Journal cover Journal topic
Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
Geosci. Model Dev., 7, 2435-2475, 2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.
Model description paper
22 Oct 2014
Simulation of tropospheric chemistry and aerosols with the climate model EC-Earth
T. P. C. van Noije1, P. Le Sager1, A. J. Segers2, P. F. J. van Velthoven1, M. C. Krol3,4, W. Hazeleger1,3, A. G. Williams5, and S. D. Chambers5 1Royal Netherlands Meteorological Institute, De Bilt, the Netherlands
2Netherlands Organisation for Applied Scientific Research (TNO), Utrecht, the Netherlands
3Wageningen University, Wageningen, the Netherlands
4Institute for Marine and Atmospheric Research Utrecht, Utrecht University, Utrecht, the Netherlands
5Institute for Environmental Research, Australian Nuclear Science and Technology Organisation, Lucas Heights, Australia
Abstract. We have integrated the atmospheric chemistry and transport model TM5 into the global climate model EC-Earth version 2.4. We present an overview of the TM5 model and the two-way data exchange between TM5 and the IFS model from the European Centre for Medium-Range Weather Forecasts (ECMWF), the atmospheric general circulation model of EC-Earth. In this paper we evaluate the simulation of tropospheric chemistry and aerosols in a one-way coupled configuration. We have carried out a decadal simulation for present-day conditions and calculated chemical budgets and climatologies of tracer concentrations and aerosol optical depth. For comparison we have also performed offline simulations driven by meteorological fields from ECMWF's ERA-Interim reanalysis and output from the EC-Earth model itself. Compared to the offline simulations, the online-coupled system produces more efficient vertical mixing in the troposphere, which reflects an improvement of the treatment of cumulus convection. The chemistry in the EC-Earth simulations is affected by the fact that the current version of EC-Earth produces a cold bias with too dry air in large parts of the troposphere. Compared to the ERA-Interim driven simulation, the oxidizing capacity in EC-Earth is lower in the tropics and higher in the extratropics. The atmospheric lifetime of methane in EC-Earth is 9.4 years, which is 7% longer than the lifetime obtained with ERA-Interim but remains well within the range reported in the literature. We further evaluate the model by comparing the simulated climatologies of surface radon-222 and carbon monoxide, tropospheric and surface ozone, and aerosol optical depth against observational data. The work presented in this study is the first step in the development of EC-Earth into an Earth system model with fully interactive atmospheric chemistry and aerosols.

Citation: van Noije, T. P. C., Le Sager, P., Segers, A. J., van Velthoven, P. F. J., Krol, M. C., Hazeleger, W., Williams, A. G., and Chambers, S. D.: Simulation of tropospheric chemistry and aerosols with the climate model EC-Earth, Geosci. Model Dev., 7, 2435-2475,, 2014.
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