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Kevin Walsh
and
John L. McGregor

Abstract

High-resolution climate simulations are presented for January and July over the Australian region using a limited-area model nested within a GCM. One new aspect of these simulations is that the model domain extends to tropical regions both north and south of the equator. Objective measures of skill are used to assess the quality of the model simulations, and the performance of the model is verified over various subregions of the model domain. Poleward of tropical regions, the nested model climatologies produced are generally superior to those produced by the GCM, and compare reasonably well to observations over the Australian continent at the regional scale; in particular the simulations of precipitation and screen temperature are improved.

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Terry L. Hart
,
William Bourke
,
Bryant J. McAvaney
,
Bruce W. Forgan
, and
John L. McGregor

Abstract

Results are presented for perpetual January and July general circulation simulations using the Australian Bureau of Meteorology Research Centre global spectral model. Particular emphasis is placed on the impact of changes in the physical parameterizations and horizontal resolution on the modeled fields. The results include variances and eddy transports as well as zonal means and geographical distributions. Of the experiments conducted the most satisfactory results were obtained using stability-dependent vertical diffusion and a combination of the Kuo scheme for deep convection and the Tiedtke shallow convection scheme.

The simulation of the polar night region of the stratosphere in January was much more realistic than in results obtained using an earlier version of the model. The improvement is attributed to the revised radiation code, supporting the conclusions of Ramanathan et al. on the sensitivity of simulations of this region of the atmosphere to the treatment of radiative processes.

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