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Clear Sky WV radiances Version imprimable

Rémy Roca, Hélène Brogniez and Laurence Picon
Laboratoire de Météorologie Dynamique
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Clear Sky Radiances

A long-term archive of clear-sky METEOSAT “water vapor” observations, covering the July 1983 – February 1997 period with a 3 hourly time step and a spatial resolution of 0.625° is made available for climate analysis. Access to the data.

Algorithm summary

Cloud clearing is performed using a scene selection procedure based on the International Satellite Cloud Climatology Project DX product. In this procedure low cloud scenes are kept due to the negligible contribution of the low atmospheric layer in this spectral band. Cloud contamination is shown to have little influence on the clear sky radiance (CSR) field and is mainly confined to the continental Inter-Tropical Convergence Zone with values less than 0.5K. This scene selection yields to a significantly enhanced sampling with respect to pure clear sky in the subtropical highs regions. Homogenization of the 14 years database is performed  and every radiances is expressed in METEOSAT-5 equivalent. A comparison to the operational radiosondes archive indicates a small bias of 0.3K that is stable throughout the period.  More details in the publications below.

Implementation and access

The individual files correspond to each year. The files contain all the available CSR with a time step of 3 hours. All the files are in netcDF.

Future works

We are currently extending the database coverage both in time and space thanks to the tech. support of the ICARE center.  The final product is likely to be extended up to 2005.

References

Brogniez H., Roca R. and L. Picon 2006 A new METEOSAT Water Vapor archive for climate studies. Part 2: clear sky radiances J. Geophys. Research, in revision (PDF)
Picon L, Roca R, S Serrar, JL Monge and M Desbois, 2003, A new METEOSAT water vapor archive for climate studies, J. Geophys Res., vol 108, D10,10.1029/2002JD002640. (PDF)

Acknowledgements

Thanks to the ARA team at LMD for sharing with us their version of the radiosondes archive and in particular to R. Armante and C. Stubenrauch for helpful discussions. The help of V. Golea (NASA/GISS) and G. Sèze (LMD) with the DX dataset are appreciated. We would like to thank F.M. Bréon (LSCE) for providing us the alternative calibration coefficients and for enriching discussions and J.N. Thépaut (ECMWF) for suggesting the comparison to the soundings archive. We thank also L. Van de Berg (EUMETSAT) for fruitful discussions along the course of the study. The support of K. Ramage and of the IPSL dataserver “Climserv” is also appreciated.

Dernière mise à jour : ( 07-04-2010 )
 
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