Open AccessAfrican and Atlantic short-term climatic variations described from Meteosat water vapor channel
Author(s) -
Laurence Picon,
Siméon Fongang,
Geneviève Sèze,
M. Des̄bois
Publication year - 1995
Publication title -
annales geophysicae
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.522
H-Index - 93
eISSN - 1432-0576
pISSN - 0992-7689
DOI - 10.1007/s00585-995-0768-6
Subject(s) - intertropical convergence zone , water vapor , troposphere , environmental science , climatology , subtropics , cloud cover , subsidence , brightness , subtropical ridge , brightness temperature , geology , atmospheric sciences , meteorology , geography , cloud computing , precipitation , paleontology , physics , structural basin , fishery , computer science , optics , biology , operating system
Pluriannual series of Meteosat-2 water vapor(WV) images are used to build average maps of decadal and monthly brightnesstemperatures in the 6.3 µm channel. This processing is applied to all the3-hourly scenes, clear or cloudy, for July 1983 to July 1987. The ISCCPcloudiness analyses confirm that the warmest spots in the monthly WV imagescorrespond to scenes either clear or covered with low clouds, whereas thecoldest areas correspond to scenes where cloud tops above 440 hPa frequentlyoccur. The WV statistics are then used to characterize seasonal and interannualvariations of both the ITCZ (InterTropical Convergence Zone) and the warm (dry)areas, corresponding to subtropical subsidence. Thanks mainly to the seasonalvariations, relationships between the variations in the ITCZ and in drysubtropical areas can be studied. It is shown that, for the Meteosat sector, awetter subtropical high troposphere is associated with an enhanced activity ofthe ITCZ, and vice versa. For this area where the north-south assymetry islarge, the negative water vapor feedback previously proposed seems not to occur