A054-08
Simulating multi-layer mixed-phase clouds over the Southern Ocean using convection-permitting WRF model
Tuesday, 8 December 2020: 19:28
Virtual
Son Cong Hoang Truong1, Yi Huang2, Francisco Lang3, Steven Thomas Siems1 and Michael Manton1, (1)Monash University, School of Earth, Atmosphere and Environment, Melbourne, VIC, Australia, (2)The University of Melbourne, School of Earth Sciences, Melbourne, VIC, Australia, (3)Monash University, School of Earth, Atmosphere and Environment, Melbourne, Australia
Abstract:
Clouds over the Southern Ocean (SO) play a critical role in modulating the regional radiation budget. However, processes that are shaping the low- and mid-top clouds over the SO remain poorly understood, which directly contribute to the persistent large radiative biases in this region in climate models and reanalysis products. A recent study (Truong et al. 2020) documented a
climatology of the marine atmospheric boundary layer and lower free troposphere over the SO constructed from 2186 atmospheric soundings taken from four recent field campaigns [CAPRICORN 2016&2018, SOCRATES (Jan-Feb 2018), MARCUS (Oct 2017-Apr 2018) and Macquarie Island (2016-2018)]. They highlighted that a multi-layer cloud structure is frequently present in the vicinity of fronts and subantarctic mesoscale cyclones. These regions are spatially correlated with the largest biases in the shortwave radiation budget, which underscores the complexity of radiative transfer through multiple cloud layers and the ensuing heating/cooling rates.
In this study, a case study, which includes convection-permitting simulations made with the WRF model, is presented to examine the occurrence and evolution of multi-layer mixed-phase clouds. The simulations are evaluated against radiosonde, cloud radar, lidar observations collected from the CAPRICORN 2018, along with a high-resolution Himawari-8 satellite data set. The sensitivity of the simulations to the model resolution, microphysical scheme and planetary boundary layer scheme is also explored. The observations and simulations are employed to examine the formation, maintenance, and dissipation of the multi-layer mixed-phase clouds over the high-latitudes of the SO. In particular, the role of cold/warm air advection as well as the detrainment of convection associated with mesocyclones, as proposed in Truong et al. (2020), will be examined. Implication of the findings to the climate community will be discussed.
Keywords: marine atmospheric boundary layer, multi-layer clouds, radiation bias, Southern Ocean
