The Journey of Flight.pdf - Valkyrie Cadet

heated air rising upward which cause advection currents (wind) to flow from the water over the warmer
land during the day. During the night, convection currents develop over the warmer-than-land water
and cause the wind to blow from the land toward the water. This phenomenon is known as the land and
sea breeze.
Local air circulation of limited scope is caused by variations in the Earth’s surface. Some surfaces—
such as sand, rocks, plowed areas and barren land—give off or reflect a great amount of heat.
Other surfaces—such as meadows, planted fields and water—tend to retain heat. Rising air currents
are encountered by aircraft flying over surfaces that give off considerable heat, while descending air
currents are encountered over surfaces that tend to retain heat.
Moving air flowing around obstructions tends to break into eddies. On the leeward (opposite of
the windward) side of mountains there are descending air currents. Such conditions cause turbulent
air. The stronger the wind, the greater the descending air currents and turbulence. Aviators flying into
the wind toward mountainous terrain should place enough distance between their aircraft and the
mountaintops to avoid dangerous descending air currents.
Land-sea Breeze Phenomena
Thermals, advection currents, convection currents, wind, updrafts and downdrafts affect air movement.
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