Report 6:  Sensitivity of Dynamical Quantities to Horizontal Resolution in a Climate Simulation with the ECMWF Atmospheric General Circulation Model (Cycle 33)

Boyle, James S.
October 1992, 40 pp. 

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The ECMWF model (cycle 33) was integrated for a full seasonal cycle at the four horizontal resolutions T21, T42, T63 and T106. Within the limits imposed by the varying horizontal resolution, all other aspects of the model were identical for each integration. In this paper a comparison is made of the dynamical aspects of the simulations. Fields of zonally averaged zonal wind, eddy heat and momentum fluxes, global divergent wind and vorticity, and stationary wave patterns are presented and compared for each resolution.

The conclusions reached by this study are: (1) T21 is qualitatively different from the highter resolutions; (2) the highest resolution does not provide a simulation which is egregiously superior to T42 and there are aspects of the T21 simulation, especially in tropical convection, which are clearly better than those of the higher resolutions; (3) aside from differences in smaller scale boundary forcing at the higher resolutions, the T42, T63, and T106 simulations are nearly identical in the dynamical aspects of the circulation considered here; (5) increasing horizontal resolution alone will evidently not result in an overall superior simulation unless other aspects of the model are modified pari passu. (pdf file)

UCRL-MI-123395