Two‐dimensional linear lee wave modes for models including a stratosphere

Lee waves in the lower stratosphere are estimated by a consideration of natural wave ‘modes’ which have complex wavenumber and hence decay with distance in the downstream direction. For simple two layer troposphere‐stratosphere models the ‘leaky modes’ can be evaluated explicitly and compared with computed waves. When there is a layer of neutral stability in the upper troposphere the natural complex wave‐numbers are responsible for some quasi‐resonance phenomena.