Prevailing Winds

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Prevailing Winds
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What is wind?

• Wind is a movement of air in the atmosphere. Some
  winds are local or regional meaning they cover a
  fairly small area
• Winds that affect large areas are called
  prevailing winds. They affect weather around the
  world.

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The Coriolis Affect

• http//www.youtube.com/watch?vmcPs_OdQOYU
• The appearance of changing direction of winds in
  the upper atmosphere

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Solar Heating and Wind

• Solar energy strikes most directly near the
  equator.
• The warm air rises and expands leaving behind an
  area of low pressure. When the warmed air
  reaches the tropopause it moves northward.
• It eventually becomes cold and more dense around
  30º latitude and begins to sink creating an area
  of high pressure. Air at the surface moves from
  this high pressure area the low pressure near the
  equator. The air twists to the right from the
  coriolis effect causing the northeast trade winds.

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Pressure and Wind

• When the sun warms the air, the air expands, gets
  lighter, and rises.  Cooler, heavier air blows to
  where the warmer and lighter air was
• wind usually blows from areas of high air
  pressure to areas of low pressure.
• If the high pressure area is very close to the
  low pressure area, or if the pressure difference
  (or temperature difference) is very great, the
  wind can blow very fast.

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Jet Streams

• The major jet streams on Earth are westerly winds
  (flowing west to east).
• Jet streams form near boundaries of adjacent air
  masses with significant differences in
  temperature, such as the polar region and the
  warmer air towards the equator

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Jet streams

• The strongest jet streams are the polar jets, at
  around 7-12 km (23,000-39,000 ft) above sea
  level, and the higher and somewhat weaker
  subtropical jets at around 10-16 km
  (33,000-52,000 ft). The northern hemisphere and
  the southern hemisphere each have both a polar
  jet and a subtropical jet.

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Effects of Prevailing Winds

• Distribute large amounts of solar energy across
  the world
• Cause a variety of precipitation such as snow and
  rain
• At the 30º where the cold dry air descends
  deserts form

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