Thermal expansion of atmosphere and stability of vertically stratified fluids

The influence of the thermal expansion of the Earth’s atmosphere on the stability of vertical stratification of fluid density and temperature is studied. We show that such an influence leads to the instability of incompressible flows. Modified by the thermal expansion coefficient, a new expression for the Brunt-V{ä}is{ä}l{ä} frequency is derived, and a critical value of the thermal expansion coefficient for which the instability occurs is revealed.