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					Climate and
 Climate- the average, year-after-year
  conditions of temperature, precipitation,
  winds and clouds in an area.
 The main factors that affect precipitation
  are prevailing winds and the presence of
 Rising warm air cools, and its water vapor
  condenses and falls as rain or snow on the
  windward side of the mountain (the side
  the wind hits). The land on the leeward or
  downwind side of mountains is in the rain
  shadow and gets little precipitation.
 The main factors that influence
  temperature are latitude, altitude, and
  distance from large bodies of water and
  ocean currents.
             Climate Zones
• Tropical Zone- area near the equator, with
  warm climate, it receives direct sunlight all
• Polar Zone- cold climates because the
  sunlight strikes the ground at a low angle.
• Temperate Zone- between tropical and
  polar zones, warm summers and cold
            Climate Types
• Marine Climate- relatively warm winters
  and cool summers, near large bodies of
• Continental Climate- inland areas, cold
  winters and warm or hot summers.
• Microclimate- small area with specific
  climate conditions different from
  surrounding areas, affected by the same
  conditions that create regional climates.
 Seasons- caused by tilt of Earth’s axis as the
  Earth travels around the sun.
        What causes winds?
• Air is a fluid. It can move easily from place
  to place
• Caused by difference in air pressure
  – High to Low

• Wind- horizontal movement from area of
  high pressure to area of low pressure.
       Convections currents
• Cause of winds

• Air over heated surface becomes less
  dense and rises.

• Cooler air comes in to replace the rising
  Warmer air rising up from a low pressure system and
cooler air sinking into a high pressure system. Notice the
  air at the surface is moving from high to low pressure
              Local winds
• Winds that blow over short distances

• Caused by convection currents due to
  unequal heating of Earth’s surface within a
  small area

• Form only when no winds are blowing
  from far away
         Sea breeze( Daytime)
    Takes more energy to heat up water
    than land.
•   Land heats up faster and air above land
    becomes less dense and rises.
•   Low pressure above land
•   Cool air ( high pressure) from above the
    water blows in toward land to replace the
    rising warm air
•   Called a sea breeze
         land breeze (night)
• At night, it is reversed.
• Land cools more quickly than water
• Warm air above water become less dense
  and rises
• Cooler air over the land moves in toward
  the water to take the place of the rising
  warm air
Sea breeze in action over Florida. Darker area is the water.
Notice the line of clouds that forms near the eastern coast
of Florida and advances inland, with mostly clear skies
behind it.
             Global winds
• Winds that blow steadily over long
• Also created by unequal heating of earth’s
• Depend on how sunlight strikes the earth.
• Equator:
   – at mid day, sun is
     directly overhead.
   – Direct rays heat the
     surface intensely
   – Temperatures
     much higher
• Toward north and
  south pole:
   – Rays strike at lower
   – Energy spread out
     over larger areas
   – Heats surface less
   – Temperatures
     much lower
      Global convection currents
• Temperature differences between equator
  and poles cause huge convection currents

•   Warm air rises at equator (low pressure)
•   Cool air sinks at poles (high pressure)
•   Winds blow from High to low pressure
•   Blow from poles to equator
               Coriolis effect
• Global winds do not
  blow in straight lines
• The earth rotates as
  wind blows, making it
  seem as if the winds
  are curving
• Called the Coriolis
• In upper part of the
  picture, the black
  object appears to
  move in a straight
  line. However, the
  observer (red dot) in
  lower part of the
  picture sees the
  object as following a
  curved path.
• This curve is due to
  the disk rotating
  under the ball as it
• In the northern
  – Global winds gradually
    turn toward the right
  – Winds are deflected to
    the right of where they
    were intended, had
    there not been any
    spin to the earth.
• In the southern
  – Winds curve slightly to
    the left of where they
    were intended
          Global wind belts
• Coriolis and other factors combine to
  produce a pattern of calm and wind belts
  around the earth

• Major wind belts:
  – Trade winds
  – Westerlies
  – Easterlies
• Near equator, between 0-30 degrees lat.
• Rising air, low pressure
• Cool air moves into area, warmed rapidly,
  and rises.
• Warms so fast, air doesn’t have an
  opportunity to move very far before it rises
• Winds very weak near equator-
              Horse latitudes
• Warm air at equator rises and divides
• Some flows north, some flows south
• At about 30 latitude, air stops moving toward
  poles and sinks.
• Forms another belt of calm air-HORSE
  – Hundreds of years ago, sailors got stuck in these
    calm waters and ran out of food and water for their
    horses and had to throw them over.
             Trade winds
• Blow from horse latitudes to the equator
• When cold air sinks, produces high
• High pressure wants to move to an area of
  low pressure--the equator!!
• These winds that are blowing toward the
  equator are deflected west because of the
  coriolis effect
        Prevailing Westerlies
• Blow away from the horse latitudes(30)
  toward the poles, to about 60 degrees

• turned toward the east by coriolis effect

• Blow from west to east--WESTERLIES
           Polar easterlies
• Cold air near poles sinks and flows back
  toward lower latitudes

• Coriolis shifts these winds to west

• Wind goes from East to west--
                     Jet streams:
• About 10 Km above
  earth’s surface
• Bands of high speed
• Blow from west to east at
  about 200 to 400 Km/hr
• Airplanes aided by jet
  streams when traveling
   – pilots save fuel and time
          Effect on climate
• Low pressure zones are associated with
  high rainfall
Climate zones
Ocean currents
            Ocean Currents
• Like the circulation of air, the circulation of
  the world's oceans is also very important
  in the distribution of energy.
• Warm ocean currents are corridors of
  warm water moving from the tropics pole
  ward where they release energy to the air.
• Cold ocean currents are corridors of cold
  water moving from higher latitudes toward
  the equator.
Surface Currents
            Surface currents
• Currents flow in complex patterns affected by
  wind, the water's salinity, heat content,
  topography, and the earth's rotation.

• A distinct correlation between the pattern of
  ocean currents and the air circulation above
  them can be made.

• winds drag across vast areas of sea and pull
  the surface water in the same direction.
Gulf stream
       • The Gulf Stream, is a
         powerful, warm, and swift
         Atlantic ocean current that
         originates in the Gulf of

       • The Gulf Stream influences the
         climate of the east coast of
         North America from Florida to
         Newfoundland, and the west
         coast of Europe.

       • Its extension toward Europe
         makes winters warmer than
         they otherwise would be at
         those latitudes.

       • The Gulf Stream is largely
         driven by the wind.
Gulf stream at its origin at the tip of Florida.
It is the fastest ocean current in the world!!!
Deep ocean currents
          • Cold, salt-laden water
            is heavier than warm
            water and sinks into
            the depths of the
          • Warmer water
            masses flow in to
            replace it.
          • These then cool and
            follow the sinking
Deep ocean currents
Changing ocean currents
   and global winds:

  Effects on the climate
                   El Nino
• Periodically, a warm water event known as El
  Nino occurs in the tropical Pacific ocean.

• During this time, winds shift and push warm
  surface water toward the west coast of South

• Warm water replaces the cold water that usually
  rises from the deep ocean near the coast
• Upwelling of cold
  water that usually
  occurs along the west
  coast of coast of
  South America in a
  normal year
• Brings cold water
  from deeper regions
  to surface
• Cold, nutrient-rich
  water rises to replace
  the surface water
• Good for fishing in
                   El Nino
• This warm current appears around Christmas
  time along the coast of Ecuador and Peru (not
  good for their fishing industry!)

• can produce significant economic and
  atmospheric consequences worldwide

• occur every 3-7 years, lasting about one year

• Recent major events: 1982-1983 and 1997-1998

• The 97-98 event was the strongest ever
 El Nino - Animation of warm pool
• Notice the eastward movement of warm
  water (shaded red) from the western
  equatorial pacific to the eastern equatorial
    Sea Surface Temperatures
      during a normal year

• During a normal year, there is a large pool
  of warm water in the western pacific.

• Low pressure in the western pacific over
  the warm water

• High pressure in the eastern pacific over
  the colder water
Normal year
              El Nino year
• Sea surface temp in the eastern pacific
  becomes warmer than normal

• High pressure (cold) shifts from the
  eastern pacific to the western

• Low pressure (warm) shifts from the
  western Pacific to the eastern pacific.

• has a large impact on the precipitation
  distribution around the pacific basin
El Nino year
                 La Nina
• After the El Nino phase, La Nina follows

• La Nina refers to the unusually cold water
  that is found in the eastern pacific ocean
• Misc. maps

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