Reflection of Planetary Waves in Three-Dimensional Tropospheric Flows

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Abstract
The authors consider quasi-stationary planetary waves that are excited by localized midlatitude orographic forcing in a three-dimensional primitive-equation model. The waves propagate toward subtropical regions where the background flow is weak and the waves are therefore likely to break. Potential vorticity fields on isentropic surfaces are used to diagnose wave breaking. Nonlinear pseudomomentum conservation relations are used to quantify the absorption–reflection behavior of the wave-breaking regions. Three different three-dimensional flow configurations are represented: (i) a barotropic flow, (ii) a simple baroclinic flow, and (iii) a more realistic baroclinic flow. In order to allow the propagation of large-scale waves to be studied over extended periods for the baroclinic flows, the authors apply a mechanical damping at low levels to delay the onset of baroclinic instability. For basic states (i) and (ii) the forcing excites a localized wave train that propagates into the subtropics and, fo... Abstract The authors consider quasi-stationary planetary waves that are excited by localized midlatitude orographic forcing in a three-dimensional primitive-equation model. The waves propagate toward subtropical regions where the background flow is weak and the waves are therefore likely to break. Potential vorticity fields on isentropic surfaces are used to diagnose wave breaking. Nonlinear pseudomomentum conservation relations are used to quantify the absorption–reflection behavior of the wave-breaking regions. Three different three-dimensional flow configurations are represented: (i) a barotropic flow, (ii) a simple baroclinic flow, and (iii) a more realistic baroclinic flow. In order to allow the propagation of large-scale waves to be studied over extended periods for the baroclinic flows, the authors apply a mechanical damping at low levels to delay the onset of baroclinic instability. For basic states (i) and (ii) the forcing excites a localized wave train that propagates into the subtropics and, fo...

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