Nonlinear Normal Mode Initialization of a Limited-Area Model: Inclusion of All Beta Terms in the Linearized Model Equations

S. J. Bijlsma Royal Netherlands Meteorological Institute, 3730 AE De Bilt, The Netherlands

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Abstract

A nonlinear normal mode initialization method with all of the beta terms included in the linearized model equations is formulated for a limited-area model. It is the extension of an earlier method examining the sensitivity of nonlinear normal mode initialization to the inclusion of nonstationary Rossby modes. It is shown that the eigenmodes of the two methods for sufficiently large equivalent depths do coincide approximately. Results of the two methods are compared. They show the equivalence between the f-plane approach and the inclusion of all or some of the beta terms for midlatitude initialization.

Abstract

A nonlinear normal mode initialization method with all of the beta terms included in the linearized model equations is formulated for a limited-area model. It is the extension of an earlier method examining the sensitivity of nonlinear normal mode initialization to the inclusion of nonstationary Rossby modes. It is shown that the eigenmodes of the two methods for sufficiently large equivalent depths do coincide approximately. Results of the two methods are compared. They show the equivalence between the f-plane approach and the inclusion of all or some of the beta terms for midlatitude initialization.

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