The sensitivity of the main characteristics of baroclinically unstable waves with respect to fundamental parameters of the atmosphere (the static stability parameter and vertical shear of a zonal wind ) is theoretically explored. Two types of waves are considered: synoptic scale waves and planetary scale (ultralong) waves based on an Eady-type model and model with vertically averaged primitive equations. Sensitivity functions are obtained that estimate the impact of variations in and on the growth rate and other characteristics of unstable waves and demonstrate that waves belonging to the short-wave part of the spectrum of unstable waves are more sensitive to changes in the static stability parameter than waves belonging to the long-wave part of the spectrum. The obtained theoretical results show that the increase of the static stability and decrease of the meridional temperature gradient in midlatitude baroclinic zones in some areas of the southern hemisphere lead to a slowing of the growth rate of baroclinic unstable waves and an increasing wavelength of baroclinic unstable wave maximum growth rate, that is, a spectrum shift of unstable waves towards longer wavelengths. These might affect the favorable conditions for the development of baroclinic instability and, therefore, the intensity of cyclone generation activity. 1. Introduction Static stability and the meridional temperature gradient (MTG) are among the most important fundamental parameters characterizing the state of the atmosphere and, in particular, midlatitude large-scale eddy dynamics [1, 2]. Static stability and MTG play a significant role in the development of baroclinic instability which is the dominant mechanism for generating large-scale atmospheric eddies (cyclones) that form the storm tracks in midlatitudes. The physical nature of baroclinic instability is well understood and explained in the scientific literature, including text books on dynamic meteorology (e.g., [1–4]). Baroclinic instability can be viewed as sloping convection where growing perturbations draw upon the available potential energy which is proportional to a meridional temperature gradient. Since the publication of the pioneering theoretical works of Charney [5] and Eady [6], in which the fundamental baroclinic mechanism of the atmospheric large-scale instability was first described, many scientific papers have been published that examine the growth of initially infinitesimal perturbations in the atmosphere and ocean caused by baroclinic effects. Both linear theory for the onset of baroclinic instability and its
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