Antarctic clouds, supercooled liquid water and mixed phase, investigated with DARDAR: geographical and seasonal variations

• Published in: Atmospheric Chemistry and Physics
• Main Authors: Listowski, Constantino, Delanoë, Julien, Kirchgaessner, Amélie, Lachlan-Cope, Tom, King, John, C.
• Other Authors: SPACE - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), British Antarctic Survey (BAS), Natural Environment Research Council (NERC)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2019
• Subjects: [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph]; [SDU.STU.ME]Sciences of the Universe [physics]/Earth Sciences/Meteorology; Antarc*; Antarctic; Antarctica; East Antarctica; Sea ice; South pole; West Antarctica
• Online Access: https://insu.hal.science/insu-02136183; https://insu.hal.science/insu-02136183/document; https://insu.hal.science/insu-02136183/file/acp-19-6771-2019.pdf; https://doi.org/10.5194/acp-19-6771-2019

International audience Antarctic tropospheric clouds are investigated using the DARDAR (raDAR/liDAR)-MASK products between 60 and 82 • S. The cloud fraction (occurrence frequency) is divided into the supercooled liquid-water-containing cloud (SLC) fraction and its complementary part called the all-ice cloud fraction. A further distinction is made between SLC involving ice (mixed-phase clouds, MPC) or not (USLC, for unglaciated SLC). The low-level (< 3 km above surface level) SLC fraction is larger over seas (20 %-60 %), where it varies according to sea ice fraction, than over continental regions (0 %-35 %). The total SLC fraction is much larger over West Antarctica (10 %-40 %) than it is over the Antarctic Plateau (0 %-10 %). In East Antarctica the total SLC fraction-in summer for instance-decreases sharply pole-wards with increasing surface height (decreasing temperatures) from 40 % at the coast to < 5% at 82 • S on the plateau. The geographical distribution of the continental total all-ice fraction is shaped by the interaction of the main low-pressure systems surrounding the continent and the orography, with little association with the sea ice fraction. Opportunistic comparisons with published ground-based supercooled liquid-water observations at the South Pole in 2009 are made with our SLC fractions at 82 • S in terms of seasonal variability, showing good agreement. We demonstrate that the largest impact of sea ice on the low-level SLC fraction (and mostly through the MPC) occurs in autumn and winter (22 % and 18 % absolute decrease in the fraction between open water and sea ice-covered regions, respectively), while it is almost null in summer and intermediate in spring (11 %). Monthly variability of the MPC fraction over seas shows a maximum at the end of summer and a minimum in winter. Conversely, the USLC fraction has a maximum at the beginning of summer. However, monthly evolutions of MPC and USLC fractions do not differ on the continent. This suggests a seasonal-ity in the glaciation process in ...