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Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/gmd-2018-90
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Model description paper
24 Apr 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Geoscientific Model Development (GMD).
Climate model configurations of the ECMWF Integrated Forecast System (ECMWF-IFS cycle 43r1) for HighResMIP
Christopher D. Roberts1,2, Retish Senan1, Franco Molteni1, Souhail Boussetta1, Michael Mayer1, and Sarah Keeley1 1European Centre for Medium-Range Weather Forecasts, Shinfield Park, Reading, RG2 9AX, United Kingdom
2Met Office, Fitzroy Road, Exeter, EX1 3PB, United Kingdom
Abstract. This paper presents atmosphere-only and coupled climate model configurations of the European Centre for Medium-Range Weather Forecasts Integrated Forecast System (ECMWF-IFS) for different combinations of ocean and atmosphere resolution. These configurations are used to perform multi-decadal ensemble experiments following the protocols of the High Resolution Model Intercomparison Project (HighResMip) and phase 6 of the Coupled Model Intercomparison Project (CMIP6). These experiments are used to evaluate the sensitivity of major biases in the atmosphere, ocean, and cryosphere to changes in atmosphere and ocean resolution. Climatological surface biases in ECMWF-IFS are relatively insensitive to an increase in atmospheric resolution from ~50 km to ~25 km. However, increasing the horizontal resolution of the atmosphere while maintaining the same vertical resolution enhances the magnitude of a cold bias in the lower stratosphere. In coupled configurations, there is a strong sensitivity to an increase in ocean model resolution from 1° to 0.25°. However, this sensitivity to ocean resolution takes many years to fully manifest and is not apparent in the first year of integration. This result has implications for the ECMWF coupled model development strategy that typically relies on the analysis of biases in short (< 1 year) ensemble (re)forecast data sets. The impacts of increased ocean resolution are particularly evident in the North Atlantic and Arctic, where they are associated with an improved Atlantic meridional overturning circulation, increased meridional ocean heat transports, and more realistic sea-ice cover. In the tropical Pacific, increased ocean resolution is associated with improvements to the magnitude and asymmetry of ENSO variability and better representation of non-linear SST-radiation feedbacks during warm events. However, increased ocean model resolution also increases the magnitude of a warm bias in the Southern Ocean. Finally, there is tentative evidence that both ocean coupling and increased atmospheric resolution can improve teleconnections between tropical Pacific rainfall and geopotential height anomalies in the North Atlantic.
Citation: Roberts, C. D., Senan, R., Molteni, F., Boussetta, S., Mayer, M., and Keeley, S.: Climate model configurations of the ECMWF Integrated Forecast System (ECMWF-IFS cycle 43r1) for HighResMIP, Geosci. Model Dev. Discuss., https://doi.org/10.5194/gmd-2018-90, in review, 2018.
Christopher D. Roberts et al.
Christopher D. Roberts et al.
Christopher D. Roberts et al.

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This paper presents climate model configurations of the European Centre for Medium-Range Weather Forecasts Integrated Forecast System (ECMWF-IFS) for different combinations of ocean and atmosphere resolution. These configurations are used to perform multi-decadal experiments following the protocols of the High Resolution Model Intercomparison Project (HighResMip) and phase 6 of the Coupled Model Intercomparison Project (CMIP6).
This paper presents climate model configurations of the European Centre for Medium-Range Weather...
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