An atmosphere defined as follows: a) the air is a perfect dry gas; b) the physical constants are: - Sea level mean molar mass: M0 = 28.964 420 � 10-3 kg mol-1 -Sea level atmospheric pressure: P0 = 1 013.250 hPa - Sea level temperature: t0 = 15�C T0 = 288.15 K - Sea level atmospheric density: ?0 = 1.225 0 kg m-3 - Temperature of the ice point: Ti = 273.15 K - Universal gas constant: R* = 8.314 32 JK-1mol-1 c) the temperature gradients are: Geopotential altitude (km) Temperature gradient (Kelvin per standard From To geopotential kilometre) -5.0 11.0 -6.5 11.0 20.0 0.0 20.0 32.0 +1.0 32.0 47.0 +2.8 47.0 51.0 0.0 51.0 71.0 -2.8 71.0 80.0 -2.0