Contact: Keith Williams

Transpose-AMIP is a WMO Working Group on Numerical Experiments (WGNE) and Working Group on Coupled Models (WGCM) endorsed activity to run climate models in weather-forecasts mode. Running weather forecasts (or more correctly hindcasts, as they are run retrospectively) with climate models enables detailed evaluation of the processes operating through a comparison of the model with a variety of observations for particular meteorological events. In addition understanding the development of biases as they grow from a well initialised state can provide significant insight into the cause of those biases, which can be used in the future development of the model. Many of the principal sources of model spread in terms of simulating climate and climate change are 'fast-processes' (e.g. clouds), hence examining and intercomparing climate models on these fast timescales could yield greater understanding of why their longer timescale response differs.

The transpose-AMIP project began with a pilot project (the CCPP-ARM Parameterization Testbed (CAPT)) which trialled the approach in the USA using the NCAR model (Phillips et al., 2004). The transpose-AMIP phase I experiment followed and was performed by 6 modelling centres with analysis focussed on the Southern Great Plains ARM site. Now that the concept has been proven and benefits already being realised as indicated by the list of references which follow, the intention for phase II of the project is to expand the data collection to be global with more diagnostics being saved, more modelling groups to taking part, and for more analysis of the data to take place.


  • Phillips, T.J., G.L. Potter, D.L. Williamson, R.T. Cederwall, J.S. Boyle, M. Fiorino, J.J. Hnilo, J.G. Olson, S. Xie, and J.J. Yio, 2004: Evaluating Parameterizations in General Circulation Models: Climate Simulation Meets Weather Prediction. Bull. Amer. Meteor. Soc., 85, 1903–1915.
  • Williams K.D., A. Bodas-Salcedo, M. Deque, S. Fermepin, B. Medeiros, M. Watanabe, C. Jakob, S.A. Klein, C.A. Senior and D.L. Williamson (2013) The Transpose-AMIP II experiment and its application to the understanding of Southern Ocean cloud biases in climate models. J. Climate. 26 3258-3274 doi:10.1175/JCLI-D-12-00429.1