547 
7- CONCLUSION 
In this study, we have proposed a new algorithm to estimate die columnar water vapour content from ATSR/IR 
Split-Window channels. The simultaneous measurements of die ATSR/MW radiometer permit us to fit the 
algorithm over oceans areas. The algorithm has then been validated on a dataset containing 35 ATSR images. 
The application show a good agreement between the infrared methodology and the microwave 
measurement with standard deviation less than 0.4 g/cm 2 - This work has now to be pursued at a global scale on 
a larger dataset to test the effects of the local conditions : atmospheric temperature, surface wind speed 
influencing the surface emissivity, for example. Then, it may be applied over land where the surface 
emissivity effects should be carefully analysed. 
In conclusion, diese very preliminary results show that die Split-Window transmittance ratio technique 
seems very promising to estimate the total précipitable water with ATSR/IR data, and that the accuracy 
obtained is sufficient to improve the Split-Window algorithms for surface temperature determination. 
Acknowledgements 
The authors would like to thank D. Vidal-Madjar for fruitful discussions and also all the members of 
the RAL team who provided us with the ATSR data. This work has been supported by CNRS and ESA. 
8 - REFERENCES 
Becker, F„ 1987 : The impact of spectral emissivity on the measurement of land surface temperature from a 
satellite, Int. J. Remote Sen., 8, 1509-1522. 
Becker F. and Z.L.Li, 1990 : Towards a local Split-Window mediod over land surface, Int. J. Remote Sens. 
3:369-393. 
Bernard, R., A. LeComec, L. Eymard and L. Tabary, 1994 : The microwave radiometer on-board ERS1. 
Part 1 : Characterisdcs and performances, to be published in IEEE Trans. Geosc. Remote Sensing. 
ERS-1 Reference manual, 1989 : Technical note, ESA, DC-MA-EOS-ED-OOOl. 
Eymard, L. , L. Tabary and A. LeComec, 1992 : Validation of the ATSR/M microwave radiometer data. 
Proceedings of the First ERS1 Symposium. Space at the Service of our Environment, 4-6 November 1992, 
Cannes, France, 763-766. 
Eymard, L., L. Tabary and A. LeComec, 1994 : The microwave radiometer aboard ERS1. Part 2 : Validation of 
the geophysical products, submitted to IEEE Trans. Geosc. Remote Sensing. 
François, C. and C. Otüé, 1994 : Comparison of different atmospheric corrections algorithms with the ATSR- 
ERS1 Infrared radiometer, Proceedings of the 6di Symposium on "Physical measurements and Signatures in 
Remote Sensing, 17-21 January, Val d'Isère, France. 
Harris, A.R. and I.M.Mason, 1992 : An extension to the split-window technique giving improved atmospheric 
correction and total water vapour, Int. J. Remote Sensing, 5, 881-892. 
Jedlovec G.J., 1990 : Précipitable water estimation from high-resolution Split-Window radiance measurements. 
J. of Appl. Meteor, 29, 863-877. 
Kleespies, T.J. and L. M. McMillin, 1990 : Retrieval of précipitable water from observations in the Split- 
Window over varying surface temperatures., J. Appl. Meteor., 29, 851-862. 
Li Z.L. and F. Becker, 1993 : Feasibility of Land Surface Temperature and Emissivity determination from 
AVHRR data . Remote Sens. Environ. 43:67-85 
Lojou, J.Y., R. Bernard and L. Eymard, 1994 : A simple method for testing brightness temperatures from 
satellite microwave radiometers, to be published in J. Atmos. Oceanic Tech. 
Ottlé, C„ and Vidal-Madjar, D„ 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, R. W. and K. T. Kriebel, 1988 : An improved method for detecting clear sky and cloudy radiances 
from AVHRR data, Int. J. Remote Sensing, 15, 2873-2886. 
Scott, N.A. and A. Chédin, 1981 : A fast line by line mediod for Atmospheric Absorption Computadons : The 
Automatized Atmospheric Absorption Adas., J. Appl. Meteor., 20:802-812. 
Sobrino, J.A., C. Coll and V. Caselles ,1991 : Atmospheric correcdon for land surface temperature using 
NOAA11 AVHRR channels 4 and 5. Remote Sens. Environ. 38, 19-34. 
Sobrino, J. A., Z. L. Li, M. Ph. Stoll and F. Becker, 1994 : Improvements in the Split-Window technique for 
land surface temperature determination, to be published in IEEE Trans. Geosc. Remote Sensing, 
ulivieri, C., M.M. Castronuevo, R. Francioni and A. Cardillo ,1993 : A Split-Window algorithm for 
estimating land surface temperature from satellites. To be published in Remote Sens. Environ.