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On the scale of baroclinic instability in deep, compressible atmospheres
Author(s) -
Read P. L.
Publication year - 1988
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.49711448008
Subject(s) - baroclinity , instability , inviscid flow , hydrostatic equilibrium , compressibility , mechanics , physics , radius , boundary value problem , geology , adiabatic process , thermodynamics , computer security , quantum mechanics , computer science
A simple model of linearized, inviscid baroclinic instability in an adiabatic, hydrostatic, compressible atmosphere of arbitrary (though finite) depth, based on the well‐known Eady model, is used to investigate the variation of growth rates and favoured horizontal length scales as functions of δ, the ratio of the model depth D to the density scale height Hs. Both geometric height coordinates (with w = 0 horizontal boundary conditions) and log‐pressure (with ω = 0 boundary conditions) are considered. For δ > 3 and a given zonal velocity scale, growth rates are significantly reduced relative to comparable instabilities in an incompressible fluid (δ = 0), and may be suppressed altogether in a laterally‐bounded channel for large enough δ at a given value of static stability. Where instability does occur, the length scales favoured are longer than for an incompressible fluid, and are generally comparable to a deformation radius based on D (rather than H s). The relationship between these results and those obtained in comparable recent studies (which have found scales comparable to a deformation radius based on H s to be important) is examined. Some implications for the role of baroclinic instability in the atmospheres of the major planets are also discussed.