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INSOLATION AND THE SEASONS

INSOLATION AND THE SEASONS. Topic 6 in Review Book. Energy from the sun drives:. global wind patterns ocean currents the water cycle. Without solar energy:. Earth would be a frozen wasteland All the water and gases in the atmosphere would only be found in the solid phase.

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INSOLATION AND THE SEASONS

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  1. INSOLATION AND THE SEASONS Topic 6 in Review Book

  2. Energy from the sun drives: • global wind patterns • ocean currents • the water cycle

  3. Without solar energy: • Earth would be a frozen wasteland • All the water and gases in the atmosphere would only be found in the solid phase. • Earth and the moon would be completely dark.

  4. The rate at which energy is radiated is called the • intensity of radiation • In general, the higher the temperature, the shorter the wavelength at which maximum intensity occurs.

  5. The sun’s maximum intensity of radiation occurs in the • visible wavelength

  6. INSOLATION • is the portion of the sun’s electromagnetic energy that is received by the earth. • Insolation stands for: • Incoming • Solar • Radiation

  7. Intensity of Insolation • is the relative strength of the sun’s radiation that reaches a specific area of Earth in a specific amount of time

  8. Effects of the atmosphere • The atmosphere is mostly transparent to visible light. • Consequently this is the wavelength most received by the surface of the Earth.

  9. Most of the ultraviolet radiation from the sun is absorbed in the ozone layer • This layer is located 20 to 50 km above Earth’s surface • Concentrations vary seasonally with the smallest concentrations occurring in the spring.

  10. The ozone layer is being depleted (decreased) due to the chemical reaction between ozone (O3) molecules and chlorofluorocarbons (CFCs) • This reaction creates “ozone holes” that tend to be found near the poles

  11. The depletion of the ozone layer results in greater amounts of ultraviolet radiation reaching the surface of the earth. • UV radiation is very harmful – causing skin cancer in humans and tissue mutations in plants and animals

  12. Water vapor, carbon dioxide (CO2) and methane (CH4) absorb incoming and radiated infrared radiation. • Increases in these gases result in an increase in atmospheric temperature – “global warming”

  13. These gases act like the glass walls of a greenhouse… • Visible wavelengths are absorbed by the earth’s surface and reradiated as infrared wavelengths • which are absorbed by the water vapor, CO2 and CH4 in the atmosphere • preventing the natural cooling of the earth’s surface

  14. UV Ozone layer IR VIS CO2 IR

  15. Particulates in the atmosphere (called aerosols) such as dust, bacteria, salts, volcanic ash, air pollutants, pollen etc. can reflect or scatter insolation decreasing temperatures

  16. FACTORS THAT INFLUENCE INTENSITY OF INSOLATION • The shape of the earth: • The curvature of the earth causes the angle of insolation to vary

  17. Latitude: • influences angle of insolation. • As latitude increases • angle of insolation decreases • which decreases the intensity of insolation

  18. Seasons: • determine which areas receive the most direct rays of insolation and for what duration • In the northern hemisphere, summer months have the greatest intensity and duration of insolation

  19. Time of day: • determines the angle of insolation. • Solar noon has the highest angle of insolation, therefore, the highest intensity

  20. TEMPERATURE AND INSOLATION • As intensity of insolation increases the amount of energy received by the area increases increasing the amount of energy absorbed increasing the temperature

  21. High altitude sun: • High intensity of insolation • More energy is absorbed • Resulting in high temperatures • Highest altitudes occur at solar noon and during the summer

  22. Low altitude sun: • Low intensity of insolation • Low temperatures (ineffective heating) • Occurs in the morning, evening and during the winter months

  23. TEMPERATURE LAGS • Air temperature depends on the relationship between the amount of insolation received and the amount radiated by the earth

  24. The cooler the surface, the less energy is radiated • High temperatures lag behind times of high intensity due to the fact that the surface must be warmed by the sun to radiate the energy and heat the atmosphere.

  25. Highest intensity: • solar noon and June • Highest temperatures: • after noon and July/August

  26. Radiative Balance • occurs when the amount of heat energy being lost through radiation is equal to the amount of heat energy gained by insolation

  27. Temperatures increase when the amount of heat energy gained by insolation is greater than the amount lost through radiation • The earth takes in more heat energy than it gives off

  28. Temperatures decrease when the amount of heat energy gained by insolation is less than the amount lost through radiation • The earth gives off more than it takes in.

  29. ATMOSPHERIC TEMPERATURE • The radiation of infrared energy from the surface of the earth heats the atmosphere. • When the surface of the earth is warmer than the air above it, the heat energy is transferred to the air and circulated through the atmosphere by convection currents.

  30. HEATING OF EARTH’S SURFACES • Land surfaces are dark and rough and have a low specific heat • This means that they readily absorb and radiate heat energy and change temperature rapidly

  31. Water surfaces are • transparent and reflective and have a high specific heat • This means that they reflect more energy than they absorb and heat up and cool down slowly

  32. LAND SURFACES HEAT UP AND COOL DOWN FASTER THAN WATER SURFACES!!!

  33. CLIMATE CHANGE • Long-term changes in the radiative balance of the earth can result in climate changes.

  34. ICE AGES ANDINTERGLACIAL WARM PERIODS • Ice ages occur when the earth radiates more energy than it receives. • When this occurs, glaciers advance through mid-latitudes

  35. The last ice age began ~ 1.6 million years ago and lasted until 10 thousand years ago. • We are now believed to be in an interglacial warming period – the time between ice ages when the earth receives more energy than it radiates

  36. EL NIÑO AND LA NIÑA • El Nino is an unusual warm period caused by the change in the ocean currents of the eastern Pacific Ocean… these currents are normally cool currents and when replaced by warm currents result in warmer temperatures

  37. La Nina is a similar event, but the cool current is made exceptionally cold resulting in much lower temperatures.

  38. GLOBAL WARMING AND HEAT WAVES • World wide temperatures have increased from the early 1980s. Scientists are unsure as to whether this is a natural warming trend or if it is an anthropogenic (man-made) problem.

  39. A heat wave is an extended period of exceptionally warm temperatures that can result in health issues such as hyperthermia. • Prevention steps include: • limit outdoor exercise • drink plenty of water • stay in shaded areas when outdoors • stay in air conditioned locations

  40. CAUSES OF TEMPERATURE SHIFTS • Changes in the output of the sun • Times of increased sunspot activity are linked to times of increased temperature due to the increase in electromagnetic energy released by the sun during increased sunspot activity

  41. Changes in Earth’s orbit and tilt • Over thousands of years, the tilt of the earth changes by a few degrees which influences the intensity of insolation at each latitude

  42. Also over thousands of years, the eccentricity of Earth’s orbit changes by a minor amount which would change the distance between the earth and the sun.

  43. VOLCANIC ERUPTIONS • Volcanic eruptions disperse ash, dust and sulfur compounds into the atmosphere. • These are distributed over vast areas through the atmosphere remaining there for extended periods of time

  44. These particles decrease the transparency of the atmosphere decreasing insolation and globally decreasing temperatures

  45. ANTHROPOGENIC CAUSES • Humans have an impact on climate… • Deforestation and desertification cause climates to be hotter and drier

  46. Deforestation is the cutting down of forests. • Forests absorb more insolation – when cut down, more insolation is received by the earth. • Less trees = less transpiration = less moisture in the atmosphere = less precipitation

  47. Desertification is the expansion of desert regions due to the destruction of grasslands. • This can occur due to overgrazing of livestock • Less plants = less transpiration = less precipitation • Deserts heat up faster than grasslands = higher temperatures

  48. URBANIZATION • The development of land reduces plants… • industries, transportation and energy needs produce “greenhouse gases”… • all of which increases temperatures

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