Mixed‐Phase Clouds and Precipitation in Southern Ocean Cyclones and Cloud Systems Observed Poleward of 64°S by Ship‐Based Cloud Radar and Lidar

Abstract

These clouds remain difficult to model correctly due to the interplay of microphysical and dynamical processes which regulate their formation, maintenance, and decay (Sotiropoulou et al., 2016), and because the scales over which these processes occur are substantially smaller than the resolution of climate and weather prediction models. The observed longevity of MPCs indicates that the removal of ice crystals from the cloud through gravitational sedimentation must be balanced by a continuous source of liquid water. Intracloud processes including updrafts and turbulent mixing, or a continuous supply of new liquid at cloud base, must be sufficient to replenish the liquid water (Korolev & Field, 2008;Rauber & Tokay, 1991). The correct modeling of cloud phase partitioning between ice and liquid water is necessary to match observations of reflected shortwave radiation (

Challenging and Improving the Simulation of Mid‐Level Mixed‐Phase Clouds Over the High‐Latitude Southern Ocean

“…The synoptic circulation and the cloud properties during our case study are thoroughly analyzed in Alexander et al. (2021). We provide here a brief description of the evolution of clouds and precipitation from observations to help the interpretation of model results.…”

“…During the 15 and 16 February, the warm front moves to the south‐east of the station and dissipates. The ship thus enters the warm sector, the mid‐tropospheric flow above it progressively changes from a northerly to a westerly direction while the low‐level flow, characterized by a clear katabatic jet at about 500 m a.s.l., keeps an easterly direction (Alexander et al., 2021). Meanwhile, the cold front of the system remains far from the coast over the Southern Ocean and the extra‐tropical cyclone progressively weakens at the west of Mawson and disappears during the second half of the 16 February.…”

“…Further details on radar and lidar data processing, uncertainties and analysis are available in Alexander et al. (2021). Radiosondes were launched from the ship every 6 h—0530, 1130, 1730, 2330 UTC (Sato et al., 2018)—and standard meteorological variables were also measured, including downward shortwave and longwave radiative fluxes.…”

“…This case study corresponds to the third precipitation event described in Alexander et al. (2021). We pay particular attention to the challenging representation of SLW layers at the top of mid‐altitude clouds preceding and following the front.…”

“…During the austral summer 2017–2018, the Measurement of Aerosols, Radiation and Clouds over the Southern Ocean (MARCUS) campaign was conducted aboard the Australian ice‐breaker Aurora Australis as the ship made three return crossings of the Southern Ocean from Hobart to East Antarctica in order to resupply the three Australian Antarctic stations (Alexander et al., 2021; Sato et al., 2018).…”