1Atmospheric Chemistry Department, Max Planck Institute for Chemistry, Mainz, Germany
2Institute for Atmospheric Physics, University of Mainz, Mainz, Germany
Received: 09 Mar 2015 – Published in Geosci. Model Dev. Discuss.: 08 Apr 2015
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.
Revised: 26 Jun 2015 – Accepted: 16 Jul 2015 – Published: 05 Aug 2015
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.