weather part 3: winds. winds caused by differences in air pressure due to unequal heating of the...
TRANSCRIPT
WeatherPart 3: Winds
Winds
•Caused by differences in air pressure due to unequal heating of the atmosphere• Two types – local
and global
Naming of Winds• Winds are named
after where they blow from.• So a north wind
comes from the north and blows toward the south• A sea breeze blows
from the sea on to the land.
East wind – • To?• From?Northwest wind• To?• From?Land Breeze• To?• From?
Local Winds
Sea Breeze- • The flow of air from sea to land• Happens during the day when the land warms
faster than the water• Also called an on-shore breeze
Local Winds
Land Breeze-• The flow of air from land to water• Occurs at night when the land cools off faster
than the water• Also call a land breeze
Local Winds
Monsoon –• A seasonal land and
sea breeze• During the part of the
year that it is a sea breeze it carries moisture that produces a rainy season with warm temperatures and huge amounts of rain.
• Major monsoon systems include West African and Asia-Australian monsoons.
Picture by lokenrc
This photo was taken on August 2, 2009 in South Dum Dum, Kolkata, WB, India.
Global Winds• Caused by direct
heating at the equator and indirect heating at the poles that causes higher temperatures at the equator.
• Warm air from the equator rises and moves toward the poles.• Cooler air at the
poles sinks and moves toward the equator.
Global Winds• Coriolis effect: the
apparent shift in the path of any fluid or object moving above the surface of the Earth due to the rotation of the Earth.
• In the Northern Hemisphere the Coriolis effect causes winds to curve to the right. South winds curve east and north winds curve west.• The opposite occurs
in the Southern Hemisphere where winds curve left.
Global Winds
Global Winds - Doldrums• At the equator (0°
latitude) • Surface winds are
calm• Warm rising air
produces a low pressure area that reaches many kilometers north and south of the equator
• Cooler air that flows in toward the low pressure area is warmed so rapidly it can’t move into the low pressure area, so any winds that do occur are weak.• Problem for sailing
ships
Global Winds – Horse Latitudes• At 30° latitude, north
and south, warm air from the equator begins to cool and sink• The sky is usually
clear with few clouds and little rain or wind.
• Called the horse latitudes, because ships becalmed here had to throw horses overboard when their food ran out
Global Winds – Trade Winds• Some of the air that
sinks at the horse latitudes flows back toward the equator causing warm, steady winds called trade winds• In the north the trade
winds blow from the northeast so they are called the Northeasterly Trades.
Global Winds – Prevailing Westerlies
• The cool, sinking air that continues moving toward the poles curves toward the east due to the Coriolis effect.• These winds are called
the prevailing westerlies.• Occur between 40° and
60° latitude• Often are particularly
strong
The area above Wakebarrow Scar and on Park Hill (in Great Britian) is over 200m above sea level and completely exposed to the prevailing westerlies. What few trees there are tend to be gnarled and wind-pruned. These hawthorns are reminiscent of old olive trees. © Copyright Karl and Ali and licensed for reuse under this Creative Commons Licence.
Global Winds – Polar Easterlies• Extremely cold air
flowing from the poles toward the equator. • Deflected west by
the Coriolis effect• Cold, weak winds• Cause many changes
in the weather that occur in the US
Jet Stream• Narrow belt of strong,
high-speed, high-pressure air• Flow from west to east at
altitudes above 12 km; at speeds as high as 350 km/hr• Wander up and down• Change season to season
and day to day• Affect the atmosphere
below them; create low-pressure areas
Measuring WindWind Direction:• Use a wind vane• The vane points into
the wind
Wind Speed:• Use an anemometer• Expressed in m/s,
mph, or knots (One knot = 1.852 km/h = one nautical mile = 1.151 mph)
© Copyright Miss Steel and licensed for reuse under this Creative Commons Licence
photo by Fergal of Claddagh on Flickr