Geosci. Model Dev. Discuss., 4, 641-688, 2011
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This discussion paper has been under review for the journal Geoscientific Model Development (GMD). Please refer to the corresponding final paper in GMD.
The Joint UK Land Environment Simulator (JULES), Model description – Part 2: Carbon fluxes and vegetation
D. B. Clark1, L. M. Mercado1, S. Sitch2, C. D. Jones3, N. Gedney4, M. J. Best3, M. Pryor4, G. G. Rooney3, R. L. H. Essery5, E. Blyth1, O. Boucher3, R. J. Harding1, and P. M. Cox6
1Centre for Ecology and Hydrology, Wallingford, OX10 8BB, UK
2School of Geography, University of Leeds, Leeds LS2 9JT, UK
3Met Office Hadley Centre, Exeter, EX1 3PB, UK
4Met Office, Joint Centre for Hydro-Meteorological research, Wallingford, OX10 8BB, UK
5School of GeoSciences, University of Edinburgh, EH9 3JW, Edinburgh, UK
6College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, EX4 4QF, UK

Abstract. The Joint UK Land Environment Simulator (JULES) is a process-based model that simulates the fluxes of carbon, water, energy and momentum between the land surface and the atmosphere. Past studies with JULES have demonstrated the important role of the land surface in the Earth System. Different versions of JULES have been employed to quantify the effects on the land carbon sink of separately changing atmospheric aerosols and tropospheric ozone, and the response of methane emissions from wetlands to climate change. There was a need to consolidate these and other advances into a single model code so as to be able to study interactions in a consistent manner. This paper describes the consolidation of these advances into the modelling of carbon fluxes and stores, in the vegetation and soil, in version 2.2 of JULES. Features include a multi-layer canopy scheme for light interception, including a sunfleck penetration scheme, a coupled scheme of leaf photosynthesis and stomatal conductance, representation of the effects of ozone on leaf physiology, and a description of methane emissions from wetlands. JULES represents the carbon allocation, growth and population dynamics of five plant functional types. The turnover of carbon from living plant tissues is fed into a 4-pool soil carbon model. The process-based descriptions of key ecological processes and trace gas fluxes in JULES mean that this community model is well-suited for use in carbon cycle, climate change and impacts studies, either in standalone mode or as the land component of a coupled Earth system model.

Citation: Clark, D. B., Mercado, L. M., Sitch, S., Jones, C. D., Gedney, N., Best, M. J., Pryor, M., Rooney, G. G., Essery, R. L. H., Blyth, E., Boucher, O., Harding, R. J., and Cox, P. M.: The Joint UK Land Environment Simulator (JULES), Model description – Part 2: Carbon fluxes and vegetation, Geosci. Model Dev. Discuss., 4, 641-688, doi:10.5194/gmdd-4-641-2011, 2011.
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