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(For this question use annex 050-052).
Considering the North Atlantic route from the Azores to Bermuda, the mean height of the tropical tropopause during summer is approximately..
  • A
    47000 ft.
  • B
    39000 ft.
  • C
    60000 ft.
  • D
    33000 ft.

TROPOPAUSE

It is the boundary between the troposphere and the stratosphere and it is where the temperature ceases to fall with an increase in height. The tropopause height varies with latitude and season - and it is controlled by the temperature of the air near the surface.

- The warmer the air, the higher the tropopause. The higher it is, the colder the temperature at the tropopause.
- The colder the air, the lower the tropopause. The lower it is, the warmer the temperature at the tropopause.

The tropopause occurs at approximately 20,000 feet over the poles and at approximately 60,000 feet above the equator. The temperature at the tropopause can be as high as -40°C over the poles and as low as -80°C over the Equator. The International Standard Atmosphere (ISA) assumes that the average height of the tropopause is 36,000 feet, with a temperature of -56.5°C.

Calculating the average tropopause height (ft):
Tropopause height (ft) = (16 x cos Lat) x 3 280

  • for winter questions = subtract 3 000 ft; if summer = add 3 000 ft to the above result.

Looking at the chart, we can see that the route from Azores to Bermuda lies at around 33ºN.
Tropopause height = (16 x cos 33º) x 3280 = 44 000 ft
=> During summer, we have to add 3000 ft = 44 000 + 3 000 = 47 000 ft

Note: the formula described in this explanation gives an approximate value.

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