Articles | Volume 10, issue 10
Geosci. Model Dev., 10, 3715–3743, 2017
Geosci. Model Dev., 10, 3715–3743, 2017

Model description paper 12 Oct 2017

Model description paper | 12 Oct 2017

The BRIDGE HadCM3 family of climate models: HadCM3@Bristol v1.0

Paul J. Valdes1, Edward Armstrong1, Marcus P. S. Badger1,2, Catherine D. Bradshaw3, Fran Bragg1, Michel Crucifix4, Taraka Davies-Barnard1,5, Jonathan J. Day6, Alex Farnsworth1, Chris Gordon7, Peter O. Hopcroft1, Alan T. Kennedy1, Natalie S. Lord1, Dan J. Lunt1, Alice Marzocchi8, Louise M. Parry1,9, Vicky Pope11, William H. G. Roberts1, Emma J. Stone1, Gregory J. L. Tourte1, and Jonny H. T. Williams10 Paul J. Valdes et al.
  • 1School of Geographical Sciences, University of Bristol, Bristol, UK
  • 2School of Environment, Earth and Ecosystem Sciences, The Open University, Milton Keynes, UK
  • 3Applied Science group, Met Office Hadley Centre, Exeter, UK
  • 4Earth and Life Institute, Georges Lemaître Centre for Earth and Climate Research, Université catholique de Louvain, Louvain-la-Neuve, Belgium
  • 5College of Engineering, Mathematics, and Physical Sciences, University of Exeter, Laver Building, North Park Road Exeter, EX4 4QE, UK
  • 6Department of Meteorology, University of Reading, Reading, UK
  • 7Centre for Climate Research Singapore, Meteorological Service Singapore, Singapore
  • 8Department of the Geophysical Sciences, The University of Chicago, Chicago, IL, USA
  • 9Scottish Environment Protection Agency (SEPA), Perth, UK
  • 10National Institute of Water and Atmospheric Research (NIWA), Wellington, New Zealand
  • 11Met Office, Hadley Centre, Fitzroy Road, Exeter, UK

Abstract. Understanding natural and anthropogenic climate change processes involves using computational models that represent the main components of the Earth system: the atmosphere, ocean, sea ice, and land surface. These models have become increasingly computationally expensive as resolution is increased and more complex process representations are included. However, to gain robust insight into how climate may respond to a given forcing, and to meaningfully quantify the associated uncertainty, it is often required to use either or both ensemble approaches and very long integrations. For this reason, more computationally efficient models can be very valuable tools. Here we provide a comprehensive overview of the suite of climate models based around the HadCM3 coupled general circulation model. This model was developed at the UK Met Office and has been heavily used during the last 15 years for a range of future (and past) climate change studies, but has now been largely superseded for many scientific studies by more recently developed models. However, it continues to be extensively used by various institutions, including the BRIDGE (Bristol Research Initiative for the Dynamic Global Environment) research group at the University of Bristol, who have made modest adaptations to the base HadCM3 model over time. These adaptations mean that the original documentation is not entirely representative, and several other relatively undocumented configurations are in use. We therefore describe the key features of a number of configurations of the HadCM3 climate model family, which together make up HadCM3@Bristol version 1.0. In order to differentiate variants that have undergone development at BRIDGE, we have introduced the letter B into the model nomenclature. We include descriptions of the atmosphere-only model (HadAM3B), the coupled model with a low-resolution ocean (HadCM3BL), the high-resolution atmosphere-only model (HadAM3BH), and the regional model (HadRM3B). These also include three versions of the land surface scheme. By comparing with observational datasets, we show that these models produce a good representation of many aspects of the climate system, including the land and sea surface temperatures, precipitation, ocean circulation, and vegetation. This evaluation, combined with the relatively fast computational speed (up to 1000 times faster than some CMIP6 models), motivates continued development and scientific use of the HadCM3B family of coupled climate models, predominantly for quantifying uncertainty and for long multi-millennial-scale simulations.

Short summary
In this paper we describe the family of climate models used by the BRIDGE research group at the University of Bristol as well as by various other institutions. These models are based on the UK Met Office HadCM3 models and here we describe the various modifications which have been made as well as the key features of a number of configurations in use.