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Radiative Forcing by ContrailsA parametric study of the instantaneous radiative impact of contrails is presented using three different radiative transfer models for a series of model atmospheres and cloud parameters. Contrails are treated as geometrically and optically thin plane parallel homogeneous cirrus layers in a static atmospheres The ice water content is varied as a function of ambient temperature. The model atmospheres include tropical, mid-latitude, and subarctic summer and winter atmospheres Optically thin contrails cause a positive net forcing at top of the atmosphere. At the surface the radiative forcing is negative during daytime. The forcing increases with the optical depth and the amount of contrail cover. At the top of the atmosphere a mean contrail cover of 0.1% with average optical depth of 0.2 to 0.5 causes about 0.01 to 0.03 W/m(exp 2)a daily mean instantaneous radiative forcing. Contrails cool the surface during the day and heat the surface during the night, and hence reduce the daily temperature amplitude The net effect depends strongly on the daily variation of contrail cloud cover. The indirect radiative forcing due to particle changes in natural cirrus clouds may be of the same magnitude as the direct one due to additional cover.
Document ID
19990115889
Acquisition Source
Langley Research Center
Document Type
Reprint (Version printed in journal)
Authors
Meerkoetter, R.
(Deutsche Forschungsanstalt fuer Luft- und Raumfahrt Wessling, Germany)
Schumann, U.
(Deutsche Forschungsanstalt fuer Luft- und Raumfahrt Wessling, Germany)
Doelling, D. R.
(NASA Langley Research Center Hampton, VA United States)
Nakajima, T.
(Tokyo Univ. Japan)
Tsushima, Y.
(Tokyo Univ. Japan)
Date Acquired
August 19, 2013
Publication Date
January 1, 1999
Publication Information
Publication: Annales Geophysicae
Publisher: Springer-Verlag
Volume: 17
Subject Category
Meteorology And Climatology
Distribution Limits
Public
Copyright
Other

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