Real-case simulations of aerosol-cloud interactions in ship tracks over the Bay of Biscay
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Date
2014-10-24Type
- Working Paper
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Abstract
Ship tracks provide an ideal test bed for studying aerosol-cloud interactions (ACI) andfor evaluating their representation in parameterisations. Regional modelling can be ofparticular use for this task, as this approach provides sufficient resolution to resolve thestructure of the produced track including their meteorological environment whilst relying on the same formulations of parameterisations as many general circulation models. Inthis work we simulate a particular case of ship tracks embedded in an optically thinstratus cloud sheet which was observed by a polar orbiting satellite at 12:00 UTC on 26 January 2003 around the Bay of Biscay.The simulations which include moving ship emissions show that the model is indeed able to capture the structure of the track at a horizontal grid spacing of 2km and toqualitatively capture the observed cloud response in all simulations performed. At leasta doubling of the cloud optical thickness was simulated in all simulations together withan increase in cloud droplet number concentration (by about 50cm−3) and decrease ineffective radius (by about 5 μm). Furthermore the ship emissions lead to an increase in liquid water path in at least 25 % of the track regions.We are confident in the model’s ability to capture key processes of ship trackformation. However, it was found that realistic ship emissions lead to unrealistic aerosolperturbations near the source regions within the simulated tracks due to grid-scaledilution and homogeneity. Combining the regional-modelling approach with comprehensive field studiescould likely improve our understanding of the sensitivities and biases in ACIparameterisations, and could therefore help to constrain global ACI estimates, whichstrongly rely on these parameterisations Show more
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https://doi.org/10.3929/ethz-b-000095521Publication status
publishedExternal links
Journal / series
Atmospheric Chemistry and Physics DiscussionsVolume
Pages / Article No.
Publisher
CopernicusOrganisational unit
03690 - Lohmann, Ulrike / Lohmann, Ulrike
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Is previous version of: https://doi.org/10.3929/ethz-b-000099515
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