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Parameterization of contrails in the UK Met Office Climate Model

Rap, A, Forster, PM, Jones, A, Boucher, O, Haywood, JM, Bellouin, N and De Leon, RR (2010) Parameterization of contrails in the UK Met Office Climate Model. Journal of Geophysical Research - Atmospheres, 115 (D10205). ISSN 0148-0227

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Abstract

Persistent contrails are believed to currently have a relatively small but significant positive radiative forcing on climate. With air travel predicted to continue its rapid growth over the coming years, the contrail warming effect on climate is expected to increase. Nevertheless, there remains a high level of uncertainty in the current estimates of contrail radiative forcing. Contrail formation depends mostly on the aircraft flying in cold and moist enough air masses. Most studies to date have relied on simple parameterizations using averaged meteorological conditions. In this paper we take into account the short-term variability in background cloudiness by developing an on-line contrail parameterization for the UK Met Office climate model. With this parameterization, we estimate that for the air traffic of year 2002 the global mean annual linear contrail coverage was approximately 0.11%. Assuming a global mean contrail optical depth of 0.2 or smaller and assuming hexagonal ice crystals, the corresponding contrail radiative forcing was calculated to be less than 10 mW m(-2) in all-sky conditions. We find that the natural cloud masking effect on contrails may be significantly higher than previously believed. This new result is explained by the fact that contrails seem to preferentially form in cloudy conditions, which ameliorates their overall climate impact by approximately 40%.

Item Type: Article
Copyright, Publisher and Additional Information: Reproduced in accordance with the publisher's self-archiving policy.
Keywords: GENERAL-CIRCULATION MODEL, LARGE-SCALE MODEL, CIRRUS CLOUDS, AVHRR-DATA, RADIATIVE PROPERTIES, IMPACT, SIMULATIONS, ATMOSPHERE, SOLAR, GCM
Institution: The University of Leeds
Academic Units: The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds)
Depositing User: Symplectic Publications
Date Deposited: 05 Sep 2011 15:24
Last Modified: 08 Feb 2013 17:33
Published Version: http://dx.doi.org/10.1029/2009JD012443
Status: Published
Publisher: AMER GEOPHYSICAL UNION
Refereed: Yes
Identification Number: 10.1029/2009JD012443
Related URLs:
URI: http://eprints.whiterose.ac.uk/id/eprint/43207

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