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.
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