Climates

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Climates
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What is Climate

• Climate is an average of weather conditions in a
  region over a long-term period of time.
• Weather is the short-term condition of the
  atmosphere over a region.

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Global Climate

• Global climate is determined by the interaction
  of solar energy with the Earths surface and
  atmosphere
• - by conditions of temperature and humidity.
• Climate is important is determining
• habitability
• land use
• Effect of climate is the availability of water at
  the surface and within the ground.

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The Water Cycle and Climate

• The water cycle involves the transfer of moisture
  between the land and sea, and between different
  latitudes.
• Since climate is determined by the amount of
  moisture and the potential for evapotranspiration,
  climate is tied to the water cycle.

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The Earths Water CycleIs a Closed System
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Latitude Affects Moisture Exchange

• Some latitudes have a surplus of precipitation
  over evaporation, other latitudes have a
  precipitation deficit.
• 3 main belts of surplus are
• the equatorial zone 0o to 10o North and South
• mid-latitude zones 40o to 70o in each hemisphere
• 2 main belts of deficit are
• 10o to 40o in each hemisphere

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Insolation

• INcoming SOLar radiATION
• Insolation is the term that refers to the amount
  of radiation from the Sun that is received by the
  Earth.
• Intensity of insolation is the rate at which
  solar energy is received by a given area of the
  Earths surface per unit of time.

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Intensity and Area

• Intensity of insolation is inversely related to
  the area of the Earths surface receiving it.
• As area gets bigger, intensity gets lower.

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Intensity vs Area
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Factors Affecting Insolation

• Some of the many factors that affect insolation
  are
• Angle of insolation
• Type of surface
• Length of time insolation is received
• Atmospheric conditions

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Angle of Insolation

• The angle which the Suns rays strike the surface
  is called the angle of insolation.
• The angle can be from 0o to 90o.
• Rays at a 90o angle are called direct, or
  vertical, rays.
• Areas receiving more direct rays will have higher
  temperatures.

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Angle of Insolation
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Time and Intensity

• Angle of the Sun varies with time, so time will
  affect intensity.
• At sunrise and sunset the angle of the Suns rays
  is the least and so the intensity is least.
• At noon the Suns rays are at their greatest
  angle (most direct) and so the intensity of
  insolation is also the greatest.

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Time and Angle
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Earths Shape Affects Intensity of Insolation

• Since the Earth is an oblate sphere, there is
  only one location that receives vertical rays
  from the sun.
• The more you move away from the direct rays, the
  lower the angle of the rays and the lower the
  intensity.

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Intensity of Insolation Diagram
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Vertical Rays at Summer in Northern Hemisphere
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Seasons and Intensity of Insolation

• Intensity of isolation varies with the seasons of
  the year.
• Seasons are caused by the tilt of the Earths
  axis and the revolution around the Sun.

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Seasons of the Earth
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Latitude and Intensity of Insolation

• At noon on the date of the equinoxes, the sun is
  directly over the equator.
• At this time the angle of the sun is the same as
  the observers latitude.

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Seasonal Angles of the Sun
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Duration of Insolation

• The duration of insolation is the number of
  daylight hours at a given location.
• Daylight hours vary with latitude and time of
  year.
• There is a direct correlation between angle and
  intensity of insolation and duration of
  insolation.
• Ex. Jun. 21 in Northern Hemisphere when angle and
  intensity are greatest, duration is longest.

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Length of Day / Duration
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Radiative Balance

• Radiative balance exists when a substance gains
  the same amount of radiation as it gives off.
• The Earth continuously receives insolation and
  radiates infrared energy from its surface.

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Maximum and Minimum Temperatures

• Maximum radiative energy reaches the Earth when
  the angle and intensity of insolation are the
  greatest.
• On a daily basis this is at solar noon (when the
  Suns rays are most direct).
• Highest temperatures are after this time.
• Earth begins to receive more energy than it gives
  off (reradiates).
• Highest temperatures occur mid-afternoon.
• Lowest temperatures occur just after sunrise.

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Time of Year

• In the Northern Hemisphere the hottest time of
  year is after June 21 (greatest angle and
  duration of insolation).
• Hottest time of year is in August when the
  amounts of incoming and outgoing energy are in
  radiative balance.
• Coldest time of year is after Dec 21 (least angle
  and duration) occuring in February.

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Duration and Temperature

• Temperature at the surface is directly related to
  duration of insolation.
• The longer the duration the higher the
  temperature
• Note the shortest days also have the lowest
  angle.

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