Characterising observed mid-topped cloud regimes associated with Southern Ocean shortwave radiation biases

• Published in: Journal of Climate
• Main Authors: Mason, Shannon, Jakob, Christian, Protat, Alain, Delanoë, Julien
• Other Authors: Monash Weather and Climate (MWAC), Monash University Clayton, Centre for Australian Weather and Climate Research (CAWCR), SPACE - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2014
• Subjects: Southern Ocean; Cloud radiative effects; Climate classification/regimes; Lidars/Lidar observations; Radars/Radar observations; Model evaluation/performance; [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology; [SDE.MCG]Environmental Sciences/Global Changes
• Online Access: https://hal.science/hal-01005147; https://hal.science/hal-01005147/document; https://hal.science/hal-01005147/file/jcli-d-14-00139_1.pdf; https://doi.org/10.1175/JCLI-D-14-00139.1

International audience Clouds strongly affect the absorption and reflection of shortwave and longwave radiation in the atmosphere. A key bias in climate models is related to excess absorbed shortwave radiation in the high-latitude Southern Ocean. Model evaluation studies attribute these biases in part to mid-topped clouds, and observations confirm significant mid-topped clouds in the zone of interest. However, it is not yet clear what cloud properties can be attributed to the deficit in modelled cloud. Present approaches using observed cloud regimes do not sufficiently differentiate between potentially distinct types of mid-topped clouds and their meteorological contexts. This study presents a refined set of mid-topped cloud sub-regimes for the high-latitude Southern Ocean, which are distinct in their dynamical and thermodynamic background states. Active satellite observations from CloudSat and CALIPSO are used to study the macrophysical structure and microphysical properties of the new cloud regimes. The sub-grid scale variability of cloud structure and microphysics is quantified within the cloud regimes by identifying representative physical cloud profiles at high resolution from the DARDAR cloud classification mask. The mid-topped cloud sub-regimes distinguish between stratiform clouds under a high inversion and moderate subsidence; an optically-thin cold-air advection cloud regime occurring under weak subsidence and including altostratus over low cloud; optically thick cloud with frequent deep structures under weak ascent and warm mid-level anomalies; and a mid-level convective cloud regime associated with strong ascent and warm advection. The new mid-topped cloud regimes for the high-latitude Southern Ocean will provide a refined tool for model evaluation and the attribution of shortwave radiation biases to distinct cloud processes and properties.