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TOPIC 6: INSOLATION AND THE SEASONS

TOPIC 6: INSOLATION AND THE SEASONS. Solar Radiation and Insolation. Insolation – Incoming solar radiation Components of Insolation (by EM type) Infrared – 48% Visible Light – 44% Ultraviolet – 7%. Effects of Earth’s Atmosphere on Insolation. Absorption of EM

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TOPIC 6: INSOLATION AND THE SEASONS

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  1. TOPIC 6: INSOLATION AND THE SEASONS

  2. Solar Radiation and Insolation • Insolation – Incoming solar radiation • Components of Insolation (by EM type) • Infrared – 48% • Visible Light – 44% • Ultraviolet – 7%

  3. Effects of Earth’s Atmosphere on Insolation • Absorption of EM • UV rays are absorbed by the ozone layer. • However, there is a holein the ozonewhich allows UV to hit Earth and can cause cancer. • Infrared radiation absorbed by carbon dioxide, water vapor and methane • These are called greenhouse gasses

  4. Effects of Earth’s Atmosphere on Insolation • Reflection and Scattering • Conditions that cause HIGH REFLECTION of insolation • Clouds = lots of visible and IR reflected • Aerosols – small suspended particles in the atmosphere (dust, ice, water, ash) • Lots of aerosols cause lots of scattering of insolation • Low transparency of atmosphere

  5. Balance of Energy from Insolation • Half of the insolation hitting Earth’s atmosphere will reach Earth’s surface (land or water) • Transmitted through atmosphere • The Earth will re-radiate energy at longer wavelengths of EM usually in the form of heat (IR) • Earth is cooler than the sun

  6. Balance of Energy from Insolation • The amount of heat absorbed, over time, will EQUAL amount of heat radiated so that Earth’s surface temperature will tend to balance •  Dynamic equilibrium

  7. Factors Affecting Absorption and Reflection of Insolation • Angle of Incidence – the angle at which the sun’s energy hits the surface of the earth • Angle varies with latitude, time of day and season • The higher the angle of incidence the more energy is absorbed

  8. Factors Affecting Absorption and Reflection of Insolation • Characteristics of Earth’s Surface • More energy is absorbed if Earth’s surface is dark and rough

  9. Factors Affecting Absorption and Reflection of Insolation • Change of State (of water) and Transpiration • In general, when water is changing phase solid liquid  gas energy is absorbed • If energy needs to be absorbed to change phase it isn’t available to raise temperature of Earth’s surface

  10. Heating Land and Water • Land heats fasterover time than waterbecause land has a lower specific heat • Insolation can penetrate deeper into water. • Heating water is done by convection so water layers mix.

  11. Greenhouse Effect • Works on the idea that re-radiated energy is at a longer wavelength than incoming insolation • Greenhouse gasses (CO2, H2O, CH4) allow short wave EM in, but absorb longer wave EM that is re-radiated by Earth • The Greenhouse Effect keeps Earth’s temperature warm enough to support life

  12. Greenhouse Effect • Global Warming- an increase in the Earth’s average temperature • Due to an increase in CO2 and methane which traps re-radiated waves and raises Earth’s surface temperature • Causes include burning of fossil fuels and deforestation

  13. Variation of Insolation • Insolation varies 2 ways • Intensity • Duration

  14. Intensity of Insolation • Intensity of insolation- amount of solar energy received by an area over a certain amount of time • Intensity of insolation received by an area depends on the angle of incidence

  15. Angle of Incidence • Intensity of insolation is the greatest when the sun’s rays hit the surface of the earth at 90o

  16. Angle of Incidence • At angles less than 90o the insolation gets spread out over a larger area • The same amount of energy is spread out over a bigger area, so each part of that area receives less energy

  17. Angle of Incidence

  18. Angle of Incidence • As the angle of incidence increases, the intensity of insolation increases Intensity of Insolation Angle of Incidence

  19. Intensity of Insolation • The sun’s rays are parallel to each other as they approach Earth • If the earth was flat, all insolation would reach earth perpendicular to the surface (90o) • Since the earth is round the angle at which insolation hits the earth’s surface varies

  20. Angle of Incidence • As the latitude increases, the angle of incidence decreases Angle of Incidence Latitude

  21. Angle of Incidence • As the latitude increases, the intensity of insolation decreases Intensity of Insolation Latitude

  22. Intensity of Insolation

  23. Angle of Incidence • Only one location on earth receives the sun’s energy at 90o at a given time • The location varies throughout the year

  24. Intensity of Insolation • The angle of incidence varies for a given location throughout the year • Angle is the highest on the day that the sun is highest in the sky • Most intense insolation = summer solstice= June 21 for New York • Angle is lowest on the day that the sun is the lowest in the sky • Least intense insolation = winter solstice = Dec. 21 for New York

  25. Intensity of Insolation June 21 Dec 21 Dec 21 Summer Solstice in NYS Winter Solstice in NYS Winter Solstice in NYS

  26. Intensity of Insolation • The angle of incidence varies for a given location during the day • Angle is the highest a solar noon • Most intense insolation

  27. Intensity of Insolation

  28. Duration of Insolation • Duration of insolation - the length of time between sunrise and sunset • Duration of insolation varies for a given location throughout the year • Longest day = longest duration of insolation • June 21 in New York • Shortest day = shortest duration of insolation • December 21 in New York

  29. Duration of Insolation Sun’s path in summer in NYS June 21 Sun’s path in winter in NYS Dec 21

  30. Duration of Insolation • Duration of insolation is usually different at different locations on Earth • June 21 is the longest day in the Northern Hemisphere, shortest day in the Southern Hemisphere

  31. Duration of Insolation • Duration of insolation is 12 hours all over the earth on the equinoxes • March 21, September 23

  32. Duration of Insolation

  33. Insolation and Surface Temperatures • The intensity of insolation and the duration of insolation together determine the surface temperatures for an area • The more intense the insolation, the more energy an area receives, the higher the temperature • The longer insolation is received at an area, the more energy absorbed, the higher the temperature

  34. Insolation and Surface Temperatures

  35. Insolation and Surface Temperatures • The Earth heats up when it absorbs more energy than it radiates • When the energy gained by an area is GREATER than the energy it radiates, its temperatures will rise • When the energy gained by an area is LESS than the energy it radiates, its temperatures will fall

  36. Minimums and Maximums of Temperature • The highest temperatures of the year for an area tend to occur later than the time of maximum insolation

  37. Minimums and Maximums of Temperature Yearly • Highest surface temperature in NYS: Late July – Early August • Day of maximum duration and intensity of insolation occurs on June 21 • Why the delay? Earth is still receiving more energy than it is losing • Heat surplus

  38. Minimums and Maximums of Temperature Yearly • Lowest surface temperature in NYS: Late January – Early February • Day of minimum duration and intensity of insolation occurs on Dec 21 • Why the delay? Earth is still receiving less energy than it is radiating • Heat deficit

  39. Minimums and Maximums of Temperature

  40. Minimums and Maximums of Temperature Daily • Solar noon is the time when the sun is the highest in the sky for the day • Mid-afternoon (~3pm) tends to be the time period for the highest temperatures for the day • Even though the sun is getting lower in the sky, the earth is still receiving more energy than it is radiating (heat surplus)

  41. Minimums and Maximums of Temperature • When would you expect the lowest temperatures for the day to occur? Explain.

  42. Minimums and Maximums of Temperature

  43. Heat Budget and Climate Change

  44. Heat budget • Heat budget - the result of the balance between heat absorbed and heat lost • The temperature of an object • For Earth - the balance between the energy gained from the sun and lost through radiation from Earth to space • Earth’s average temperature

  45. Climate Change • If there is a change in the heat budget - or average temperatures of the earth - global climate change can occur • In the past the climate of the earth has changed dramatically due to changes in the Earth heat budget

  46. Examples of Climate Change • Ice Ages/Long Warm Periods • Ice Ages – Large glaciers covered large parts of Earth’s surface during cold periods • Most recent ice age - 10,500 years ago • During cold periods the average sea-level is lower and coastlines are further out than their present location • Much of the water is in the glaciers • During warm periods coastlines flood and sea levels rise

  47. Examples of Climate Change • El Niño/La Niña • El Niño occurs when a shift in wind patterns across the Pacific push warm waters toward the west coast of South America • Causes major changes in weather patterns all over the world • Can cause droughts, flooding, tornadoes • El Niño events usually occur every 5-10 years

  48. Examples of Climate Change • El Niño/La Niña • La Niña occurs when very cold waters occur off the coast of South America • Also cause changes in global weather patterns

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