Characterisation of low-base and mid-base clouds and their thermodynamic phase over the Southern Ocean and Arctic marine regions

• Published in: Atmospheric Chemistry and Physics
• Main Authors: Dietel, Barbara, Sourdeval, Odran, Hoose, Corinna
• Other Authors: Institute of Meteorology and Climate Research, Karlsruhe Institute of Technology = Karlsruher Institut für Technologie (KIT), Laboratoire d’Optique Atmosphérique - UMR 8518 (LOA), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Lille-Centre National de la Recherche Scientifique (CNRS), Institute for Meteorology and Climate Research (IMK), ANR-20-CE92-0008,CDNC4aci,Concentration en nombre des gouttelettes – restitutions satellitaires améliorées par modélisation atmosphérique pour l'analyse des interactions aérosols-nuages(2020)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2024
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDU.STU.ME]Sciences of the Universe [physics]/Earth Sciences/Meteorology; Sea ice; Southern Ocean
• Online Access: https://hal.science/hal-04682638; https://hal.science/hal-04682638/document; https://hal.science/hal-04682638/file/Dietel-2024aa.pdf; https://doi.org/10.5194/acp-24-7359-2024

International audience The thermodynamic phase of clouds in low and middle levels over the Southern Ocean and the Arctic marine regions is poorly known, leading to uncertainties in the radiation budget in weather and climate models. To improve the knowledge of the cloud phase, we analyse 2 years of the raDAR-liDAR (DARDAR) dataset based on active satellite instruments. We classify clouds according to their base and top height and focus on low-, mid-, and mid-to low-level clouds as they are the most frequent in the mixed-phase temperature regime. Low-level single-layer clouds occur in 8 %-15 % of all profiles, but single-layer clouds spanning the mid-level also amount to approx. 15 %. Liquid clouds show mainly a smaller vertical extent but a horizontally larger extent compared to ice clouds. The results show the highest liquid fractions for low-level and mid-level clouds. Two local minima in the liquid fraction are observed around cloud top temperatures of -15 and -5 °C. Mid-level and mid-to low-level clouds over the Southern Ocean and low-level clouds in both polar regions show higher liquid fractions if they occur over sea ice compared to the open ocean. Low-level clouds and mid-to low-level clouds with high sea salt concentrations, used as a proxy for sea spray, show reduced liquid fractions. In midlevel clouds, dust shows the largest correlations with liquid fraction, with a lower liquid fraction for a higher dust aerosol concentration. Low-level clouds clearly show the largest contribution to the shortwave cloud radiative effect in both polar regions, followed by mid-to low-level clouds