64 
datasets. When no water vapor data is available the inaccuracy in the retrieved temperature is in fact 
more crucial for land data (up to 6 K) and mean climatic SW coefficients should not be used for accurate 
temperature retrievals. Consequently the determination of the water vapor content is necessary. 
Therefore, the possibility to determine W from space, using the Split-Window variance method for 
instance, has now to be investigated. 
For SST measurements the Double-Viewing method seems to be a valuable first approach giving 
good results when no other data than Nadir and Forward satellite temperatures are available. According 
to the simulation, the Double-Viewing method (which does not necessitate any ancillary information in 
its accurate and simplified version) is supposed to give SST with a bias lower than 0.5 K when the water 
vapor amount is lower than 3 g/cm^. Both applications with ATSR data show actually a mean error lower 
than this simulated value (either when compared with ground truth data or with Lowtran7 retrieved 
temperature). Further studies have to be done for LST retrieval because it proves difficult to derive a 
straightforward LST double-viewing method. 
Acknowledgements 
We would like to thanks Noelle Scott for providing us with the TIGR dataset and the 4A 
program, and for fruitful discussions. We are grateful to Xingfa Gu who provided us with the CRAU92 
data, to I. J. Barton who provided us with the Coral Sea data and also to RAL for the other ATSR data. 
5 - REFERENCES 
Achard, V. (1991), Trois problèmes clés de l'analyse 3D de la structure thermodynamique de 
l’atmosphère par satellite : mesure du contenu en ozone; classification des masses d'air; modélisation 
"hyper" rapide du transfert radiatif, Thèse de l'université Paris 7, pp 44-58. 
Barton, IJ. (1993) Personal Communication, Division of Atmospheric Research, CSIRO, Aspendale, 
Victoria, Australia 
Becker, F. and Z.L. Li (1990), Towards a local Split-Window method over land surface, Int. J. Remote 
Sensing, 3:369-393. 
Chedin, A., Scott, N. A., and Berroir, A. (1982), A single-channel, double-viewing angle method for sea 
surface temperature determination from coincident METEOS AT and TIROS-N radiometric 
measurements, J. Appl. Meteor., 21:613-618 
François, C. and C. Ottlé, (1992), Estimation of the angular variation of the sea surface emissivity with 
the ATSR/ERS-1 data., to be published in Remote Sens. Environ. 
Gu, X. and B. Séguin (1993), Evaluation of atmospherically corrected surface temperature measured by 
ERS1-ATSR, NOAA11-AVHRR and LANDSAT-TM sensors., Proc. of the workshop on Thermal 
Remote Sensing of the Energy and Water balance over vegetation in cunjunction with other sensors, La 
Londe Les Maures, France, 20-23 September 1993. 
Harris, A.R., Mason, I.M. (1992), An extension to the split-window technique giving improved 
atmospheric correction and total water vapour, Int. J. Remote Sensing, 5:881-892. 
Kneizys, F. X„ Shettle, E. P„ Abreu, L. W„ Anderson, G. P., Chetwynd, J. H„ Gallery, W. 0., Selby, J. 
E. A., and Clough, S. A. (1989), Atmospheric transmittance/radiance: the LOWTRAN 7 model. 
Masuda, K., Takashima, T., and Takayama, Y. (1988), Emissivity of pure and sea waters for the model 
sea surface in the infrared window regions, Remote Sens. Environ., 24:313-329. 
McMillin, L. M. (1975), Estimation of sea surface temperatures from two infrared window measurements 
with different absorption., J. Geophys. Res., 80:5113-5117. 
Ottlé, C. and D. Vidal-Madjar (1992), Estimation of land surface temperature with NOAA9 data, Remote 
Sens. Environ., 40:27-41. 
Praia, A. J. (1993), Land surface temperatures derived from the AVHRR and the ATSR. Part 1 : Theory, 
J. Geophys. Res., 98D9:16,689-16,702. 
Saunders, P. M., and A. Chédin (1967), Aerial measurements of sea surface temperature in the infrared., 
J. Geophys. Res., 72:4109-4117. 
Scott, N.A. and A. Chédin (1981), A fast line by line method for Atmospheric Absorption Computations 
: The Automatized Atmospheric Absorption Adas., J. Appl. Meteor., 20:802-812. 
Sobrino, J.A., Coll, C. and V. Caselles (1991), Atmospheric correction for land surface temperature using 
NOAA11 AVHRR channels 4 and 5, Remote Sens. Environ., 38:19-34.