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| Titel |
1D-Var retrieval of daytime total columnar water vapour from MERIS measurements |
| VerfasserIn |
R. Lindstrot, R. Preusker, H. Diedrich, L. Doppler, R. Bennartz, J. Fischer |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 5, no. 3 ; Nr. 5, no. 3 (2012-03-27), S.631-646 |
| Datensatznummer |
250002635
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| Publikation (Nr.) |
 copernicus.org/amt-5-631-2012.pdf |
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| Zusammenfassung |
| A new scheme for the retrieval of total columnar
water vapour from measurements of MERIS (Medium Resolution Imaging
Spectrometer) on ENVISAT (ENVIronmental SATellite) is presented. The
algorithm is based on a fast forward model of the water vapour transmittance
around 900nm, including a correction for atmospheric scattering and
the influence of the temperature- and pressure-profile on the water
vapour absorption lines. It provides the water vapour column amount
for cloud-free scenes above land and ocean at a spatial resolution
of 0.25 km × 0.3 km and 1 km × 1.2 km, depending on whether
applied to the "full resolution" or the operational "reduced
resolution" mode of MERIS. Uncertainties are provided on a pixel-by-pixel
basis, taking into account all relevant sources of error. An extensive
validation against various sources of ground-based reference data
reveals a high accuracy of MERIS water vapour above land (root mean
square deviations between 1.4 mm and 3.7 mm), apart from a wet
bias of MERIS between 5 and 10% that is found in all comparison studies.
This wet bias might be caused by spectroscopic uncertainties, such
as the description of the water vapour continuum. Above ocean the
accuracy is reduced, due to the uncertainty introduced by the unknown
atmospheric scattering. Consequently, an increased root mean square
deviation of ≥5 mm was found by comparing MERIS total
columnar water vapour above ocean against SSM/I and ENVISAT MWR data.
An increased wet bias of 2–3 mm is found over ocean, potentially
due to a not properly working atmospheric correction scheme. |
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