Dehydration potential of ultrathin clouds at the tropical tropopause

Year: 2003

Authors: Luo B. P., Peter T., Fueglistaler S., Wernli H., 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 Donfrancesco G., Adriani A., Volk C. M., Strom J., Noone K., Mitev V., MacKenzie R. A., Carslaw K. S., Trautmann T., Santacesaria V., Stefanutti L.

Autors Affiliation: Institute for Atmospheric and Climate Science, Swiss Federal Institute of Technology, Zurich, Switzerland; Institute for Atmospheric Physics, Deutches Zentrum für Luft- und Raumfahrt, Oberpfaffenhofen, Germany; Central Aerological Observatory, Moscow, Russia; Institute for Atmospheric Physics, University of Mainz, Mainz, Germany; Quantum Electronics Institute, Istituto di Elettronica Quantistica, Consiglio Nazionale delle Ricerche, Florence, Italy; National Institute of Applied Optics, Florence, Italy; Institute I: Stratosphere, Forschungszentrum Jülich, Jülich, Germany; Istituto di Fisica dell\’Atmosfera, Consiglio Nazionale delle Ricerche, Rome, Italy; Ente per le Nuove Tecnologie, l\’Energia e l\’Ambiente-Casaccia, Rome, Italy; Institut für Meteorologie und Geophysik, University of Frankfurt, Frankfurt, Germany;
Institute of Applied Environmental Research, Stockholm University, Stockholm, Sweden; Department of Meteorology, Stockholm University, Stockholm, Sweden; Observatoire Cantonal, Neuchâtel, Switzerland; Environmental Science Department, Lancaster University, Lancaster, UK; School of the Environment, University of Leeds, Leeds, UK; Institute of Meteorology, University of Leipzig, Leipzig, Germany; Istituto di Ricerca Onde Elettromagnetiche, Consiglio Nazionale delle Ricerche “Nello Carrara”, Firenze, Italy

Abstract: We report on the first simultaneous in situ and remote measurements of subvisible cirrus in the uppermost tropical troposphere. The observed cirrus, called UTTCs (ultrathin tropical tropopause clouds), are the geometrically (200-300 m) and optically (t ˜ 10-4) thinnest large-scale clouds ever sampled (˜105 km2). UTTCs consist of only a few ice particles per liter with mean radius ˜5 µm, containing only 1-5 % of the total water. Yet, brief adiabatic cooling events only 1-2 K below mean ambient temperature destabilize UTTCs, leading to large sedimenting particles (r ˜ 25 µm). Due to their extreme altitude above 17 km and low particle number density, UTTCs may efficiently dehydrate air during its last encounter with the ice phase before entering the stratosphere.

Journal/Review: GEOPHYSICAL RESEARCH LETTERS

Volume: 30 (11)      Pages from: 1557  to: 1557

KeyWords: Clouds; Dehydration; Ice; Sediments; Troposphere; Upper atmosphere, Ultrathin clouds, Geophysics, cirrus; cloud; cloud microphysics; dehydration; ice; tropopause
DOI: 10.1029/2002GL016737

ImpactFactor: 2.422
Citations: 47
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