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Ice supersaturation in the ECMWF integrated forecast system

Tompkins, Adrian M. and Gierens, Klaus and Rädel, Gaby (2007) Ice supersaturation in the ECMWF integrated forecast system. Quarterly Journal of the Royal Meteorological Society, 133, pp. 53-63. DOI: 10.1002/qj.14.

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Official URL: http://www.interscience.wiley.com

Abstract

A parametrization for ice supersaturation is introduced into the ECMWF Integrated Forecast System (IFS), compatible with the cloud scheme that allows partial cloud coverage. It is based on the simple, but often justifiable, diagnostic assumption that the ice nucleation and subsequent depositional growth time-scales are short compared to the model time step, thus supersaturation is only permitted in the clear-sky portion of the grid cell. Results from model integrations using the new scheme are presented, which is demonstrated to increase upper-tropospheric humidity, decrease high-level cloud cover and, to a much lesser extent, cloud ice amounts, all as expected from simple arguments. Evaluation of the relative distribution of supersaturated humidity amounts shows good agreement with the observed climatology derived from in situ aircraft observations. With the new scheme, the global distribution of frequency of occurrence of supersaturated regions compares well with remotely sensed microwave limb sounder (MLS) data, with the most marked errors of underprediction occurring in regions where the model is known to underpredict deep convection. Finally, it is also demonstrated that the new scheme leads to improved predictions of permanent contrail cloud over southern England, which indirectly implies upper-tropospheric humidity fields are better represented for this region.

Document Type:Article
Title:Ice supersaturation in the ECMWF integrated forecast system
Authors:
AuthorsInstitution or Email of Authors
Tompkins, Adrian M.ECMWF, Reading, UK
Gierens, KlausUNSPECIFIED
Rädel, GabyUniv. Reading, Reading, UK
Date:22 February 2007
Journal or Publication Title:Quarterly Journal of the Royal Meteorological Society
Refereed publication:Yes
In Open Access:No
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:133
DOI:10.1002/qj.14
Page Range:pp. 53-63
Status:Published
Keywords:cirrus clouds, ice nucleation, microphysics
HGF - Research field:Aeronautics, Space and Transport (old)
HGF - Program:Space (old)
HGF - Program Themes:W EO - Erdbeobachtung
DLR - Research area:Space
DLR - Program:W EO - Erdbeobachtung
DLR - Research theme (Project):W - Vorhaben Atmosphären- und Klimaforschung (old)
Location: Oberpfaffenhofen
Institutes and Institutions:Institute of Atmospheric Physics > Atmospheric Dynamics
Deposited By: Dr.rer.nat. Klaus Martin Gierens
Deposited On:08 Mar 2007
Last Modified:20 Oct 2014 14:31

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