Global Average Temperature Oscillations in Numerical Weather Forecasts

David L. Williamson National Center for Atmospheric Research, Boulder, CO 80307

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Ronald M. Errico National Center for Atmospheric Research, Boulder, CO 80307

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Roger Daley Canadian Climate Centre, Downsview, Ontario, Canada

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Abstract

We illustrate systematic oscillations of the global average temperature in forecasts produced by the NCAR Community Climate Model (CCM). These oscillations are not simple linear oscillations associated with normal modes calculated about a state of rest Rather they result from an interaction between zonal-average gravity modes and zonal-average Rossby modes. Their amplitudes are related to the difference between the initial conditions and the model's average climate.

Abstract

We illustrate systematic oscillations of the global average temperature in forecasts produced by the NCAR Community Climate Model (CCM). These oscillations are not simple linear oscillations associated with normal modes calculated about a state of rest Rather they result from an interaction between zonal-average gravity modes and zonal-average Rossby modes. Their amplitudes are related to the difference between the initial conditions and the model's average climate.

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