A Comparison of Vertical Mode and Normal Mode Initialization

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  • 1 Division of Atmospheric Research Mordialloc, Victoria, Australia
  • | 2 Bureau of meteorology Research Centre, Melbourne, Victoria Australia
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Abstract

Vertical mode initialization (VMI) in a limited-area model is compared with normal mode initialization (NMI) as performed in a spectral model. Upon interpolating all datasets from the hemispheric spectral system, the greatest reduction of spurious oscillations in the limited-area system is found when its own VMI initialization scheme is used. The essential similarity of VMI and NMI is demonstrated by the close similarity of the vertical velocities and MSL pressure tendencies as derived in the respective systems. Reasonable agreement is found between regions of upward vertical velocity and cloudiness in the satellite imagery. The instantaneous mean-sea-level (MSL) pressure tendencies show qualitative agreement with time-averaged analysis tendencies over ocean areas, but disagree with tendencies over the land, seemingly as a result of diurnal heating effects.

Abstract

Vertical mode initialization (VMI) in a limited-area model is compared with normal mode initialization (NMI) as performed in a spectral model. Upon interpolating all datasets from the hemispheric spectral system, the greatest reduction of spurious oscillations in the limited-area system is found when its own VMI initialization scheme is used. The essential similarity of VMI and NMI is demonstrated by the close similarity of the vertical velocities and MSL pressure tendencies as derived in the respective systems. Reasonable agreement is found between regions of upward vertical velocity and cloudiness in the satellite imagery. The instantaneous mean-sea-level (MSL) pressure tendencies show qualitative agreement with time-averaged analysis tendencies over ocean areas, but disagree with tendencies over the land, seemingly as a result of diurnal heating effects.

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