q One way to measure how
soon the air runs out in the atmosphere is to calculate the height of an atmosphere of constant density that exerts the
same pressure as our atmosphere at Earth’s surface.
qThis height, which is about 10 km, is called the scale height of the atmosphere.
qOver this vertical distance, air
pressure and density decrease by 37% of its surface values.
qIf pressure at the surface is 1
atmosphere, then it is 0.37 atmospheres at a height of 10 km, 0.14 (0.37x0.37) at 20 km, 0.05 (0.37x0.37x0.37) at 30 km, and
so on.
qMost (80%) of the mass of the
atmosphere is confined in the first 10 km from the surface.