Atmospheric water-vapour profiling from passive microwave sounders over ocean and land. Part II: Validation using existing instruments

Authors

  • Frédéric Bernardo,

    1. Laboratoire de Météorologie Dynamique/IPSL/CNRS, Université de Paris VI/Jussieu, Paris, France
    2. Estellus, Paris, France
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  • Filipe Aires,

    Corresponding author
    1. Laboratoire de Météorologie Dynamique/IPSL/CNRS, Université de Paris VI/Jussieu, Paris, France
    2. Estellus, Paris, France
    3. Laboratoire de l'Etude du Rayonnement et de la Matière en Astrophysique, CNRS, Observatoire de Paris, France
    • CNRS/IPSL, Laboratoire de Météorologie Dynamique, UPMC, case 99, 4 place Jussieu, 75222 Paris, France.
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  • Catherine Prigent

    1. Laboratoire de l'Etude du Rayonnement et de la Matière en Astrophysique, CNRS, Observatoire de Paris, France
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Abstract

In a companion article (Paper I), a water-vapour retrieval algorithm has been developed using microwave sounding observations. An operational chain derived from this algorithm is being used for the Megha-Tropiques mission, launched in autumn 2011. The water vapour is retrieved for clear and cloudy scenes, excluding precipitation cases, over ocean and land surfaces. By-products are also calculated by the algorithm, including surface temperature and microwave emissivities over land.

Evaluation of the water-vapour products is the main objective of this article. The algorithm is tested using the HSB/AMSR-E (resp. MHS/AMSU-A) instruments on board the AQUA (resp. MetOp) platform, over the Tropics between ±30° in latitude. Results are compared with European Centre for Medium-Range Weather Forecasts (ECMWF) analyses and data from radiosondes. The root-mean-square error for the total column water vapour is ∼5 kg m2 for both clear and cloudy scenes, compared with radiosondes over land. The atmospheric water-vapour profile is retrieved for six atmospheric layers and the root-mean-square error is estimated to be lower than 20% in relative humidity, even for the lowest atmospheric layer over land. A posteriori validation tests on the brightness temperatures indicate an overall positive impact of the retrievals relative to a priori ECMWF analyses. Copyright © 2012 Royal Meteorological Society

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