Ultrathin Tropical Tropopause Clouds (UTTCs): II. Stabilization mechanisms
Year: 2003
Authors: Luo B.P., Peter T., Wernli H., Fueglistaler S., Wirth M., Kiemle C., Flentje H., Yushkov V.A., Khattatov V., Rudakov V., Thomas A., Borrmann S., Toci G., Mazzinghi P., Beuermann J., Schiller C., Cairo F., Di Don-Francesco G., Adriani A., Volk C.M., Strom J., Noone K., Mitev V., MacKenzie RA., Carslaw KS., Trautmann T., Santacesaria V., Stefanutti L.
Autors Affiliation: Institute for Atmospheric and Climate Science, ETH Zurich, Switzerland;
Institute for Atmospheric Physics, DLR Oberpfaffenhofen, Germany;
Central Aerological Observatory, Moscow, Russia;
Institute for Atmospheric Physics, University of Mainz, Germany;
Quantum Electronics Institute National Research Council (IEQ-CNR) Florence, Italy;
Istituto Nazionale di Ottica Applicata, Largo E. Fermi 6, 50125 Firenze, Italy;
Institute I: Stratosphere, Forschungszentrum Jülich GmbH, Jülich, Germany;
Institute for Atmospheric Science and Climate, CNR, Roma, Italy;
ENEA Casaccia, Rome, Italy;
Institut fr Meteorologie und Geophysik, Universität Frankfurt, Germany;
Institute of Applied Environmental Research, Stockholm University, Sweden;
Department of Meteorology, Stockholm University, Sweden;
Observatoire Cantonal, Neuchâtel, Switzerland;
Environmental Science Department, Lancaster University, UK;
School of the Environmental, University of Leeds, UK;
Institute of Meteorology, University of Leipzig, Germany;
IROE – CNR Nello Carrara, Firenze, Italy;
Geophysica-GEIE – CNR, Firenze, Italy
Abstract: Mechanisms by which subvisible cirrus clouds (SVCs) might contribute to dehydration close to the tropical tropopause are not well understood. Recently Ultrathin Tropical Tropopause Clouds (UTTCs) with optical depths around 10(-4) have been detected in the western Indian ocean. These clouds cover thousands of square kilometers as 200-300 m thick distinct and homogeneous layer just below the tropical tropopause. In their condensed phase UTTCs contain only 1-5% of the total water, and essentially no nitric acid. A new cloud stabilization mechanism is required to explain this small fraction of the condensed water content in the clouds and their small vertical thickness. This work suggests a mechanism, which forces the particles into a thin layer, based on upwelling of the air of some mm/s to balance the ice particles, supersaturation with respect to ice above and subsaturation below the UTTC. In situ measurements suggest that these requirements are fulfilled. The basic physical properties of this mechanism are explored by means of a single particle model. Comprehensive 1-D cloud simulations demonstrate this stabilization mechanism to be robust against rapid temperature fluctuations of +/-0.5 K. However, rapid warming (DeltaT>2 K) leads to evaporation of the UTTC, while rapid cooling (DeltaT<2 K) leads to destabilization of the particles with the potential for significant dehydration below the cloud. Journal/Review: ATMOSPHERIC CHEMISTRY AND PHYSICS
Volume: 3 Pages from: 1093 to: 1100
KeyWords: Stratosphere; Tropopause; Stratospheric water; Cirrus; DehydrationDOI: 10.5194/acp-3-1093-2003Citations: 28data from “WEB OF SCIENCE” (of Thomson Reuters) are update at: 2024-11-17References taken from IsiWeb of Knowledge: (subscribers only)Connecting to view paper tab on IsiWeb: Click hereConnecting to view citations from IsiWeb: Click here