Southern Hemisphere Forecast Experiments with a One-Level Spectral Model

Bryant J. McAvaney Australian Numerical Meteorology Research Centre, Melbourne, Victoria, 3001

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William Bourke Australian Numerical Meteorology Research Centre, Melbourne, Victoria, 3001

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Abstract

A one-level primitive equation spectral model has been initialized with hemispheric 500 mb geopotential height and vorticity fields using the Southern Hemisphere GARP data sets for the period 3–12 November 1969 inclusive. Experiments performed to choose values of the external parameters of the model showed that resolution up to wavenumber 15 and a mean free surface height of 5.6 km were suitable for 48 h prognoses. The distributions with respect to both latitude and planetary wavenumber in the mean square error were determined for the model prognoses. Over the mid-latitude range 30°S to 60°S and over the wavenumber range 3 to 9, 48 h prognoses proved consistently better than persistence.

Abstract

A one-level primitive equation spectral model has been initialized with hemispheric 500 mb geopotential height and vorticity fields using the Southern Hemisphere GARP data sets for the period 3–12 November 1969 inclusive. Experiments performed to choose values of the external parameters of the model showed that resolution up to wavenumber 15 and a mean free surface height of 5.6 km were suitable for 48 h prognoses. The distributions with respect to both latitude and planetary wavenumber in the mean square error were determined for the model prognoses. Over the mid-latitude range 30°S to 60°S and over the wavenumber range 3 to 9, 48 h prognoses proved consistently better than persistence.

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