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SECTION 4. STANDARD ATMOSPHERE

1. Characteristics

Several general characteristics of the atmosphere have already been mentioned, but in order
to measure a change from normal, we have to establish a standard for a "normal"
atmosphere. Conditions through the world for all areas and all seasons have been averaged
to determine:

a. a surface temperature of 59°F (15°C) at sea level
b. a surface pressure of 29.92 inches of mercury (1013.2 millibars) or 14.7 pounds
per square inch at sea level
c. a lapse rate (decrease of temperature with height) in the troposphere of
approximately 2°C per thousand feet

d. a tropopause of approximately 36,000 feet
e. a temperature at the tropopause of -55°c