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| Titel |
Evaluation of upper tropospheric humidity forecasts from ECMWF using AIRS and CALIPSO data |
| VerfasserIn |
N. Lamquin, K. Gierens, C. J. Stubenrauch, R. Chatterjee |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 9, no. 5 ; Nr. 9, no. 5 (2009-03-10), S.1779-1793 |
| Datensatznummer |
250007012
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| Publikation (Nr.) |
 copernicus.org/acp-9-1779-2009.pdf |
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| Zusammenfassung |
| An evaluation of the upper tropospheric humidity from the European
Centre of Medium-Range Weather Forecasts (ECMWF) Integrated
Forecast System (IFS) is presented. We first make an analysis of the
spinup behaviour of ice supersaturation in weather forecasts. It
shows that a spinup period of at least 12 h is necessary before
using forecast humidity data from the upper troposphere. We compare
the forecasted upper tropospheric humidity with coincident relative
humidity fields retrieved from the Atmospheric InfraRed Sounder
(AIRS) and with cloud vertical profiles from the Cloud-Aerosol
Lidar and Infrared Pathfinder Satellite Observation (CALIPSO). The
analysis is made over one year, from October 2006 to September 2007,
and we discuss how relative humidity and cloud features appear both
in the IFS and in the observations. The comparison with AIRS
is made difficult because of the vertical resolution of the
sounder and the impossibility to retrieve humidity for high cloudiness.
Clear sky relative humidities show a rather good
correlation whereas cloudy situations reflect more the effect of a
dry bias for AIRS increasing with the relative humidity. The
comparison with CALIPSO shows that the IFS predicts high relative
humidity where CALIPSO finds high clouds, which supports the good
quality of the ECMWF upper tropospheric cloud forecast. In a last
part, we investigate the presence of ice supersaturation within low
vertical resolution pressure layers by comparing the IFS outputs for
high-resolution and low-resolution humidity profiles and by
simulating the interpolation of humidity over radiosonde data. A new
correction method is proposed and tested with these data. |
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