Transcript Prevailing Winds

Prevailing Winds
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.
The Coriolis Affect
• http://www.youtube.
com/watch?v=mcPs
_OdQOYU
• The appearance of
changing direction
of winds in the
upper atmosphere
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.
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.
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
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.
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