FAA Aircraft Dispatcher (ADX)MeteorologyHard
A dispatcher notes that the jet stream along the planned route is unusually strong and associated with a sharp temperature gradient at the tropopause. What hazard is most closely associated with this feature?
- AConvective thunderstorm activity
- BFreezing drizzle
- CClear air turbulence (CAT)
- DRadiation fog
Show answer & explanationAnswer & explanation
Correct answer: C. Clear air turbulence (CAT)
Clear air turbulence is most frequently found near the jet stream, particularly on the polar (cold air) side near the tropopause where wind shear is greatest due to the strong horizontal temperature gradient between air masses. CAT occurs in clear skies without visual warning, making jet stream areas a key hazard for high-altitude flight.
Why the other options are wrong
- A. Thunderstorms are convective phenomena driven by instability and moisture, not directly by jet stream shear.
- B. Freezing drizzle results from supercooled droplets in low-level stratus clouds, unrelated to jet stream dynamics.
- D. Radiation fog is a surface-based phenomenon from nighttime cooling, unrelated to upper-level jet stream activity.
Jet Stream and CAT
The jet stream is a narrow band of strong winds near the tropopause, generally moving from west to east, strongest in winter, forming where air masses of contrasting temperatures meet; it is a primary source of clear air turbulence.
- Jet stream winds can exceed 200 knots in strong cases
- Strongest and lowest in winter, weaker and higher in summer
- CAT is most common on the cold/polar side of the jet core near tropopause breaks
Memory trick: 'Jet stream = a fast river of air with rapids of CAT along its cold-side banks.'