The effects of sensible heat exchange on the dynamics of baroclinic waves

Abstract

A diabatic two-level model with variable static stability is investigated with respect to the dynamic stability and thermal structure of harmonic perturbations. The exchange of sensible heat is assumed to be proportional to the difference in temperature between the air and the underlying surface. This type of diabatic heating reduces the instability of short and medium waves and shifts the maximum instability to a shorter wave length than the corresponding adiabatic model; however, the instability of long waves is increased. Solution of the initial value problem for various initial phase differences between the stream function wave, thermal wave and static stability waves show the importance of these parameters with respect to the growth characteristics which are complex. Limiting angles for a 4000-km wave length show an 85° lag of the thermal wave behind the stream wave and the latter lagging the vertical velocity and static stability waves by about 90° and 110° degrees respectively; but no significant differences are found between the adiabatic and diabatic cases. For an 8000-km wave length, the thermal wave lags the stream wave by about 30° and the stream wave, in turn, lags the static stability and vertical velocity waves by 140° with adiabatic flow, while with heat exchange the corresponding figures are 25° and 105°.