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| Titel |
A multi-site intercomparison of integrated water vapour observations for climate change analysis |
| VerfasserIn |
R. Malderen, H. Brenot, E. Pottiaux, S. Beirle, C. Hermans, M. Mazière, T. Wagner, H. Backer, C. Bruyninx |
| 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 ; 7, no. 8 ; Nr. 7, no. 8 (2014-08-13), S.2487-2512 |
| Datensatznummer |
250115870
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| Publikation (Nr.) |
 copernicus.org/amt-7-2487-2014.pdf |
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| Zusammenfassung |
Water vapour plays a dominant role in the climate
change debate. However, observing water vapour over a climatological time
period in a consistent and homogeneous manner is challenging. On one hand,
networks of ground-based instruments able to retrieve homogeneous integrated
water vapour (IWV) data sets are being set up. Typical examples are Global
Navigation Satellite System (GNSS) observation networks such as the
International GNSS Service (IGS), with continuous GPS (Global Positioning
System) observations spanning over the last 15+ years, and the AErosol
RObotic NETwork (AERONET), providing long-term observations performed with
standardized and well-calibrated sun photometers. On the other hand,
satellite-based measurements of IWV already have a time span of over 10 years
(e.g. AIRS) or are being merged to create long-term time series (e.g. GOME,
SCIAMACHY, and GOME-2).
This study performs an intercomparison of IWV measurements from satellite
devices (in the visible, GOME/SCIAMACHY/GOME-2, and in the thermal infrared,
AIRS), in situ measurements (radiosondes) and ground-based instruments (GPS,
sun photometer), to assess their use in water vapour trends analysis. To this
end, we selected 28 sites world-wide for which GPS observations can directly
be compared with coincident satellite IWV observations, together with sun
photometer and/or radiosonde measurements. The mean biases of the different
techniques compared to the GPS estimates vary only between −0.3 to 0.5 mm
of IWV. Nevertheless these small biases are accompanied by large standard
deviations (SD), especially for the satellite instruments. In particular, we
analysed the impact of clouds on the IWV agreement. The influence of specific
issues for each instrument on the intercomparison is also investigated (e.g.
the distance between the satellite ground pixel centre and the co-located
ground-based station, the satellite scan angle, daytime/nighttime
differences). Furthermore, we checked if the properties of the IWV scatter
plots between these different instruments are dependent on the geography
and/or altitude of the station. For all considered instruments, the only
dependency clearly detected is with latitude: the SD of the IWV observations
with respect to the GPS IWV retrievals decreases with increasing latitude and
decreasing mean IWV. |
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