A Scheme of Dynamic Initialization of the Boundary Layer in a Primitive Equation Model

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  • 1 Geophysical Fluid Dynamics Laboratory/NOAA, Princeton University, Princeton, N.J. 08540
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Abstract

A scheme of dynamic initialization of a primitive equation model is proposed with an emphasis on the dynamic adjustment in the boundary layer. The pre-initialintion analysis is important since the restorative method is used in the subsequent dynamic initialization. The first phase of dynamic initialization is designed to establish a reasonable boundary layer structure. For this purpose, a time integration of the primitive equations is performed under a strong constraint such that all meteorological fields except momentum in the boundary layer are frozen. Use of an implicit form for the vertical diffusion term is recommended. The second phase is formulated to reduce the high-frequency noise in the final initialized field. Cyclic integration with a selective damping scheme is carried out under a restorative constraint.

The proposed scheme is applied to a case of simple zonal flow and the evolution of the boundary layer flow is shown. The scheme is also tested for a cam of mature tropical cyclone. Starting from the wind data in the free atmosphere only, the initial condition of the model is derived. Subsequent time integration of the model compares favorably with the integration in a control experiment.

Abstract

A scheme of dynamic initialization of a primitive equation model is proposed with an emphasis on the dynamic adjustment in the boundary layer. The pre-initialintion analysis is important since the restorative method is used in the subsequent dynamic initialization. The first phase of dynamic initialization is designed to establish a reasonable boundary layer structure. For this purpose, a time integration of the primitive equations is performed under a strong constraint such that all meteorological fields except momentum in the boundary layer are frozen. Use of an implicit form for the vertical diffusion term is recommended. The second phase is formulated to reduce the high-frequency noise in the final initialized field. Cyclic integration with a selective damping scheme is carried out under a restorative constraint.

The proposed scheme is applied to a case of simple zonal flow and the evolution of the boundary layer flow is shown. The scheme is also tested for a cam of mature tropical cyclone. Starting from the wind data in the free atmosphere only, the initial condition of the model is derived. Subsequent time integration of the model compares favorably with the integration in a control experiment.

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