 |
| Titel |
Ultrathin Tropical Tropopause Clouds (UTTCs): II. Stabilization mechanisms |
| VerfasserIn |
B. P. Luo, Th. Peter, H. Wernli, S. Fueglistaler, 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. Don-Francesco, A. Adriani, C. M. Volk, J. Ström, K. Noone, V. Mitev, R. A. MacKenzie, K. S. Carslaw, T. Trautmann, V. Santacesaria, L. Stefanutti |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 3, no. 4 ; Nr. 3, no. 4 (2003-07-29), S.1093-1100 |
| Datensatznummer |
250001141
|
| Publikation (Nr.) |
 copernicus.org/acp-3-1093-2003.pdf |
|
|
|
|
|
| Zusammenfassung |
| 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 (\Delta T > 2 K) leads to evaporation of the
UTTC, while rapid cooling (\Delta T < -2 K) leads to destabilization of the particles with the potential
for significant dehydration below the cloud |
| |
|
| Teil von |
|
|
|
|
|
|
|
|