Baroclinic instability of easterly jets with applications to the summer mesosphere

A two-dimensional numerical analysis of baroclinic instability waves in zonally and seasonally averaged wind fields in the summer mesosphere is presented. The analysis is based on the linearized quasi-geostrophic potential vorticity equation of Simmons and Moskins (1973). Solutions are obtained for the wave structure, wave growth rates, and wave periods on the basis of idealized and realistic data, and the results are compared with one-dimensional analyses. It is shown that the wavenumbers of peak growth with periods of 1.4-3 days were consistently lower for the two-dimensional analysis than for previous one-dimensional analyses. The possibility of detecting baroclinic instability in summer winds at 80-100 km by means of nadir-sounding satellite observations is discussed.