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Performance of two GCM borne radiation schemes in calculating contrail radiative forcing

Ponater, Michael and Frömming, Christine (2012) Performance of two GCM borne radiation schemes in calculating contrail radiative forcing. 3rd conference on Transport, Atmosphere, and Climate (TA3-3), 25-28 Jun 2012, Prien am Chiemsee, Germany.

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Abstract

Contrail radiative forcing is difficult to determine even if the numerous key parameters like coverage, ice water content, crystal size etc. are known. One reason is the considerable amount of cancellation between the positive (warming) component from the contrails' greenhouse effect and the negative (cooling) component from backscattering of solar irradiance. This sets high demands on the abilities of the radiative transfer model used to calculate the forcing, and a substantial respective uncertainty has been documented in literature. To complicate things further, the longwave/shortwave cancellation depends on some ambient parameters like ambient temperature, co-existing natural clouds, surface albedo and some others. Climate models are optimally suited to provide a representation of the required variety of ambient parameters for a climatological estimate of contrail radiative forcing. However, comprehensive global climate models have to use simplified radiative transfer schemes for reasons of computational economy. Hence, a dedicated test of these schemes is always indicated. We present a comparison of contrail radiative forcing between two contrail radiative forcing estimates from global climate models. The first is yielded with the ECHAM4 model frequently used for this purpose over the last ten years, the second by the more recent ECHAM5/EMAC model to be applied in the coming years. Use is made of the so-called "Myhre benchmark test" with specified contrail parameters. The ratio of longwave/shortwave cancellation for various seasons and the daytime/nighttime difference are features of particular focus. Contrail radiative forcing is difficult to determine even if the numerous key parameters like coverage, ice water content, crystal size etc. are known. One reason is the high degree of cancellation between the positive (warming) component from the contrails' greenhouse effect and the negative (cooling) component from backscattering of solar irradiance. This sets high demands on the abilities of the radiative transfer model, and a considerable uncertainty of respective calculations has been documented in literature. Furthermore, the longwave/shortwave cancellation is sensitive to several ambient parameters like temperature, co-existing natural clouds, and surface albedo.

Document Type:Conference or Workshop Item (Poster)
Title:Performance of two GCM borne radiation schemes in calculating contrail radiative forcing
Authors:
AuthorsInstitution or Email of Authors
Ponater, MichaelUNSPECIFIED
Frömming, ChristineUNSPECIFIED
Date:26 June 2012
Status:Published
Keywords:contrail, radiative forcing, longwave radiative flux, shortwave radiative flux
Event Title:3rd conference on Transport, Atmosphere, and Climate (TA3-3)
Event Location:Prien am Chiemsee, Germany
Event Type:international Conference
Event Dates:25-28 Jun 2012
Organizer:DLR
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
Institute of Atmospheric Physics > Atmospheric Dynamics
Deposited By: Dr.rer.nat. Michael Ponater
Deposited On:08 Oct 2012 16:19
Last Modified:08 Oct 2012 16:19

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