A characterization of clouds and precipitation over the Southern Ocean
from synoptic to micro scales during the CAPRICORN field campaigns
Abstract
The persistent Southern Ocean (SO) shortwave radiation biases in climate
models and reanalyses have been associated with the poor representation
of clouds, precipitation, aerosols, the atmospheric boundary layer, and
their intrinsic interactions. Capitalizing on shipborne observations
collected during the Clouds Aerosols Precipitation Radiation and
atmospheric Composition Over the Southern Ocean (CAPRICORN) 2016 and
2018 field campaigns, this research investigates and characterizes cloud
and precipitation processes from synoptic to micro scales. Distinct
cloud and precipitation regimes are found to correspond to the seven
thermodynamic clusters established using a K-means clustering technique,
while less distinctions are evident using the cyclone and (cold) front
compositing methods. Cloud radar and disdrometer data reveal that light
precipitation is common over the SO with higher intensities associated
with cyclonic and warm frontal regions. While multiple microphysical
processes and properties are present in several cloud regimes, ice
aggregation appears to be dominant in deep precipitating clouds. Mixed
phase, and in some cases, riming was detected in shallow convective
clouds away from the frontal conditions. Two unique clusters with
contrasting cloud and precipitation properties are observed over the
high-latitude SO and coastal Antarctica, suggesting distinct physical
processes therein. Through a single case study, in-situ and
remote-sensing data collected by an overflight of the Southern Ocean
Clouds Radiation Aerosol Transport Experimental Study (SOCRATES) were
also evaluated and complement the ship-based analysis.