Reassessing properties and radiative forcing of contrail cirrus using a climate model. Issue 16 (27th August 2016)

• Record Type: Journal Article
• Authors: Bock, Lisa; Burkhardt, Ulrike
• Is Part Of: Journal of geophysical research. Volume 121:Issue 16(2016)
• Page Start: 9717
• Page End: 9736
• Publication Date: 2016-08-27
• Subjects: contrail cirrus -- contrails in climate model -- radiative forcing of contrails; Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1002/2016JD025112
• Languages: English
• ISSNs: 2169-897X

Abstract

Abstract: Contrail cirrus is the largest known component contributing to the radiative forcing associated with aviation. Despite major advances simulating contrail cirrus, their microphysical and optical properties and the associated radiative forcing remain largely uncertain. We use a contrail cirrus parameterization in a global climate model which was extended to include a microphysical two‐moment scheme. This allows a more realistic representation of microphysical processes, such as deposition and sedimentation, and therefore of the microphysical and optical properties of contrail cirrus. The simulated contrail microphysical and optical properties agree well with in situ and satellite observations. As compared to estimates using an older version of the contrail cirrus scheme, the optical depth of contrail cirrus is significantly higher, particularly in regions with high air traffic density, due to high ice crystal number concentrations on the main flight routes. Nevertheless, the estimated radiative forcing for the year 2002 supports our earlier results. The global radiative forcing of contrail cirrus for the year 2006 is estimated to be 56mW/m 2 . A large uncertainty of the radiative forcing estimate appears to be connected with the, on average, very small ice crystal radii simulated in the main air traffic areas, which make the application of a radiative transfer parameterization based on geometric optics questionable. Key Points: Contrail cirrus properties and radiative forcing using a microphysical two‐moment scheme Contrail cirrus optical depth is significantly higher than in earlier simulations in line with observations Despite increase in contrail cirrus optical depth simulations confirm earlier radiative forcing estimates