Thermal expansion of atmosphere and stability of vertically stratified fluids

The influence of 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-Väisälä frequency is derived, and a critical value of the thermal expansion coefficient for which the instability occurs is revealed. •The stability of atmospheric stratified fluids is studied.•The thermal expansion leads to the instability of incompressible flows.•The Brunt-Väisälä frequency is modified by the effects of the thermal expansion.•A critical value of the thermal expansion coefficient is revealed.