The Southern Ocean Clouds, Radiation, Aerosol Transport Experimental Study (SOCRATES): An Observational Campaign for Determining Role of Clouds, Aerosols and Radiation in Climate System

The Southern Ocean (SO) region is one of the cloudiest on Earth, and as such, clouds determine the region's albedo and play a major role in climate. In addition, there is evidence that Earth's climate sensitivity and the location of the Intertropical Convergence Zone depend upon SO clouds. But, due to poor process-level understanding, climate models are challenged by uncertainties and biases in the simulation of clouds, aerosols, and air-sea exchanges in this region. Apart from satellites, there have been sparse observations of clouds, aerosols, precipitation, radiation and the air-sea interface in the SO region with which to assess and improve model accuracy. Plans for the upcoming international, multi-platform program, SOCRATES, will be presented. Based on feedback on observational and modeling requirements from a 2014 workshop conducted at the University of Washington, a plan will be described for obtaining a comprehensive dataset on the boundary-layer structure and associated vertical distributions of liquid and mixed-phase cloud and aerosol properties across a range of synoptic settings, especially in the cold sector of cyclonic storms. Four science themes are under development: improved climate model simulation of SO cloud and boundary layer structure in a rapidly varying synoptic setting; understanding seasonal and synoptic variability in SO cloud condensation and ice nucleus concentration and the role of local biogenic sources; understanding supercooled liquid and mixed-phase clouds and their impacts; and advancing retrievals of clouds, precipitation, aerosols, radiation and surface fluxes. Testable hypotheses for each theme will be identified. The observational strategy consists of long-term ground-based observations from Macquarie Island and the Davis Antarctic research station, continuous data collection onboard Antarctic supply ships, satellite retrievals, and a dedicated field campaign covering 2 distinct seasons using in-situ and remote sensors on low- and high-altitude aircraft, UAVs, and a ship-borne platform. A timeline for these activities will be proposed.