FAA Aircraft Dispatcher (ADX)MeteorologyHard
A dispatcher is reviewing conditions at a coastal airport during a clear, calm summer afternoon. Surface winds shift from a light offshore flow in the early morning to a steady onshore flow by early afternoon. What phenomenon explains this daily wind shift?
- ASea breeze circulation caused by differential heating of land and water
- BKatabatic drainage flow from nearby high terrain
- CFrontal passage of a fast-moving cold front
- DMountain wave circulation induced by upper-level jet stream winds
Show answer & explanationAnswer & explanation
Correct answer: A. Sea breeze circulation caused by differential heating of land and water
During the day, land heats faster than water, causing air over land to rise and creating a local pressure gradient that draws cooler, denser air from over the water onshore—the sea breeze. This diurnal cycle typically develops by early-to-mid afternoon and reverses at night as a land breeze once the land cools faster than the water.
Why the other options are wrong
- B. Katabatic winds are drainage winds flowing downhill at night due to cooling, unrelated to a daytime onshore shift.
- C. A cold front passage would show broader synoptic-scale wind and pressure changes, not a routine daily diurnal shift.
- D. Mountain wave circulation relates to strong winds over terrain in stable air, not coastal diurnal heating cycles.
Sea Breeze Circulation
A local wind circulation caused by differential heating between land and water, with cooler air flowing onshore during the day.
- Land heats faster than water, creating a thermal low over land by afternoon
- Cooler, denser marine air flows onshore to replace rising warm air
- Reverses at night as a land breeze once land cools faster than water
Memory trick: Land heats fast, air rises, sea air rushes in—'sea breeze by three.'