West, REL, Stier, P, Jones, A et al. (5 more authors) (2014) The importance of vertical velocity variability for estimates of the indirect aerosol effects. Atmospheric Chemistry and Physics, 14 (12). 6369 - 6393. ISSN 1680-7316
Abstract
The activation of aerosols to form cloud droplets is dependent upon vertical velocities whose local variability is not typically resolved at the GCM grid scale. Consequently, it is necessary to represent the subgrid-scale variability of vertical velocity in the calculation of cloud droplet number concentration. This study uses the UK Chemistry and Aerosols community model (UKCA) within the Hadley Centre Global Environmental Model (HadGEM3), coupled for the first time to an explicit aerosol activation parameterisation, and hence known as UKCA-Activate. We explore the range of uncertainty in estimates of the indirect aerosol effects attributable to the choice of parameterisation of the subgrid-scale variability of vertical velocity in HadGEM-UKCA. Results of simulations demonstrate that the use of a characteristic vertical velocity cannot replicate results derived with a distribution of vertical velocities, and is to be discouraged in GCMs. This study focuses on the effect of the variance (σw2) of a Gaussian pdf (probability density function) of vertical velocity. Fixed values of σw (spanning the range measured in situ by nine flight campaigns found in the literature) and a configuration in which σw depends on turbulent kinetic energy are tested. Results from the mid-range fixed σw and TKE-based configurations both compare well with observed vertical velocity distributions and cloud droplet number conce.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2014 Author(s). This is an open access article under the terms of the Creative Commons Attribution 3.0 License |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 12 Aug 2014 13:05 |
Last Modified: | 16 Jan 2018 12:56 |
Published Version: | http://dx.doi.org/10.5194/acp-14-6369-2014 |
Status: | Published |
Publisher: | European Geosciences Union |
Identification Number: | 10.5194/acp-14-6369-2014 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:80085 |