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  • Author or Editor: David P. Baumhefner x
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Warren M. Washington
and
David P. Baumhefner

Abstract

A simple method of reducing the amplitude of Lamb waves in primitive equation model forecasts has been proposed and tested. This method makes use of a Boussinesq-type approximation in which the vertical mean mass divergence is set equal to zero. It effectively reduces the Lamb waves by a factor of 3 in the example shown here and does not degrade the forecast accuracy. The largest reduction in Lamb wave amplitude is found in the tropical regions.

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David D. Houghton
,
David P. Baumhefner
, and
Warren M. Washington

Abstract

The problem of obtaining initial values for vertical motion and the divergent component of horizontal velocity is examined for a global primitive equation model. Only diagnostic methods are considered, the emphasis being on uniform application over the globe rather than a high degree of accuracy. Results show that a very simple diagnostic equation similar in form to the omega equation provides for realistic values of vertical motion in high and middle latitudes and smooth variations across tropical latitudes. In terms of prediction accuracy, no improvement is noted by using the computed initial vertical motions instead of zero for the initial vertical motions in a six-layer, 5° mesh model. In both cases unrealistic oscillations occur during the first 12 hr.

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