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A Comparison of Mass and Energy Budgets from Two FGGE Datasets and a GCM

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  • 1 Canadian Climate Centre, Downsview, Ontario, Canada
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Abstract

Vertically integrated budgets of mass and energy for the global atmosphere, based on the ECMWF and GFDL FGGE III-b datasets for July 1979, have been obtained and compared with one another and with the results of a general circulation model. The rotational component of the mass and energy fluxes are reasonably well-measured and differences between the two FGGE analyses are an order of magnitude smaller than the values of the quantities themselves.

This is not the case for the divergent component of the mass and energy fluxes where the difference between analyses is of the same order of magnitude as the fields themselves. Since it is the divergence of this component of the energy flux that gives the distribution of energy sources and sinks, this quantity also differs markedly between analyses.

The difference in the calculated divergent energy fluxes, and the sources and sinks is primarily due to the difference in the time–mean component of the energy flux. The transient component of the flux is in comparatively good agreement.

The energy fluxes and source/sink distribution simulated by the CCC GCM agree, at least qualitatively, with those of the observations for the rotational component of the energy flux. For the divergent component, the model results agree most closely with those of the ECMWF analysis, which are weaker than those of the GFDL analysis.

If the differences in energy fluxes and energy sources and sinks between these two FGGE analyses are indicative of the uncertainties in these quantities, it would appear that it is not yet possible to infer oceanic transports from the knowledge of atmospheric transports and the radiative balance at the top of the atmosphere.

Abstract

Vertically integrated budgets of mass and energy for the global atmosphere, based on the ECMWF and GFDL FGGE III-b datasets for July 1979, have been obtained and compared with one another and with the results of a general circulation model. The rotational component of the mass and energy fluxes are reasonably well-measured and differences between the two FGGE analyses are an order of magnitude smaller than the values of the quantities themselves.

This is not the case for the divergent component of the mass and energy fluxes where the difference between analyses is of the same order of magnitude as the fields themselves. Since it is the divergence of this component of the energy flux that gives the distribution of energy sources and sinks, this quantity also differs markedly between analyses.

The difference in the calculated divergent energy fluxes, and the sources and sinks is primarily due to the difference in the time–mean component of the energy flux. The transient component of the flux is in comparatively good agreement.

The energy fluxes and source/sink distribution simulated by the CCC GCM agree, at least qualitatively, with those of the observations for the rotational component of the energy flux. For the divergent component, the model results agree most closely with those of the ECMWF analysis, which are weaker than those of the GFDL analysis.

If the differences in energy fluxes and energy sources and sinks between these two FGGE analyses are indicative of the uncertainties in these quantities, it would appear that it is not yet possible to infer oceanic transports from the knowledge of atmospheric transports and the radiative balance at the top of the atmosphere.

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