"INSOLATION AND THE SEASONS TOPIC 6 page 85106

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"INSOLATION AND THE SEASONSTOPIC 6(page
85-106)
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6-1) SOLAR RADIATION AND INSOLATION

• insolation - (incoming solar radiation)
• the sun's energy that is received by Earth.
• maximum intensity occurs as visible light.

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Effects of Earth's Atmosphere on Insolation

• insolation may be
• absorbed,
• reflected, or
• scattered
• before it reaches the Earth's surface.

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1 - ABSORPTION

• SHORT WAVE ENERGY
• Most of the short wave radiation is
• absorbed by the atmosphere.
• Ultraviolet (UV) radiation is
• absorbed by the ozone layer.
• ozone
• form of oxygen gas. (03)
• destroyed by (CFCs) chlorine and fluorine gases.
• less ozone more UV radiation striking the
  Earth's surface.
• UV radiation causes skin cancer.

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• LONG WAVE ENERGY.
• Is absorbed by greenhouse gases.
• Greenhouse gases
• carbon dioxide
• water vapor
• methane gas

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2 - REFLECTION SCATTERING

• clouds reflect insolation back into space.
• aerosols reflect, scatter, and absorb insolation.

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aerosol

• finely dispersed solids and liquids in the air.
• examples ice crystals, water droplets, dust,
  volcanic ash, pollution.
• As the amount of aerosols increases
• more insolation is scattered
• the amount of insolation reaching the ground is
  less
• the temperature will decrease.

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Balance of Energy

• the amount of energy from insolation is equal to,
  the amount of energy radiated from the Earth.
• therefore, Earth's temperature and heat are
  balanced.

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Factors Affecting Absorption and Reflection at
Earths Surface.
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1 - Angle of Insolation

• Angle of Insolation (angle of incidence)
• the angle at which the insolation strikes Earth's
  surface.

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The greater the angle of insolationmore energy
is absorbed and less energy is reflected.

• the higher the sun is in the sky, the greater the
  angle of insolation.
• noon sun almost overhead large angle of
  insolation.
• early morning or late evening low in sky low
  angle of insolation.

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diagram
high angle
energy focused on small area
intense heating
low angle
energy spread over a large area
less heating
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2 - Surface Characteristics.

• Texture and color
• rough surfaces and dark colors absorb more
  insolation.

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3 - Change of State and Transpiration

• When energy is involved in change of state or
  transpiration.
• it is not available to raise the temperature of
  Earth's surface.

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4 - Land vs Water

• Liquid water will heat up and cool off more
  slowly than an equal area of land.

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4 Reasons why Water heats more slowly than land.

• water has a higher specific heat.
• insolation can penetrate water (it only heats the
  surface of the land).
• water can flow, so energy can be distributed by
  convection currents.
• energy is used to evaporate water.

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THE GREENHOUSE EFFECT

• infrared energy, from the Earth, is absorbed by
  gases in the atmosphere.
• greenhouse gases carbon dioxide, water vapor
  and methane.
• Greenhouse gases reduce the amount of energy that
  is lost to space.
• If less energy is lost, Earth's atmosphere
  becomes warmer.
• As more of these gases are added to the
  atmosphere, more energy is absorbed (global
  warming).

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Greenhouse Effect Diagram

• Short-wave radiation (insolation) passes through
  the atmosphere,
• Long-wave radiation from the Earth (terrestrial
  radiation) is absorbed by the atmosphere.
• diagram

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• Global Warming
• an increase in average Earth temperatures.
• Caused by
• the burning of wood and fossil fuels.
• Results..
• Rising sea level.
• Shifting of climatic zones.

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Review Book Complete Review Questions page
88, 1-10.
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6-2) VARIATION IN INSOLATION
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Insolation can vary in 2 ways

• intensity (strength).
• duration (length of time)

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Five factors that affect Intensity

• intensity
• the rate at which solar energy is received.

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• Angle of Insolation
• At 90 o (perpendicular)
• maximum intensity (energy is concentrated).
• At angles close to 0 o
• minimum intensity (energy is spread out).

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• 2) Earth's Shape
• At any given time, there is only one location
  where the angle of insolation is 90o. (maximum
  intensity)
• For every degree of latitude (N or S of that
  location) the angle of insolation is one degree
  less. (intensity is less)
• Examples

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• 3) Latitude.
• The maximum intensity of insolation occurs near
  the equator.
• The noon sun is always close to overhead.

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• 4) Time of year (Seasons)

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SPRING
March 21
Equinox
SUMMER
WINTER
SUN
Dec 21
June 21
Solstice
Solstice
FALL
Sept 23
Equinox
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Equinox (March 21 Sept 23)

• Maximum intensity of insolation is at
• 0 o Latitude (the equator).
• Duration
• 12 hours light and 12 hours of darkness,
  everywhere.
• diagram

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day
night
Suns rays
equator
0o
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Summer Solstice (June 21) "first day of summer"

• Maximum intensity of insolation is at
• 23 1/2 o N Latitude (Tropic of Cancer).
• Duration
• North Pole, 24 hours of daylight.
• South Pole, 24 hours of darkness.
• diagram

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day
night
90.0o -23.5o
66 ½ oN
23 ½ o N
0o
Suns rays
equator
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Winter Solstice (December 21) "first day of
winter"

• Maximum intensity of insolation is at
• 23 1/2 o S Latitude (Tropic of Capricorn).
• Duration
• South Pole, 24 hours of daylight.
• North Pole, 24 hours of darkness.
• diagram

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day
night
66 ½ oN
equator
Suns rays
0o
23 ½ o S
66 ½ oS
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5) Time of Day

• Maximum angle and intensity of insolation occurs
• at solar noon.

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Variation in Duration of Insolation

• duration amount of time.
• time between sunrise and sunset.

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• Duration is determined by.
• Latitude and Season.
• In the Northern Hemisphere
• Longest day of the year..
• Summer Solstice (June 21)
• Shortest day of the year
• Winter Solstice (December 21)
• 12 hours daylight 12 hours dark
• Spring Fall Equinox (March 21 Sept 23)

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Relationship of Surface Temperature to Insolation

• When energy is being gained at a greater rate
  than it is being lost, Earth's surface
  temperature
• rises.
• Greater intensity and/or greater duration usually
  means greater temperature.

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Times of Maximum Minimum Yearly Temperature.

• The date for maximum and minimum temperatures
  occurs
• after the date for maximum and minimum
  insolation.

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In the Continental United States

• Greatest intensity of insolation occurs on June
  21 but ..
• the highest temperature occurs late July or early
  August.
• reason after June 21 the surface still receives
  more energy than it loses.
• Minimum insolation occurs on Dec. 21
• lowest temperature occurs in late January or
  early February

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Times of Maximum and Minimum Daily Temperature.

• Maximum intensity of insolation occurs at..
• solar noon.
• The hottest part of day occurs in
• mid-afternoon.
• Minimum intensity of insolation occurs
• after the sun sets.
• Coolest temp occurs
• just after sunrise.

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Answer Review Questions 11 - 31 on page 93.
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6.3) HEAT BUDGET AND CLIMATE CHANGE.
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Earth's heat budget is the result balance between

• the radiation from the sun (insolation)
• the radiation Earth gives off to space.

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Examples of Climate Change.
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1) Ice Ages and Long, Warm Periods on Earth.

• ice ages - periods when glaciers advanced into
  the middle latitudes.
• interglacial periods - warmer periods that
  occurred between the times of glacial advance.

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2) El Nino and La Nina.
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El Nino -

• occurs every two to ten years.
• the normally cold waters of the eastern Pacific
  Ocean (off western South America) are replaced
  with warmer waters.

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La Nina

• periods of time when there is exceptionally cold
  water.

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El Nino and La Nina cause major climatic
repercussions around the world.
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3) Global Warming.

• from the early 1980's there has been a trend of
  rising temperatures known as global warming.

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E) CAUSES OF HEAT BUDGET SHIFTS.
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1 - Changes in Solar Energy.

• the sun's energy output and related sunspot
  activity follow an 11 year cycle.
• sunspot - a darker region of the sun's surface.
• when there are more sunspots, the sun emits 0.1
  to 1.0 percent more energy.

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2 - Changes in Earth's Orbit and Axis Tilt.

• over thousands of years the tilt of Earth's axis
  changes a few degrees.

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• minor changes in the eccentricity of Earth's
  orbit.
• if these two things occur at the same
  timesummers may be cooler and winters warmer.
• these changes seem to correlate with the advances
  of glaciers during the Pleistocene Ice Age.

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3 - Volcanic Eruptions

• 1990 eruption of Mount Pinatubo, causes cooling
  of Earth's atmosphere.
• addition of aerosols makes Earth's atmosphere
  less transparent to insolation.

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4 - Human Causes.
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a) desertification

• overgrazing causes grasslands to become deserts.
• deserts heat up faster than grasslands, so the
  temperature of these areas increases.

Sahara Desert encroach on Nouakchott, the capital
of Mauritania.
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b) deforestation -

• insolation once absorbed by trees goes into
  heating Earth's surface.
• without trees, there is less transpiration which
  decreases the humidity of the atmosphere and
  therefore there is less precipitation.
• these areas become hotter and drier.

Loggers prepare to fell an 800-year-old red cedar
in the state of Washington.
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A burned clearing stands in grim contrast to
surrounding rain forest in Brazil.
Brazilian cattle graze in a pasture where rain
forest once stood.
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c) Addition of greenhouse gases to the
atmosphere.
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d) urbanization -

• clearing the land of plants and trees to
  construct buildings.

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Read pages 95 99Answer Review Questions p 99,
32-38.
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F) SEASONS.

• Seasonal changes result from variation in the
• angle of insolation.
• intensity of insolation.
• duration of insolation.
• There is little seasonal change near..
• the equator.
• Season changes are more extreme near .
• the poles.

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Causes of the Seasons.
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a) Tilt of Earth's Axis.

• Earth's axis is tilted 23.5o with respect to the
  plane of its orbit.
• perpendicular insolation from the sun shifts
  between 23.5o N (on June 21) and 23.5o S
  latitude (on Dec 21).
• a greater tilt would produce warmer summers and
  colder winters.
• no tilt would result in no seasons.

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b) Parallelism of Earth's Axis.

• the position of Earth's axis at any time is
  always parallel to its position at any other time
  (parallelism).
• the Northern end of Earth's axis always points
  towards the North Star (Polaris).

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c) Revolution Around the Sun.

• As Earth revolves around the sun, the direction
  of Earth's axis with respect to the sun
  varies..
• on June 21..the North Pole is inclined toward
  the sun.
• on Dec 21.. the South Pole is inclined toward
  the sun
• on March 21 Sept. 23 neither is inclined
  toward the sun.

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Effect of Earth's Elliptical Orbit.

• because the Earth's orbit is an ellipse, the
  distance between the Earth and the sun varies.
• these changes are too small to have any
  significant affect on the seasons.
• during Winter in the Northern Hemisphere the
  Earth is closest to the sun.

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Read pages 99 101.Answer Review Questions p
101, 39-48.Complete Questions for Regents
Practice p. 102.1-19