November 2, 2018 - 2:00 pm
November 2, 2018 - 3:00 pm
Address120 David L. Boren Blvd, Room 5600, Norman, OK 73072 View map
Phase partitioning of Southern Ocean boundary layer clouds: comparisons of airborne in situ measurements and CAM5 simulations
Low level clouds over the Southern Ocean, with annual fractions of 80 to 90%, are an essential control of the energy budget. Climate models fail to capture the observed radiative fluxes over the Southern Ocean, in part because they generally produce lower cloud fraction and less supercooled liquid water than detected by satellite. However, these retrievals are highly uncertain and poorly evaluated due to a lack of in situ measurements in the region.
Two aircraft campaigns recently took place over the Southern Ocean: the O2/N2 Ratio and CO2 Airborne Southern Ocean Study (ORCAS) based out of Punta Arenas, Chile, and the Southern Ocean Clouds, Radiation, Aerosol Transport Experimental Study (SOCRATES) based out of Hobart, Tasmania. This presentation will describe comparisons of the phase partitioning and relative humidity fields between the Community Atmosphere Model version 5 (CAM5) and in situ measurements from ORCAS. Simulations are found to underestimate the frequency of supercooled liquid at relatively colder temperatures (<-10°C) and overestimate relative humidity within ice phase conditions.
In addition, the microphysical properties of boundary layer clouds are compared between ORCAS and SOCRATES, which took place in different sectors of the Southern Ocean. A much greater frequency of supercooled liquid water is observed in SOCRATES compared with ORCAS, potentially due to the different terrestrial influences on the campaigns’ sampling regions.