Abstract: Replacing the equation of the quasi-static isothermal process by the quasi-static polytropic process of the ideal gas, the barometric formula of polytropic process is deduced, which is better improvement on the barometric formula of isothermal process. The altitude dependences of the barometric pressure are given for the various five cases in which value of the polytropic index n is taken as 1.0, 1.1, 1.2, 1.3, 1.4, respectively. The improvement on the barometric formula is also discussed due to the gravitational acceleration is changed as the altitude is changed.

Key words: barometric formula of isothermal process, quasi-static polytropic process, polytropic index, barometric pressure, ideal gas