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Unusual PSCs observed by LIDAR in Antarctica
Author(s) -
Stefanutti Leopoldo,
Morandi Marco,
Del Guasta Massimo,
Godin Sophie,
David Cristine
Publication year - 1995
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/95gl02085
Subject(s) - depolarization , supercooling , depolarization ratio , ternary operation , nitric acid , nat , lidar , polar , sulfate , chemistry , mineralogy , atmospheric sciences , materials science , geology , meteorology , physics , optics , inorganic chemistry , biophysics , organic chemistry , quantum mechanics , astronomy , computer science , biology , programming language
Polar Stratospheric Cloud (PSC) measurements by ground‐based LIDAR were carried out at Dumont d'Urville, Antarctica, during the years 1989 to 1993. From such measurements it can be seen that there are cases of PSCs that are not consistent with the simplest nitric acid trihydrate (NAT) theories. Several cases of long‐lasting, non‐depolarizing PSCs were detected at temperatures below or close to the NAT freezing threshold, at about 195°K, suggesting the presence of durable supercooled droplets. PSC cases showing depolarizing (frozen) particles well above the NAT expected threshold are also shown. These results seems to be more consistent with recent laboratory and in situ findings, suggesting a close link between sulfate and PSC particles through the HNO 3 ‐H 2 O‐H 2 SO 4 ternary system. In this framework, non‐depolarizing clouds observed below and close to 195°K would arise from the uptake of HNO 3 and water by the background particles before the freezing of the ternary system and the successive growth in nitric‐acid hydrates. Depolarizing “warm” PSCs are also consistent with the laboratory‐observed high melting point of the frozen sulfate core, that remains after NAT evaporation. A problematic PSC case, that cannot be easily explained by this theory is also shown.