The core of UKESM1 is the coupled physical climate model HadGEM3 (Hewitt et al. 2010) which represents key physical and dynamical processes in; the atmosphere, ocean, land and sea-ice. HadGEM3 will also be used for seasonal and decadal climate prediction at MOHC and for physical climate modelling studies. In collaboration with a range of NERC and MOHC scientists, the UKESM core group is working to further develop and couple a number of component models into HadGEM3 that represent key biogeochemical, aerosol and cryosphere processes. Inclusion of these models will move HadGEM3 from a physical coupled climate model into the 1st UK Earth system model. These component models include;
- The UK Chemistry and Aerosol (UCKA) model for troposphere-stratosphere trace gas chemistry (Morgenstern et al. 2009, O’Connor et al. 2013), coupled to a two-moment aerosol scheme; GLOMAP-mode (Mann et al. 2010). In addition to the full stratosphere-troposphere scheme a simplified (computationally cheaper) version of UKCA has been developed employing pre-computed oxidants and a tropospheric sulphur cycle linked to the same GLOMAP aerosol scheme.
- The Model of Ecosystem Dynamics, nutrient Utilisation, Sequestration and Acidification (MEDUSA, Yool et al. 2010, 2012) representing ocean biogeochemistry, in particular the marine carbon cycle.
- Further development of the terrestrial carbon cycle and vegetation in the Joint UK Land Environment Simulator (JULES , Best et al. 2011, Clark et al 2011) targeting; (i) inclusion of nitrogen limitation on vegetation and soil carbon processes, (ii) improved treatment of wetlands, (iii) an increased number of plant functional types and (iv) improved representation of permafrost processes.
- The model GLIMMER/BISICLES (Rutt et al. 2009, Cornford et al. 2013) to represent ice sheets on Greenland and Antarctic.
Figure 1 provides a schematic of the UKESM1 component models and their coupling through the OASIS coupler (Valcke et al. 2013).
Two versions of UKESM1 are under development, differing only in their resolution. UKESM1-hr is the high-resolution version, employing N216 (~60km) in the atmosphere and 0.25° in the ocean. UKESM1-lr is a low resolution, computationally faster, version, with an atmospheric resolution of N96 (~140km) and an ocean resolution of 1°. Both models fully resolve the troposphere and stratosphere using 85 vertical levels and have 75 levels in the ocean. To the degree possible, we aim to maintain a common set of process parameterizations in both models. Where modifications are necessary for improved performance at a specific resolution, these changes will be documented and the impact on simulation performance and future projection responses analysed. To give users flexibility in the level of process complexity for a given set of experiments, we will provide and support 3-4 configurations within each of the 2 released model resolutions, ranging from: (a) Full Earth system complexity (including stratosphere-troposphere UKCA chemistry and GLOMAP aerosols, full (terrestrial and marine) carbon cycle and inclusion of Antarctic and Greenland Ice sheets). (b) Interactive carbon-cycle with reduced atmospheric chemistry complexity. (c) The core physical model HadGEM3, with interactive carbon cycle disabled and simplified chemistry linked to the GLOMAP aerosol scheme.
The 2 model versions (UKESM1-lr and -hr) are being developed on a time scale suitable for application to the WCRP 6th Coupled Model Intercomparison Project (CMIP6). We aim to have UKESM1-lr ready by late summer 2016, with UKESM1-hr available a few months later. As each model version becomes scientifically ready for use it will be released to UK researchers contributing to CMIP6, with a subsequent, more formal community release of both versions a few months later.
Best, M. J. and co-authors. The Joint UK Land Environment Simulator (JULES), Model description – Part 1: Energy and water fluxes, Geosci. Model Dev. Discuss., 4, 595-640, doi:10.5194/gmdd-4-595-2011, 2011.
Clark, D. B. and co-authors. 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.
Cornford, S.L. and co-authors. “Adaptive mesh, finite volume modeling of marine ice sheets.”, Journal of Computational Physics, 232(1), 529-549, 2013.
Hewitt, H. T. and co-authors.: Design and implementation of the infrastructure of HadGEM3: the next-generation Met Office climate modelling system, Geosci. Model Dev. Discuss., 3, 1861-1937, doi:10.5194/gmdd-3-1861-2010, 2010.
Mann, G. W. and co-authors.: Description and evaluation of GLOMAP-mode: a modal global aerosol microphysics model for the UKCA composition-climate model, Geosci. Model Dev. Discuss., 3, 651-734, doi:10.5194/gmdd-3-651-2010, 2010.
Morgenstern, O. and co-authors.: Evaluation of the new UKCA climate-composition model – Part 1: The stratosphere, Geosci. Model Dev., 2, 43-57, doi:10.5194/gmd-2-43-2009, 2009.
O’Connor, F. M. and co-authors. Evaluation of the new UKCA climate-composition model – Part 2: The Troposphere, Geosci. Model Dev. Discuss., 6, 1743-1857, doi:10.5194/gmdd-6-1743-2013, 2013.
Rutt, I., M. Hagdorn, N. Hulton, and A. Payne, 2009: The Glimmer community ice sheet model. J. Geophys. Res., 114, F02004, doi:10.1029/2008JF001015.
Valcke S., T.Craig and L.Coquart. OASIS/MCT User Guide: CERFACS TR/CMGC/13/17, May 2013. User documentation
Yool, A., Popova, E. E., and Anderson, T. R.: MEDUSA: a new intermediate complexity plankton ecosystem model for the global domain, Geosci. Model Dev. Discuss., 3, 1939-2019, doi:10.5194/gmdd-3-1939-2010, 2010.
Yool, A., Popova, E. E., and Anderson, T. R.: MEDUSA-2.0: an intermediate complexity biogeochemical model of the marine carbon cycle for climate change and ocean acidification studies, Geosci. Model Dev., 6, 1767-1811, doi:10.5194/gmd-6-1767-2013, 2013.