Characteristics of Mixed-Phase Clouds Adjacent to the Antarctic Coast Observed by Ship-Based Radar and Lidar

Several recent field campaigns over the Southern Ocean and coastal East Antarctica included a suite of remote sensing instruments deployed aboard ships and at coastal sites. We use cloud radar and lidar data, supplemented by frequent radiosonde launches, to characterise mixed-phase clouds (MPCs) associated with the passage of cyclonic systems. We will focus here on presenting the properties of mid-level mixed-phase clouds (MPCs), at altitudes 2-4km, present in the cold sectors of cyclones adjacent to the Antarctic coast. We find that these mid-level MPCs contain multiple layers of super-cooled liquid water (SLW) embedded within (and precipitating) ice and are evident after the surface pressure has risen from its minimum. SLW layers are capped by a strong temperature inversion and are observed at temperatures as low as −31C. Convective cells are evident near the top of these complex MPCs, with downdrafts exceeding 2 m/s during one case: the horizontal extent of these cells is around 1.2 – 1.8 km. Ice precipitation is nearly ubiquitous, except in the thinnest clouds at the trailing end of the observed systems, with seeding of lower SLW layers from above leading to periods with either more ice or larger ice particles.