15 Lecture Material for Introduction of Environmental Physics Class 12 EE Batch1. Sound and Light2. Radiation Understanding3. Global Warming4. Terrestrial Environment5. Extra-Terrestrial Environment6. Natural and Man made radiation7. Universe understanding8. Understanding water9. Cloud formation10. Climate11. Climate change
Radiation Understanding1. EATRH’S ATMOSPHERE2. STRUCTURE3. SUN’S ELECTROMAGNETIC SPECTRUM4. Energy from the Sun5. Atmospheric Greenhouse Effects
Radiation and Earth’s Atmosphere• The earth’s global average surface temperature in present climate is 15C (59F). Without the atmosphere, it would be -18C (-0.4F),• About 33C or 59.4F colder! Atmosphere is the most important component of the earth’s climate.• Radiation vs. other heat sources:• Total energy enter the earth’s atmosphere: 174 petawatts or 174X1015 Watts• Solar: 99.978%, Geothermal: 0.013%, waste and fossil fuel: 0.007%, tidal: 0.002%
Earth’s Atmosphere1. What is it? A thin gaseous envelope around the planet. Blue sky!2. Composition Today’s atmosphere: nitrogen (78%), oxygen (21%), other (1%) – trace gases! Nitrogen, oxygen, argon, water vapor, carbon dioxide, methane, and most other gases are invisible. Clouds are not gas, but condensed vapor in the form of liquid droplets or ice particles. Ground based smog, which is visible, contains reactants of nitrogen and ozone.3. Structure Four layers: Troposphere (overturning) From surface to 8-18 km Stratosphere (stratified) From troposphere top to 50 km Mesosphere Thermosphere
The Structure of Earth’s Atmosphere1. Four layers defined by temperature Troposphere: T decreases with elevation Stratosphere: T increases with elevation Mesosphere: T decreases with elevation Thermosphere: T increases with elevation2. Importance to climate and climate change Troposphere: 80% of Earth’s gases Most of Earth’s weather happens Most of the measurements Stratosphere: 19.9% of Earth’s gases Ozone layer: Blocking Sun’s ultraviolet radiation
Energy from the Sun1. Characteristics Travels through space (vacuum) in a speed of light In the form of waves: Electromagnetic waves In stream of particles (Photons) Releases heat when absorbed2. Electromagnetic spectrum From short wavelength, high energy, gamma rays to long wavelength, low energy, radio waves3. Importance to climate andclimate change Primary driving force of Earth’s climate engine Ultraviolet, Visible, Infrared
Sun’s Electromagnetic SpectrumSolar radiation has peak intensities in the shorterwavelengths, dominant in the region we know as visible, thusshortwave radiation
Longwave & Shortwave Radiation The hot sun radiates at shorter wavelengths that carry more energy, and the fraction absorbed by the cooler earth is then re-radiated at longer wavelengths.
Atmospheric Greenhouse Effects T= 15°C (59°F)Surface Temperature With theAtmosphere T= –18°C (0°F) Surface Temperature Without the Atmosphere Greenhouse effects make Earth’s surface warmer!
Greenhouse Gases What are they? Water vapor (H2O) Carbon dioxide (CO2) Methane (CH4) Ozone (O3) Chlorofluorocarbons Nitrous oxide (N2O) (CFC’s) Water vapor accounts for 60% of the atmospheric greenhouse effect, CO2 26%, and the remaining greenhouse gases 14%. CO2 contributes most (55-60%) to the anthropogenic greenhouse effect, and methane is a distant second (16%). CFCs cause the strongest greenhouse warming on a molecule-for-molecule basis.
NitrousAtmospheric Absorption Oxide MethaneSolar radiation passesrather freely throughEarths atmosphere. Ozone AbsorptionEarth emits longwave Water Vapor (100%)energy, which eitherleaks through a narrowwindow or Carbon Dioxideis absorbed by UVgreenhouse gases and IRradiated back to Earth. Total Atmo Wavelength
Solar Intensity and LatitudeSolar intensity, defined as the energy per area, is different atdifferent latitude.A sunlight beam that strikes at an angle is spread across a greatersurface area, and is a less intense heat source than a beamimpinging directly.
Unequal Radiation on a Sphere Insolation is stronger in the tropics (low latitudes) than in in the polar regions (high latitudes).
What controls the elevation of the Sun above the horizon? Earth’s Tilt Primarily Determines Season
Earths Annual Energy BalanceThe balance isachieved locally Incoming Solarat only two lines Radiationof latitude.A global balance Outgoing Longwaveis maintained by Radiationexcess heat fromthe equatorialregiontransferringtoward thepoles. Unequal heating of tropics and poles
The Global Energy Budget: Driver of Atmospheric Motion A balance exists between the incoming solar and outgoing longwave energy averaged over the globe and the year However, the tilt of theSURPLUS DEFICIT Earth means this balance is not maintained for each latitude
Questions:• What is the current global mean surface temperature?• Why it is 33C or 59F warmer than it would be without the atmosphere?• Why is climate dominated by the radiation balance of the atmosphere?• What are the main greenhouse gases in the earth’s atmosphere?• In what latitudes the earth’s gain and lost radiative energy (heat), respectively?
Questions:• What is the current global mean surface temperature? – 15C or 59F• Why it is 33C or 59F warmer than it would be without the atmosphere? – Because of greenhouse effect of the atmosphere• Why is climate dominated by the radiation balance of the atmosphere? – It contributes to 99.978% of total heat flux into the atmosphere• What are the main greenhouse gases in the earth’s atmosphere? – H2O, CO2, CH4, O3, CFCs, NO2• In what latitudes the earth’s gain and lost radiative energy (heat), respectively? – Gain heat in the tropics or 40S-40N, loss heat in high latitudes (50S-50N)
Interested in more questions? Try these questions:• Can you name one or more main causes of glacier and interglacier climate change?• What is the most important greenhouse gases for modern climate change? What is the fastest growing greenhouse gas?• Earth’s climate has been much colder and warmer than that of today. Do you know in what ways the earth’s radiation balance was altered?