1995 .

(2 publications)

L. Picon, S. Fongang, G. Seze, and M. Desbois. African and Atlantic short-term climatic variations described from Meteosat water vapor channel. Annales Geophysicae, 13:768-781, July 1995. [ bib | DOI | ADS link ]

Pluriannual series of Meteosat-2 water vapor (WV) images are used to build average maps of decadal and monthly brightness temperatures in the 6.3 m channel. This processing is applied to all the 3-hourly scenes, clear or cloudy, for July 1983 to July 1987. The ISCCP cloudiness analyses confirm that the warmest spots in the monthly WV images correspond to scenes either clear or covered with low clouds, whereas the coldest areas correspond to scenes where cloud tops above 440 hPa frequently occur. The WV statistics are then used to characterize seasonal and interannual variations of both the ITCZ (InterTropical Convergence Zone) and the warm (dry) areas, corresponding to subtropical subsidence. Thanks mainly to the seasonal variations, relationships between the variations in the ITCZ and in dry subtropical areas can be studied. It is shown that, for the Meteosat sector, a wetter subtropical high troposphere is associated with an enhanced activity of the ITCZ, and vice versa. For this area where the north-south assymetry is large, the negative water vapor feedback previously proposed seems not to occur.

L. Picon and M. Desbois. High level moisture observations and derived parameters from METEOSAT and other geostationary satellites. Advances in Space Research, 16:73-86, 1995. [ bib | DOI | ADS link ]

This paper summarizes the interpretation and the main applications of the water vapor Meteosat channel. Some comparisons are made with GOES and GMS. The water vapor channel allows to detect the variations of the mid-tropospheric humidity between about 300 and 600 hPa over both sea and land. The upper tropospheric humidity operationaly producted by the ESOC is compared with humidity obtained from GOES data. The second kind of studies involves tropospheric dynamics. Results of the wind extraction method using the water vapor Meteosat data are shown. The usefulness of these data for the height assignment of cloud tracers and for the satellite rainfall estimation is also discussed. Finally some climatic studies performed with water vapor data are presented.