Journal cover Journal topic
Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
Geosci. Model Dev., 10, 3207-3223, 2017
https://doi.org/10.5194/gmd-10-3207-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Development and technical paper
01 Sep 2017
Practice and philosophy of climate model tuning across six US modeling centers
Gavin A. Schmidt1, David Bader2, Leo J. Donner3, Gregory S. Elsaesser1,4, Jean-Christophe Golaz2, Cecile Hannay5, Andrea Molod6, Richard B. Neale5, and Suranjana Saha7 1NASA Goddard Institute for Space Studies, 2880 Broadway, New York, USA
2DOE Lawrence Livermore National Laboratory, Livermore, California, USA
3GFDL/NOAA, Princeton University Forrestal Campus, 201 Forrestal Rd., Princeton, New Jersey, USA
4Columbia University, New York, New York, USA
5National Center for Atmospheric Research (NCAR), Boulder, Colorado, USA
6Global Modeling and Assimilation Office, NASA GSFC, Greenbelt, Maryland, USA
7Environmental Modeling Center, NCEP/NWS/NOAA, NCWCP College Park, Maryland, USA
Abstract. Model calibration (or tuning) is a necessary part of developing and testing coupled ocean–atmosphere climate models regardless of their main scientific purpose. There is an increasing recognition that this process needs to become more transparent for both users of climate model output and other developers. Knowing how and why climate models are tuned and which targets are used is essential to avoiding possible misattributions of skillful predictions to data accommodation and vice versa. This paper describes the approach and practice of model tuning for the six major US climate modeling centers. While details differ among groups in terms of scientific missions, tuning targets, and tunable parameters, there is a core commonality of approaches. However, practices differ significantly on some key aspects, in particular, in the use of initialized forecast analyses as a tool, the explicit use of the historical transient record, and the use of the present-day radiative imbalance vs. the implied balance in the preindustrial era as a target.

Citation: Schmidt, G. A., Bader, D., Donner, L. J., Elsaesser, G. S., Golaz, J.-C., Hannay, C., Molod, A., Neale, R. B., and Saha, S.: Practice and philosophy of climate model tuning across six US modeling centers, Geosci. Model Dev., 10, 3207-3223, https://doi.org/10.5194/gmd-10-3207-2017, 2017.
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Short summary
The development of coupled ocean atmosphere climate models is a complex process that inevitably includes multiple calibration steps (sometimes called tuning). Tuning uses degrees of freedom allowed by uncertainties in model approximations to modify parameters to make the simulation better align with some selected observed target(s). We describe how these tuning targets, parameters, and philosophy vary across six US modeling centers in order to increase the transparency of the practice.
The development of coupled ocean atmosphere climate models is a complex process that inevitably...
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