- Structure of the Atmosphere is covered in Topic 62.
Pressure is greatest close to the surface and decreases rather steadily with increasing altitude:
At the Tropopause, at an altitude of about 12 km, the pressure is about 30% of its surface value.
At an altitude of about 18 km (within the lower Stratosphere), the pressure is about 10% of its surface value.
At an altitude of about 32 km, the pressure is about 1/100 (1%) of its surface value.
At an altitude of about 48 km, the pressure is about 1/1000 (0.1%) of its surface value.
Temperature variation is complex:
- Troposphere temperature decreases with altitude, from an average of 20o C near the surface to about -60o C at the Tropopause.
- Stratosphere temperature is rather constant (near -60o C) in the lower Stratosphere (at altitudes from 12 to 20 km), then increases to near 0o C at the Stratopause.
- Mesosphere temperature decreases with altitude, from about 0o C just above the Stratopause to about -100o C at its upper limit (the Mesopause).
- Thermosphere temperature increases with altitude, gradually in the lower Thermosphere (from an altitude of 85 km to around 100 km), then rapidly
to about 300o C at an altitude of 120 km,
then more gradually to about 500o C at an altitude of about 600 km.
Other variation:
- The height of the Tropopause actually varies with latitude (higher above the Equator, lower above the poles) and seasonally (higher in summer, lower in winter).
- The Thermospher's maximum temperature varies from about 500 to 2,000 degrees Celsius, hotter by day than at night.
- The height of the Thermopause fluctuates quite a lot.
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