27 December 1995 Relationships between Meteosat-2 water-vapor radiances and large-scale climatic features
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Abstract
Statistics of brightness temperatures from the water vapor (WV) band channel of Meteosat 2 (5.7- 7. 1pm) from July 1983 through July 1987 are analyzed. All measurements (clearor not) are used to produce monthly and lOday averages. The ISCCP cloudiness retrieval is used to assess the cloud influence on the monthly WV brightness temperatures. The regional repartition and the interannual variations of different cloud types are compared with the global WV brightness temperatures. The main problem is the scattered presence of very thin clouds. But generally speaking, the warmest spots in monthly WV images are related with clear or low cloudy skies while the coldest areas correspond to clouds whose top is above 440 hPa. To confirm these results, a clear sky image has been synthetised using a cloud clearing algorithm. The WV statistics are then used to characterize seasonal and interannual variations of both the ITCZ (coldest spots) and the subtropical subsidence areas (warmest spots). Because the seasonal variations of both phenomena are generally larger than their interannual changes, the seasonal cycle of WV radiances is used to study relationships between the intensity and the extension of the ITCZ compared to the dry subtropical areas. It is shown that, for the Meteosat sector, a wetter subtropical high troposphere is associated with an enhanced activity of the JTCZ, and vive-versa. This result seems to indicate a positive water vapor feedback in this particular region.
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L. Picon, L. Picon, Genevieve M. Seze, Genevieve M. Seze, Michel Desbois, Michel Desbois, C. Huet, C. Huet, "Relationships between Meteosat-2 water-vapor radiances and large-scale climatic features", Proc. SPIE 2578, Passive Infrared Remote Sensing of Clouds and the Atmosphere III, (27 December 1995); doi: 10.1117/12.228945; https://doi.org/10.1117/12.228945
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