Vertical Structure of the Atmosphere A. Pressure Changes Atmospheric Pressure: weight of the air above - at sea level, the avg. pressure ~ 1000 millibars (mb), or ~ 1 kg/cm2 Pressure at higher altitudes is less ? of the atmosphere is below 5.6 km (3.5 mi); at 16 km (10 mi), 90% of the atmosphere has been passed, and > 100 km (62 mi), only 0.00003 % of all gases in the atmosphere remain. Rest of atmosphere merges with space vacuum. B. Temperature Changes Near Earth?s surface, air temperature drops with an increase of height. I. Troposphere (air ?turns over?) Lowermost atmosphere layer (we live in here); temperature decreases with an altitude increase. All important weather occurs here.