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| Titel |
Description and validation of an AOT product over land at the 0.6 μm channel of the SEVIRI sensor onboard MSG |
| VerfasserIn |
E. Bernard, C. Moulin, D. Ramon, D. Jolivet, J. Riedi, J.-M. Nicolas |
| 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 ; 4, no. 11 ; Nr. 4, no. 11 (2011-11-25), S.2543-2565 |
| Datensatznummer |
250002140
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| Publikation (Nr.) |
 copernicus.org/amt-4-2543-2011.pdf |
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| Zusammenfassung |
The Spinning Enhanced Visible and InfraRed Imager (SEVIRI) aboard Meteosat
Second Generation (MSG) launched in 2003 by EUMETSAT is dedicated to the
Nowcasting applications and Numerical Weather Prediction and to the provision
of observations for climate monitoring and research. We use the data in
visible and near infrared (NIR) channels to derive the aerosol optical
thickness (AOT) over land. The algorithm is based on the assumption that the
top of the atmosphere (TOA) reflectance increases with the aerosol load. This
is a reasonable assumption except in case of absorbing aerosols above bright
surfaces. We assume that the minimum in a 14-days time series of the TOA
reflectance is, once corrected from gaseous scattering and absorption,
representative of the surface reflectance. The AOT and the aerosol model (a
set of 5 models is used), are retrieved by matching the simulated TOA
reflectance with the TOA reflectances measured by SEVIRI in its visible and
NIR spectral bands.
The high temporal resolution of the data acquisition by SEVIRI allows to
retrieve the AOT every 15 min with a spatial resolution of 3 km at
sub-satellite point, over the entire SEVIRI disk covering Europe, Africa and
part of South America. The resulting AOT, a level 2 product at the native
temporal and spatial SEVIRI resolutions, is presented and evaluated in this
paper.
The AOT has been validated using ground based measurements from AErosol
RObotic NETwork (AERONET), a sun-photometer network, focusing over Europe for
3 months in 2006. The SEVIRI estimates correlate well with the AERONET
measurements, r = 0.64, with a slight overestimate, bias = −0.017.
The sources of errors are mainly the cloud contamination and the bad
estimation of the surface reflectance. The temporal evolutions exhibited by
both datasets show very good agreement which allows to conclude that the AOT
Level 2 product from SEVIRI can be used to quantify the aerosol content and
to monitor its daily evolution with a high temporal frequency. The comparison
with daily maps of Moderate Resolution Imaging Spectroradiometer (MODIS) AOT
level 3 product shows qualitative good agreement in the retrieved geographic
patterns of AOT.
Given the high spatial and temporal resolutions obtained
with this approach, our results have clear potential for applications ranging
from air quality monitoring to climate studies. This paper presents a first
evaluation and validation of the derived AOT over Europe in order to document
the overall quality of a product that will be made publicly available to the
users of the aforementioned research communities. |
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