Abstract

The role of the Rossby parameter β due to the meridional variation of the Coriolis parameter f is investigated for inertio-gravity waves in midlatitudes based on a linear Boussinesq model without the traditional approximation, namely including the role of the horizontal component of the Coriolis ... Show moreThe role of the Rossby parameter β due to the meridional variation of the Coriolis parameter f is investigated for inertio-gravity waves in midlatitudes based on a linear Boussinesq model without the traditional approximation, namely including the role of the horizontal component of the Coriolis vector of the Earth's rotation. Without the β-effect, it is well established that the non-traditional Coriolis effects give rise to an additional mode of inertio-gravity (IG) waves whose frequencies are slightly smaller than the local Coriolis frequency f unlike the traditional IG-mode whose frequencies are larger than f. The addition of the β-effect modifies the properties of the sub-inertial and super-inertial IG-modes. These modifications are examined by calculating the model normal modes for a given vertical profile of the buoyancy frequency N. Inclusion of the β-effect yields the external and internal Rossby modes in addition to the IG-modes. Presence of the external Rossby mode in this model is a new result, since it does not occur in the traditional version with β nor in the non-traditional version without β. The normal-mode properties, including wave frequencies and eigenfunctions, are presented for various values of N. The normal-mode analysis is complemented by the initial-value approach to study the evolution of waves generated by forcing. The results of numerical time-integrations of wave generation in the ocean forced by atmospheric disturbances and by the interaction of tidal flows with bottom topography are presented to reveal a notable role of β for the IG-waves. Application to atmospheric problems is proposed. Copyright © 2010 Royal Meteorological Society Show less