Ultrathin Tropical Tropopause Clouds (UTTCs): I. cloud morphology and occurrence

Th. Peter, B.P. Luo, M. Wirth, C. Kiemle, H. Flentje, V.A. Yushkov, V. Khattatov, V. Rudakov, A. Thomas, S. Borrmann, G. Toci, P. Mazzinghi, J. Beuermann, C. Schiller, F. Cairo, G. Di Donfrancesco, A. Adriani, C.M. Volk, J. Strom, K. NooneV. Mitev, R.A. MacKenzie, K.S. Carslaw, T. Trautmann, V. Santacesaria, L. Stefanutti

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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 200-300m thick cloud layer just a few hundred meters below the tropical cold point tropopause covering up to 105km2. With temperatures as low as 181K these clouds are prime representatives for defining the water mixing ratio of air entering the lower stratosphere. © 2003 European Geosciences Union.
Original languageEnglish
Pages (from-to)1083 - 1091
Number of pages9
JournalAtmospheric Chemistry and Physics
Issue number4
Publication statusPublished - 2003
Externally publishedYes


All Science Journal Classification (ASJC) codes

  • Atmospheric Science

Cite this

Peter, T., Luo, B. P., Wirth, M., Kiemle, C., Flentje, H., Yushkov, V. A., ... Stefanutti, L. (2003). Ultrathin Tropical Tropopause Clouds (UTTCs): I. cloud morphology and occurrence. Atmospheric Chemistry and Physics, 3(4), 1083 - 1091. https://doi.org/10.5194/acp-3-1083-2003