FAA Airline Transport Pilot (ATM)Meteorology and Weather ServicesMedium
A pilot based at a small airport in a mountain valley notices that on clear, calm nights a steady, cool wind consistently flows downslope from the surrounding higher terrain into the valley, and this wind dies out shortly after sunrise. This local wind is best described as a
- AChinook wind
- BFöhn wind
- CSea breeze
- DKatabatic (drainage) wind
Show answer & explanationAnswer & explanation
Correct answer: D. Katabatic (drainage) wind
Katabatic (drainage) winds develop when air near elevated slopes cools radiationally at night, becomes denser, and flows downhill into valleys under gravity; they typically dissipate after sunrise heating disrupts the temperature gradient.
Why the other options are wrong
- A. A Chinook is a warm, dry downslope wind on the lee side of mountains, not a nighttime cooling-driven wind.
- B. Föhn wind is the European term for the same warm downslope phenomenon as a Chinook, not a cold drainage wind.
- C. A sea breeze results from differential heating between land and water during the day, unrelated to mountain terrain at night.
Katabatic (Drainage) Wind
A cool, downslope wind caused by radiational cooling of air along elevated terrain, which becomes dense and flows downhill into valleys, typically at night.
- Occurs under clear, calm nighttime conditions
- Air cools and becomes denser along slopes
- Dissipates after sunrise as heating begins
Memory trick: Katabatic = 'cat crawling downhill at night' — cold air creeping down slopes.