Stratocumulus Precipitation Properties over the Southern Ocean Observed
from Aircraft during the SOCRATES campaign
Abstract
Precipitation plays an important role in various processes over the
Southern Ocean (SO), ranging from the hydrological cycle to cloud and
aerosol processes. The main objective of this study is to characterize
SO precipitation properties. We use data from the Southern Ocean Clouds
Radiation Aerosol Transport Experimental Study (SOCRATES), and leverage
observations from airborne radar, lidar, and in situ probes. For the
cold-topped clouds (cloud-top-temperature < 0°C), the phase of
precipitation with reflectivity > 0 dBZ is predominately
ice, while reflectivity < -10 dBZ is predominately liquid.
Liquid-phase precipitation properties are retrieved where radar and
lidar are zenith-pointing. The power-law relationships between
reflectivity (Z) and rain rate (R) are developed, and the derived Z-R
relationships show vertical dependence and sensitivity to the
intermediate drops (diameters between 10-40 μm). Using derived Z-R
relationships, reflectivity-velocity (ZV) retrieval method, and a
radar-lidar retrieval method, we derive rain rate and other
precipitation properties. The retrieved rain rate from all three methods
shows good agreement with in-situ aircraft estimates. Rain rate features
the prevalence of light precipitation (<0.1 mm hr-1). We
examine the vertical distribution of precipitation properties, and found
that rain rate, precipitation number concentration, precipitation liquid
water all decreases as one gets closer to the surface, while
precipitation size and width increases. We also examine how cloud base
rain rate (RCB) depends on cloud depth (H) and aerosol concentration
(Na) for particles with diameter greater than 70nm, and we find a linear
relationship between RCB and H3.6Na-1.