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Proceedings Paper

Upper tropospheric humidity and wind fields observed with the Meteosat water vapor channel
Author(s): Leopold Van de Berg; John Whitlock; Carlos Geijo; Johannes Schmetz
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Paper Abstract

In recent years the concern about the impact of the most important greenhouse gas, atmospheric water vapor, on the earth's climate was a driving force for many scientific projects. As the attention on atmospheric water vapor increased, the need for global, accurate and consistent data sets over long periods increased simultaneously. Satellites provide an ideal platform for such observations. For the geostationary satellite Meteosat the requirements of global and consistent measurements are certainly fulfilled, though the accuracy could be subject to improvement. When working with satellite data quantitatively an accurate calibration of the data is essential. Since a direct, on board calibration of Meteosat satellite imagery is not possible, a vicarious calibration is necessary. The calibration of the Meteosat water vapor channel is performed using information from radiosonde ascents. Changes in the operational calibration method implemented on the 4th February 1994 yield a more accurate and stable calibration. The water vapor channel is used operationally to retrieve humidity information within the upper troposphere. Within the relevant layer (600 - 300 hPa) a mean relative humidity is derived. Such product may be used in the initialization of numerical forecast models, in the validation of short- and long-term models and in eliminate monitoring of the upper-tropospheric humidity. Monthly averages of the Upper Tropospheric Humidity (UTH) fields reveal a relationship to the large-scale global circulation. Four times a day cloud motion vectors are determined from Meteosat water vapor imagery. The individual fields show the local wind distribution at a given time. Yet, the monthly mean of such wind fields reveal distributions on larger time and space scales. The divergence field from such a monthly mean wind field shows a correlation with the mean UTH field indicating that the UTH is largely determined by the large-scale atmospheric dynamics.

Paper Details

Date Published: 23 December 1994
PDF: 8 pages
Proc. SPIE 2309, Passive Infrared Remote Sensing of Clouds and the Atmosphere II, (23 December 1994); doi: 10.1117/12.196685
Show Author Affiliations
Leopold Van de Berg, European Space Agency/ESOC (Germany)
John Whitlock, European Space Agency/ESOC (Germany)
Carlos Geijo, European Space Agency/ESOC (Germany)
Johannes Schmetz, European Space Agency/ESOC (Germany)

Published in SPIE Proceedings Vol. 2309:
Passive Infrared Remote Sensing of Clouds and the Atmosphere II
David K. Lynch, Editor(s)

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