TY - JOUR A1 - Peter, Thomas A1 - Luo, Beiping A1 - Wirth, Martin A1 - Kiemle, Christoph A1 - Flentje, Harald A1 - Yushkov, Vladimir A. A1 - Khattatov, Vyacheslav A1 - Rudakov, Vladimir V. A1 - Thomas, Andreas A1 - Borrmann, Stephan A1 - Toci, Guido A1 - Mazzinghi, Piero A1 - Beuermann, Jürgen A1 - Schiller, Cornelius A1 - Cairo, Francesco A1 - Di Donfrancesco, Guido A1 - Adriani, Alberto A1 - Volk, C.-Michael A1 - Strom, Johan A1 - Noone, Kevin A1 - Mitev, Valentin A1 - MacKenzie, Robert A. A1 - Carslaw, Kenneth S. A1 - Trautmann, Thomas A1 - Santacesaria, Vincenzo A1 - Stefanutti, Leopoldo T1 - Ultrathin Tropical Tropopause Clouds (UTTCs): I. Cloud morphology and occurrence T2 - Atmospheric chemistry and physics / Discussions N2 - Subvisible cirrus clouds (SVCs) may contribute to dehydration close to the tropical tropopause. The higher and colder SVCs and the larger their ice crystals, the more likely they represent the last efficient point of contact of the gas phase with the ice phase and, hence, the last dehydrating step, before the air enters the stratosphere. The first simultaneous in situ and remote sensing measurements of SVCs were taken during the APE-THESEO campaign in the western Indian ocean in February/March 1999. The observed clouds, termed Ultrathin Tropical Tropopause Clouds (UTTCs), belong to the geometrically and optically thinnest large-scale clouds in the Earth's atmosphere. Individual UTTCs may exist for many hours as an only 200–300 m thick cloud layer just a few hundred meters below the tropical cold point tropopause, covering up to 105 km2. With temperatures as low as 181 K these clouds are prime representatives for defining the water mixing ratio of air entering the lower stratosphere. Y1 - 2003 UR - http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/29275 UR - https://nbn-resolving.org/urn:nbn:de:hebis:30:3-292752 UR - http://www.atmos-chem-phys.org/acpd/3/1557/ SN - 1680-7367 SN - 1680-7375 N1 - © Author(s) 2003. This work is licensed under a Creative Commons License. VL - 3 SP - 1557 EP - 1578 PB - European Geosciences Union CY - Katlenburg-Lindau ER -