Journal cover Journal topic
Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
Geosci. Model Dev., 8, 2435-2445, 2015
http://www.geosci-model-dev.net/8/2435/2015/
doi:10.5194/gmd-8-2435-2015
© Author(s) 2015. This work is distributed
under the Creative Commons Attribution 3.0 License.
Development and technical paper
05 Aug 2015
Revision of the convective transport module CVTRANS 2.4 in the EMAC atmospheric chemistry–climate model
H. G. Ouwersloot1, A. Pozzer1, B. Steil1, H. Tost2, and J. Lelieveld1 1Atmospheric Chemistry Department, Max Planck Institute for Chemistry, Mainz, Germany
2Institute for Atmospheric Physics, University of Mainz, Mainz, Germany
Abstract. The convective transport module, CVTRANS, of the ECHAM/MESSy Atmospheric Chemistry (EMAC) model has been revised to better represent the physical flows and incorporate recent findings on the properties of the convective plumes. The modifications involve (i) applying intermediate time stepping based on a settable criterion, (ii) using an analytic expression to account for the intra-time-step mixing ratio evolution below cloud base, and (iii) implementing a novel expression for the mixing ratios of atmospheric compounds at the base of an updraft. Even when averaged over a year, the predicted mixing ratios of atmospheric compounds are affected considerably by the intermediate time stepping. For example, for an exponentially decaying atmospheric tracer with a lifetime of 1 day, the zonal averages can locally differ by more than a factor of 6 and the induced root mean square deviation from the original code is, weighted by the air mass, higher than 40 % of the average mixing ratio. The other modifications result in smaller differences. However, since they do not require additional computational time, their application is also recommended.

Citation: Ouwersloot, H. G., Pozzer, A., Steil, B., Tost, H., and Lelieveld, J.: Revision of the convective transport module CVTRANS 2.4 in the EMAC atmospheric chemistry–climate model, Geosci. Model Dev., 8, 2435-2445, doi:10.5194/gmd-8-2435-2015, 2015.
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