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  • Author or Editor: M. M. Poc x
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M. M. Poc and M. Roulleau

Abstract

A quasi-operational process for the determination of water vapor fields from METEPSAT-1 water vapor channel data is described. Each count of the WV picture is replaced by the corresponding mean relative humidity value using both the calibration of the WV channel and the empirical relation between radiance and relative humidity. Midlatitude summer and tropical regions are examined.

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M. Roulleau and M. M. Poc

Abstract

A new kind of frost-point hygrometer has been developed for horizontal soundings of the lower stratosphere. The cooling source, using the radiative cooling of a blackbody during the night, is able to cool the mirror down to −90°C. The frost deposit is detected with an optical sensing unit associated with a regulating loop controlling the mirror heating to keep the frost thickness constant. The equipment is presented and described and the results of the first flight performed in 1976 are given and discussed.

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M. M. Poc, M. Roulleau, N. A. Scott, and A. Chedin

Abstract

In this paper, quantitative studies of water vapor Meteosat imagery, based on an accurate transmittance and radiance model are described. Using conventional radiosonde data, a linear relation between cloudless radiances and digital counts is obtained. It is shown that the distribution with altitude of the peak contribution to the radiances varies from about the 550 mb level to about the 450 mb level for pictures acquired in July over the western part of Europe and Mediterranean Sea. The influence of the temperature profile on the altitude of the maximum contribution layer is pointed out. A relation between the radiative field and the water vapor mass above the 600 mb level is found.

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