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Atmos. Chem. Phys. Discuss., 9, 22865-22881, 2009
www.atmos-chem-phys-discuss.net/9/22865/2009/ doi:10.5194/acpd-9-22865-2009 © Author(s) 2009. This work is distributed under the Creative Commons Attribution 3.0 License. |
Effects of resolution on the relative importance of numerical and physical diffusion in atmospheric composition modelling
CNR-ISAC, via Gobetti 101, 40129 Bologna, Italy
Abstract. Numerical diffusion induced by advection has a large influence on concentration of substances in atmospheric composition models. At coarse resolutions numerical effects dominate, whereas at increasing model resolutions a description of physical diffusion is needed. The effects of changing resolution and Courant number are investigated for the WAF advection scheme (used in BOLCHEM), evidencing a sub-diffusive process. The spreading rate from an instantaneous source is compared with the physical diffusion necessary to simulate unresolved turbulent motions. The time at which the physical diffusion process overpowers the numerical spreading is estimated, and is shown to reduce as the resolution increases, and to increase with wind velocity.
Citation: D'Isidoro, M., Maurizi, A., and Tampieri, F.: Effects of resolution on the relative importance of numerical and physical diffusion in atmospheric composition modelling, Atmos. Chem. Phys. Discuss., 9, 22865-22881, doi:10.5194/acpd-9-22865-2009, 2009.