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 Earths atmosphere. Individual UTTCs may exist for many hours as an only 200300m thick cloud layer just a few hundred meters below the tropical cold point tropopause, covering up to 10^5 km2. With temperatures as low as 181K these clouds are prime representatives for defining the water mixing ratio of air entering the lower stratosphere.
Ultrathin Tropical Tropopause Clouds (UTTCs): I. Cloud Morphology and Occurrence
Toci G;Stefanutti L;
2003
Abstract
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 Earths atmosphere. Individual UTTCs may exist for many hours as an only 200300m thick cloud layer just a few hundred meters below the tropical cold point tropopause, covering up to 10^5 km2. With temperatures as low as 181K these clouds are prime representatives for defining the water mixing ratio of air entering the lower stratosphere.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
