over the southern part of the domain, those distributions for the mixed-phase clouds are similar to the ice phase clouds. The results from this study provide observational constraints on model development and validation of satellite retrievals.