WIND NOTES by cuiliqing


									WIND NOTES
           I. What is Wind?:

• Wind: the horizontal movement of air from an
  area of high pressure to an area of lower
• The movement of air is caused by differences in
  air pressure.
• The greater the pressure difference, the faster
  the wind moves.
           Measuring Wind
• Winds are described by their direction and
• Wind Vanes are used to determine wind
• Wind Speed is measured with an
• Wind Chill Factor measures cooling that
  combines temperature and wind speed.
              Local winds
• Are winds that blow over short distances.
• Are caused by the unequal heating of
  Earth’s surface within a small area.
             1. Sea Breezes
• Occurs along the shore of a large body of water
  like an ocean or lake.
• Are created during the day when solar radiation
  warms land faster than water.
• Air over land is heated by conduction.
• The heated air is less dense and is forced
  upward by cooler, denser air moving in from the
• Draw the sea breeze picture that is on the next
          2. Land Breezes
• Land breezes are created at night when
  land cools faster than water.
• Air over land becomes cooler and denser.
• The cool air over land pushes out over
  water and forces the warm air over water
• Draw the land breeze picture that is on
  the next slide.
       3. Mountain Breezes
• In the evening, the mountain slopes cool
  the surrounding air more quickly than the
  air found lower in the atmosphere. This
  creates a high pressure as air becomes
  more densely packed. The resulting high
  pressure causes winds to blow down the
  mountain towards the valley floor.
           4. Valley Breezes
• During the day, the surface of the mountain
  heats the air high up in the atmosphere, quicker
  than the valley floor can.
• As the warmer air expands a low pressure is
  created near the top of the mountain. This
  attracts the air from the valley, creating a breeze
  that blows from the valley floor up towards the
  top of the mountain.
• eagles, hawks, condors, and vultures float on
  these breezes to preserve their energy.
Mountain and Valley Breezes
•In the daytime we typically see valley
breezes, as winds blow from the valley up
towards the mountains.
•In the night we often see mountain breezes,
as winds travel from the mountains, down
towards the valleys.
        5. Seasonal Winds
• Seasonal winds change with the seasons.
             a. Monsoons
• Monsoons occur in tropical areas.
• 1. In Winter: land is cooler than the
  ocean causing the air to flow away from
  land bringing dry weather.
• 2. In Summer: land is warmer than the
  ocean and the air blows toward land
  bringing extremely heavy rain. (wet)
          III. Global Winds
• Are winds that blow steadily from specific
  directions over long distances.
• Are created by the unequal heating of
  earth’s surface.
• Occur over large areas
• Why does
  Earth and
  heat unevenly?
• The uneven heating is due to Earth’s
  curved surface. Since it isn’t flat, different
  areas receive different amounts of solar
  radiation. The equator receives the most
  and the poles receive much less.
• Differences in air pressure are created by
  temperature differences.
• Heated air is less dense (lighter) than cold
  air, which is more dense (heavier).
• The warmer air gets pushed upward by
  the cold air creating the general circulation
  of air around Earth.
• Giant convection currents are produced in
  the atmosphere by the temperature
  differences between the equator and the
• Air pressure is greater at the poles and
  lower near the equator.
• At the surface, the winds blow from the
  poles towards the equator.
• Higher in the atmosphere, the air flows
  away from the equator toward the poles.
            Coriolis Effect
• The apparent curving of the path of a
  moving object from an otherwise straight
  path due to earth’s rotation.
    IV. Global Wind Belts
The major global wind belts are
  the trade winds, the polar
  easterlies, and the prevailing
             1. Doldrums
• Areas where the air seems motionless
  because it is moving almost straight up.
• Located along each side of the Equator.
• Ships avoid these areas since there is no
  wind to fill their sails.
• Have you ever had the doldrums?
         2. Horse Latitudes
• At about 30° north and 30° south latitude,
  sinking air creates an area of high
• Weak winds form as a result of the sinking
  air making it difficult for ships to sail.
• Sailing ships that carried horses in this
  area would throw the horses overboard to
  save drinking water for the sailors.
       3. Trade Winds
• provided a dependable route for trade
  in the days of the great sailing ships.
• Located between the equator and 30
  latitude North or South
• Blow to the southwest in the Northern
  Hemisphere and to the northwest in the
  Southern Hemisphere.
     4. Prevailing Westerlies

• Responsible for the movement of weather
  systems across the US and Canada
• In the Southern Hemisphere, they blow
  from the northwest to the southeast.
• In the Northern Hemisphere, from the
  southwest to the northeast.
        Westerlies, contd.

•   blow in the opposite direction from the
    trade winds.
•   Used by sailors to sail from the Americas
    to Europe.
•   Located between 30 and 60 latitude
    North and South of the Equator.
       5. Polar Easterlies
• Located from 60 to 90 latitude North and
• Blow from northeast to southwest near the
  North Pole and from southeast to
  northwest near the South Pole.
              . Jet Streams
• Are high altitude winds.
• Narrow belts of strong winds that blow
  near the top of the troposphere.
• 2 jet streams in each hemisphere that
  blow from W to E at the upper boundaries
  of the prevailing westerlies.
• Resemble fast moving rivers.
• Position changes daily and seasonally in
  latitude and altitude.
How do the jet streams
help/hinder air travel?
  Wind Observation Homework
• Make 3 wind observations between now and
• Your observations must include the time of day,
  the temperature, weather conditions and
  evidence of wind. Try to make observations at
  different times during the day.
• Your evidence can be things feeling it, seeing it,
  hearing it, etc. Be sure to describe your

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