In this month's enRoute's September 2016 edition, I wrote about the tropopause. Much of it was kept in tack except about thunderstorm heights. That's deemed "uncomfortable knowledge" for the passenger in 22B. Funny, preflight announcements discuss evacuations, jumping out of an airplane with a lifevest on, rapid depressurization and tell them to keep buckled in because of unexpected turbulence. :)
Here are some facts I mustered up about the tropopause. It's a given a C-172 driver hasn't a care about the "trop" but they may grow up to be a "tropopause penetrators." :)
Tropopause: Boundary between the first two layers of the atmosphere.
The tropopause, the interface separating the troposphere (the layer in which we live) and the stratosphere, is significant regarding weather and airline operations. This transition level: defines the top of our weather (including most thunderstorm heights), where winds are strongest, where possible bumps may occur, where jet streams lurk, and where temperature becomes isothermal or rises. But it’s also coincidental to where jet engines are most efficient. On every flight plan, the tropopause height is depicted along a pilot’s route as its whereabouts fluctuates depending on latitude, season and weather patterns.
Fact. The standard height of the tropopause is 36,089 feet (11,000 metres) within the height jet engines are most efficient.
Fact. The tropopause is higher in the summer, lowest near the poles and highest near the equator.
Fact. The tropopause forms a lid as to how high a thunderstorm will grow (usually). A tropopause height of 45,000 feet means a thunderstorm has the potential of billowing to this level.
Fact. Jet streams (fast meandering currents of air) are co-located within the tropopause.
Fact. The word tropopause is abbreviated as “trop” in the aviation world, but is spoken as “trope” (it rhymes with rope).
Fact. Upper air balloons launched twice a day from over 900 stations around the world determine the whereabouts of the tropopause.
Fact. The flattening effect at the top of a thunderstorm, called an anvil (think blacksmith’s anvil), is caused by the tropopause acting as a lid due to temperature changes.
Fact. Tropopause height varies from 25,000’ at the poles to more than double that height to near 55,000’ at the equator.
Fact. Pilots input the tropopause height into the flight management computer to fine tune predictions.
Fact. Whenever bumps start at cruising altitude, I immediately check to see if I am near the tropopause. Sometimes a simple change in altitude is all that is required to make it smooth.
36,089: Average tropopause height in feet (feet is used in aviation), which is a direct conversion of 11,000 meters.
2: The average rate temperature decreases with height in Celsius per 1000 feet until it reaches the tropopause.
-56.5: Average temperature in Celsius at the tropopause
4: Number of atmosphere layers: troposphere, stratosphere, mesosphere and thermosphere.