Lecture 2 Atmospheric Constituents and Vertical Structure

1. Lecture 2Atmospheric Constituentsand Vertical Structure

2. Chapter 1 – Introduction to the Atmosphere • Weather • The state of the atmosphere at any given time. • Climate • A description of aggregate weather conditions. • The sum of all statistical weather information that helps describe a place or region. “Climate is what you expect, but weather is what you get”

3. The Atmosphere The Layers of the Atmosphere • VERY THIN • 99% is within 19 miles (30 km) of the surface. • Provides the airwe breath • Provides protection from damaging UV radiation from the Sun NOT TO SCALE!!!! http://www.theozonehole.com/atmosphere.htm

4. Modern Atmospheric Composition • 78% Nitrogen (N) • 21% Oxygen (O) • 1% Argon (Ar) • Other Gases and Constituents • Carbon Dioxide (CO2) – from respiration, combustion, GHG • Methane (CH4) – cows, wetlands, rice patties, low oxygen environments, GHG • Ozone (O3) – in both the stratosphere (good) and troposphere (bad) • Water (H2O) – 0-5% variable over the surface of the earth • Hydrogen (H2) • Helium (He) • Carbon Monoxide (CO) • Ammonia (NH3) • Nitrogen Oxide (NO) • Nitrous Oxide (N2O) • Sulfur Dioxide (SO2) • Nitrogen Dioxide (NO2) • Particles – Aerosols, dust, smoke

5. Atmospheric Composition • Where did all the Nitrogen come from? • The answer lies mostly in three facts: • nitrogen isvolatilein most of its forms • it isunreactivewith materials that make up the solid earth • it isvery stablein the presence of solar radiation. Nitrogen Cycle http://www.chemicool.com/elements/nitrogen.html

6. Atmospheric Composition Nitrogen Cycle • Where did all the Nitrogen come from? • Over geological time, it hasbuilt upin the atmosphere to a much greater extent than oxygen • It is an important component of life on earth (Nitrogen Cycle) http://www.chemicool.com/elements/nitrogen.html

7. Atmospheric Composition • Where does the oxygen come from? • The primary way in which the Earth generates oxygen is through photoshynthesis. • Photosynthesisaccounts for 98% of the world's atmospheric oxygen • Thebreakup of water moleculesby ultraviolet radiation composes the other 1-2%.

8. Atmospheric Composition • Why is Argon Third? • Argon is formed byradioactive decay • Released slowly into the atmosphere throughvolcanic activity. • It is aninert (and nonradioactive) gas and does not react chemically, so it gradually accumulates in the atmosphere. • Fun Fact: Used in Neon Lights!

9. Atmospheric Composition • Carbon dioxide • News worthy  Global Climate Change • CO2 is an efficient absorber of energy emitted by the sun! • Present in tiny amounts • ~0.0387% or 387 ppm

10. Atmospheric Composition • Carbon dioxide • Amount of CO2 is relatively constant over the earth • Records a steady increase since the 1960s…. • Keeling Curve We’ll talk more about later • These measurements made in HAWAII on top of Mauna Loa

11. Atmospheric Composition • Variable Components • Water Vapor • Varies from 0-4% by volume • Clouds and precipitation • Heats the atmosphere like CO2 • Releases or absorbs energy when it changes states (gas-liquid-solid) • Aerosols • Tiny solid and liquid particles • Dust, pollution, sea salt, ash, smoke, biogenic particles • Ozone • NEXT SLIDE!

12. Atmospheric Composition • Ozone (O3) • Three Oxygen Molecules! • Concentrated high above the surface (in the stratosphere) • Protects us from UV rays from the sun (what gives us sun burns)

13. Atmospheric Composition • Ozone Hole • We’ll go into detail later… • Predominantly found in theAntarctic,though one happened in the Arctic in 2011. • Montreal Protocol– What happens when the scientists and politicians of the world come together.SUCCESS!!!

14. Evolution of the Atmosphere • First atmosphere: • Hydrogen (H) and Helium (He) • 4.6 billion years ago • Swept away by solar winds, escaping the earth’s hot surface. • Primeval Phase: • An atmosphere unfamiliar to us, next few slides • Modern Phase: • What we live in now

15. Primeval Atmosphere • The principle source of atmospheric gases wasOUTGASSING • The release of gases from rock through volcanic eruptions and impact of meteorites • Primeval Atmosphere was mostly • CO2, N2, H2O, little CH4, NH3 (ammonia), SO2, HCl. • Radioactive decay of an isotope of potassium added argon. • Free Oxygen (O or O2) was absent!!!

16. Primeval Atmosphere • After 4 billion years, the Earth’s surface cooled • Water vapor to condense into clouds and rain • Oceans and rivers formed • CO2 dissolves in water • rain, and oceans, “washed out” some of the CO2… cooling the planet further. • After life emerged, primarily photosynthetic bacteria emerged • O2 began building up

17. Extent of the Atmosphere • No clear boundaryat the upper atmosphere • Rapidlythins as altitude increases (density decreases) • Halfthe atmosphere lies below ~5.6 km (3.5 miles) • Pressure decreases with Height. • Rate ofpressure decrease is not constant(red line) • Air is HIGHLY compressible MEMORIZE this PLOT!

18. Extent of the Atmosphere • Standard Atmospheric Pressure: • 1013.25 mb • 1013.25 hPa • 29.92 in. Hg. • Near surface air is more dense. • Decreases rapidly at first then more slowly MEMORIZE this PLOT!

19. Thermal Structure of the Atmosphere IMPORTANT NOTE: You WILL need to be able to DRAW this figure from MEMORY on a quiz or exam! It is VERY important!

20. Troposphere • Warmed by the surface of the Earth!!!! • Where “Weather” happens • Due to vertical and horizontal mixing of air • Temperature DECREASES with height • Environmental lapse rate • 6.5 deg K per km • 3.6 deg F per 100 ft • Highly variable • Decreases until ~12 km • TROPOPAUSE!

21. Stratosphere • TemperatureINCREASESwith height • Due to the presence ofOZONE, which heats the layer • Ozone absorbs solar radiation • Maximum from 15-30 km • We study this layer with • Weather balloons • High altitude aircraft • Satellites

22. Mesosphere • COLDESTtemperatures in the atmosphere are observed here • Not heated by the Earth or Ozone! • Pressure is very low • Is the least studied region

23. Thermosphere • Begins after the Mesosphere and has no well defined upper limit • Temperature begins toINCREASEwith height again! • Temperatureis defined as: • Average speed at which molecules move • Gases here move FAST in thermosphere • Even though there are few of them… • What if an astronaut exposed his hand? • It would not feel hot, not enough particles!

24. Key Information 1 • Know the main components of the atmosphere, their percentages and how they reached current levels • N2 (78%), O2 (21%), Argon (1%) • Identify other components of interest: • CO2, Ozone, Water Vapor, Particles, etc. • Describe the primeval atmosphere and how the current atmosphere evolved • Identify processes involved (i.e. Outgassing and Photosynthesis)

25. Key Information 2 • Know altitudes & pressure values • Know at what altitude below which 50% of the atmosphere is located • 5.5 km • Know why the pressure and density curves look the way they do: • Gravity & Compressibility of air • Know Standard Pressure Values • 1013.25 mb • 29.92 in. Hg • Be able to draw how atmospheric pressure changes with height

26. Key Information 3 • Know altitudes and temperature values • Identify each of the layers and their boundaries • Troposphere, tropopause, stratosphere, stratopause, mesosphere, mesopause, thermospehre & ionosphere • Be able to describe how and why temperature changes in each layer. • Be able to draw how atmospheric Temperature changes with height!