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Effects of three-dimensional photons transport on the radiative forcing of realistic contrails

Forster, Linda and Emde, Claudia and Mayer, Bernhard and Unterstrasser, Simon (2012) Effects of three-dimensional photons transport on the radiative forcing of realistic contrails. Journal of the Atmospheric Sciences, 69, pp. 2243-2255.

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Official URL: http://journals.ametsoc.org/doi/pdf/10.1175/JAS-D-11-0206.1

Abstract

Estimates of the global radiative forcing (RF) of line-shaped contrails and contrail cirrus exhibit a high level of uncertainty. In most cases, 1D radiative models have been used to determine the RF on a global scale. In this paper the effect of neglecting the 3D radiative effects of realistic contrails is quantified. Calculating the 3D effects of an idealized elliptical contrail as in the work of Gounou and Hogan with the 3D radiative transfer model MYSTIC (for ‘‘Monte Carlo code for the physically correct tracing of photons in cloudy atmospheres’’) produced comparable results: as in Gounou and Hogan’s work the 3D effect (i.e., the difference in RF between a 3Dcalculation and a 1Dapproximation) on contrail RF was on the order of 10% in the longwave and shortwave. The net 3D effect, however, can be much larger, since the shortwave and longwave RF largely cancel during the day. For the investigation of the 3D effects of more realistic contrails, the microphysical input was provided by simulations of a 2D contrail-to-cirrus large-eddy simulation (LES) model. To capture some of the real variability in contrail properties, this paper examines two contrail evolutions from 20 min up to 6 h in an environment with either high or no vertical wind shear. This study reveals that the 3D effects show a high variability under realistic conditions since they depend strongly on the optical properties and the evolutionary state of the contrails. The differences are especially large for low elevations of the sun and contrails spreading in a sheared environment. Thus, a parameterization of the 3D effects in climate models would need to consider both geometry and microphysics of the contrail.

Document Type:Article
Title:Effects of three-dimensional photons transport on the radiative forcing of realistic contrails
Authors:
AuthorsInstitution or Email of Authors
Forster, LindaLinda.Forster@physik.lmu.de
Emde, ClaudiaLMU
Mayer, BernhardLMU
Unterstrasser, Simonsimon.unterstrasser@dlr.de
Date:2012
Journal or Publication Title:Journal of the Atmospheric Sciences
Refereed publication:Yes
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:69
Page Range:pp. 2243-2255
Status:Published
Keywords:radiative forcing, contrail, contrail-cirrus, MYSTIC, Monte Carlo, 3d effects, contrail cluster
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:ATM and Operation
DLR - Research area:Aeronautics
DLR - Program:L AO - Air Traffic Management and Operation
DLR - Research theme (Project):L - Climate, Weather and Environment
Location: Oberpfaffenhofen
Institutes and Institutions:Institute of Atmospheric Physics > Atmospheric Dynamics
Deposited By: Jana Freund
Deposited On:30 Jul 2012 12:21
Last Modified:12 Dec 2013 21:44

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