topic 6: insolation and the seasons

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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 - PowerPoint PPT Presentation

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TOPIC 6: INSOLATION AND THE SEASONSSolar Radiation and InsolationInsolation Incoming solar radiation

Components of Insolation (by EM type)Infrared 48% Visible Light 44%Ultraviolet 7%Effects of Earths Atmosphere on Insolation

Absorption of EMUV rays are absorbed by the ozone layer.However, there is a hole in the ozone which allows UV to hit Earth and can cause cancer.

Infrared radiation absorbed by carbon dioxide, water vapor and methaneThese are called greenhouse gasses

Effects of Earths Atmosphere on Insolation

Reflection and ScatteringConditions that cause HIGH REFLECTION of insolationClouds = lots of visible and IR reflectedAerosols small suspended particles in the atmosphere (dust, ice, water, ash) Lots of aerosols cause lots of scattering of insolationLow transparency of atmosphereBalance of Energy from Insolation Half of the insolation hitting Earths atmosphere will reach Earths 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

Balance of Energy from InsolationThe amount of heat absorbed, over time, will EQUAL amount of heat radiated so that Earths surface temperature will tend to balanceDynamic equilibrium

Factors Affecting Absorption and Reflection of InsolationAngle of Incidence the angle at which the suns energy hits the surface of the earthAngle varies with latitude, time of day and seasonThe higher the angle of incidence the more energy is absorbed

Factors Affecting Absorption and Reflection of InsolationCharacteristics of Earths SurfaceMore energy is absorbed if Earths surface is dark and roughFactors Affecting Absorption and Reflection of InsolationChange of State (of water) and TranspirationIn general, when water is changing phase solid liquid gas energy is absorbedIf energy needs to be absorbed to change phase it isnt available to raise temperature of Earths surfaceHeating Land and WaterLand heats faster over time than water because land has a lower specific heat

Insolation can penetrate deeper into water.

Heating water is done by convection so water layers mix.

Greenhouse EffectWorks on the idea that re-radiated energy is at a longer wavelength than incoming insolationGreenhouse gasses (CO2, H2O, CH4) allow short wave EM in, but absorb longer wave EM that is re-radiated by EarthThe Greenhouse Effect keeps Earths temperature warm enough to support life

Greenhouse EffectGlobal Warming - an increase in the Earths average temperatureDue to an increase in CO2 and methane which traps re-radiated waves and raises Earths surface temperatureCauses include burning of fossil fuels and deforestation

Variation of InsolationInsolation varies 2 waysIntensityDurationIntensity of InsolationIntensity of insolation - amount of solar energy received by an area over a certain amount of timeIntensity of insolation received by an area depends on the angle of incidenceAngle of IncidenceIntensity of insolation is the greatest when the suns rays hit the surface of the earth at 90oAngle of IncidenceAt angles less than 90o the insolation gets spread out over a larger areaThe same amount of energy is spread out over a bigger area, so each part of that area receives less energyAngle of Incidence

Angle of IncidenceAs the angle of incidence increases, the intensity of insolation increasesAngle of IncidenceIntensity of InsolationIntensity of InsolationThe suns rays are parallel to each other as they approach EarthIf 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 earths surface varies

Angle of IncidenceAs the latitude increases, the angle of incidence decreasesLatitudeAngle of IncidenceAngle of IncidenceAs the latitude increases, the intensity of insolation decreasesLatitudeIntensity of InsolationIntensity of Insolation

Angle of IncidenceOnly one location on earth receives the suns energy at 90o at a given timeThe location varies throughout the yearDateLocationMarch 21June 21September 23December 21Intensity of InsolationThe angle of incidence varies for a given location throughout the yearAngle is the highest on the day that the sun is highest in the skyMost intense insolation = summer solstice= June 21 for New YorkAngle is lowest on the day that the sun is the lowest in the skyLeast intense insolation = winter solstice = Dec. 21 for New YorkIntensity of Insolation

June 21Summer Solstice in NYSDec 21Winter Solstice in NYSDec 21Winter Solstice in NYSIntensity of InsolationThe angle of incidence varies for a given location during the dayAngle is the highest a solar noonMost intense insolationIntensity of Insolation

Duration of InsolationDuration of insolation - the length of time between sunrise and sunsetDuration of insolation varies for a given location throughout the yearLongest day = longest duration of insolationJune 21 in New YorkShortest day = shortest duration of insolationDecember 21 in New YorkDuration of Insolation

Suns path in summer in NYSJune 21Suns path in winter in NYSDec 21Duration of InsolationDuration of insolation is usually different at different locations on EarthJune 21 is the longest day in the Northern Hemisphere, shortest day in the Southern HemisphereDuration of InsolationDuration of insolation is 12 hours all over the earth on the equinoxesMarch 21, September 23Duration of Insolation

Insolation and Surface TemperaturesThe intensity of insolation and the duration of insolation together determine the surface temperatures for an areaThe more intense the insolation, the more energy an area receives, the higher the temperatureThe longer insolation is received at an area, the more energy absorbed, the higher the temperatureInsolation and Surface Temperatures

Insolation and Surface TemperaturesThe Earth heats up when it absorbs more energy than it radiatesWhen the energy gained by an area is GREATER than the energy it radiates, its temperatures will riseWhen the energy gained by an area is LESS than the energy it radiates, its temperatures will fallMinimums and Maximums of TemperatureThe highest temperatures of the year for an area tend to occur later than the time of maximum insolationMinimums and Maximums of TemperatureYearlyHighest surface temperature in NYS: Late July Early AugustDay of maximum duration and intensity of insolation occurs on June 21Why the delay? Earth is still receiving more energy than it is losingHeat surplusMinimums and Maximums of TemperatureYearlyLowest surface temperature in NYS: Late January Early FebruaryDay of minimum duration and intensity of insolation occurs on Dec 21Why the delay? Earth is still receiving less energy than it is radiatingHeat deficitMinimums and Maximums of Temperature

Minimums and Maximums of TemperatureDailySolar noon is the time when the sun is the highest in the sky for the dayMid-afternoon (~3pm) tends to be the time period for the highest temperatures for the dayEven though the sun is getting lower in the sky, the earth is still receiving more energy than it is radiating (heat surplus)Minimums and Maximums of TemperatureWhen would you expect the lowest temperatures for the day to occur? Explain.Minimums and Maximums of Temperature

Heat Budget and Climate ChangeHeat budgetHeat budget - the result of the balance between heat absorbed and heat lostThe temperature of an objectFor Earth - the balance between the energy gained from the sun and lost through radiation from Earth to spaceEarths average temperatureClimate ChangeIf there is a change in the heat budget - or average temperatures of the earth - global climate change can occurIn the past the climate of the earth has changed dramatically due to changes in the Earth heat budgetExamples of Climate ChangeIce Ages/Long Warm PeriodsIce Ages Large glaciers covered large parts of Earths surface during cold periodsMost recent ice age - 10,500 years agoDuring cold periods the average sea-level is lower and coastlines are further out than their present locationMuch of the water is in the glaciersDuring warm periods coastlines flood and sea levels rise

Examples of Climate ChangeEl Nio/La NiaEl Nio occurs when a shift in wind patterns across the Pacific push warm waters toward the west coast of South AmericaCauses major changes in weather patterns all over the worldCan cause droughts, flooding, tornadoesEl Nio events usually occur every 5-10 years

Examples of Climate ChangeEl Nio/La NiaLa Nia occurs when very cold waters occur off the coast of South America Also cause changes in global weather patterns

Examples of Climate ChangeGlobal WarmingThe average temperature of the earth is risingCauses of Heat Budget ShiftsSolar Energy ChangesSunspots are dark areas on the suns surfaceWhen there are a lot of sunspots, the sun emits more electromagnetic energy = more insolation

Causes of Heat Budget ShiftsChanges in Shape of Earths Orbit and TiltThere are changes that occur in the eccentricity of Earths orbit and the tilt of Earths axisMay cause cooler summers and warmer wintersPossible cause of ice agesCauses of Heat Budget ShiftsChanges in Earths AxisEarth rotates on an axis tilted at 23 1/2 degreesSince earth is not a perfect sphere, it bobbles like a topNorth pole not always pointed at the same placeCalled precessionCauses of Heat Budget ShiftsChanges in Earths Axis

Causes of Heat Budget ShiftsChanges in Earths Axis

Causes of Heat Budget ShiftsChanges in Earths TiltEarths tilt on its axis changes through timeVaries between 22o and 24oCurrently at 23oWhen the tilt is greater summers are warmer, winters are colderCauses of Heat Budget ShiftsVolcanic EruptionsVolcanic eruptions cause temperature of Earth to co

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