Chapter 3: Introduction to the Atmosphere

1. Chapter 3: Introduction to the Atmosphere Image courtesy of cimss.ssec.wisc.edu

2. Importance of Earth’s Atmosphere • Provides oxygen • Weather (short-term) & Climate (long-term) • Protection from UV radiation & meteors • Temperature Control • Water (hydrologic cycle)

3. Size of Earth’s Atmosphere • Atmosphere uniformly surrounds Earth • Held down by Earth’s gravity • Extends up to 10,000 km from the surface • More than 50% of the total mass is below 6 km Figure 3-2

4. Composition of the Atmosphere • Two primary gas types • Permanent • Oxygen & Nitrogen • Neither plays a major role in atmospheric processes • Variable • Water Vapor • Carbon Dioxide • Ozone • Play significant role in weather & climate • Permanent gases make up over 95% of total atmosphere

5. Water Vapor in the Atmosphere • Amount of water vapor in the atmosphere varies from 0-4% • Water vapor transports heat & regulates temperature

6. Carbon Dioxide in the Atmosphere • Carbon dioxide also regulates temperature • Amount of atmospheric CO2 is about 0.039%, but it’s rising • Greenhouse Effect

7. Composition of the Atmosphere • Particulates • Non-gaseous particles which exist in the atmosphere • Human-induced & natural types • Some are hygroscopic • Some reflect or absorb sunlight Figure 3-4

8. Vertical Structure of the Atmosphere • Thermal Layers (temp. alternates from one layer to the next) • “Sphere” = entire layer • “Pause” = upper boundary of a layer • Troposphere—lowest layer; weather occurs here; tropopause • Thickest at Equator & thinnest at Poles due to the Earth’s rotation & convection • Stratosphere—stagnant air; ozone layer; stratopause • Mesosphere—middle of atmosphere; meteors burn up; mesopause • Thermosphere—“heat” • Exosphere—transitions into space Figure 3-5

9. Vertical Structure of the Atmosphere • Air Pressure • “Weight” of the air • Decreases with height at non-constant rate • Low-levels compressed by air above, so surface pressure is higher • 90% of atmosphere is in lowest 16 km Figures 3-7 & 3-8

10. Measuring Atmospheric Pressure

11. Vertical Structure of the Atmosphere Figure 3-9 • Composition • Homosphere—uniformly mixed • Heterosphere—layered • Ozonophere—AKA ozone layer; high concentration of O3 • Ionsophere—electrically charged ions; source of auroras

12. Depletion of the Ozone Layer • Natural Ozone (O3) • Naturally produced by UV radiation to shield us from UV radiation • Introduction of impurities into the atmosphere at rapid pace • Received international attention in recent years Figure 3-11

13. Depletion of the Ozone Layer • Chemistry of Ozone Layer depletion • Reduction/destruction of ozone by CFCs • The “Hole” in the Ozone layer • Mainly affects polar regions Figure 3-12 Figure 3-13

14. Human-Induced Atmospheric Change Figure 3-15: Santiago, Chile Smog • Primary vs. secondary pollutants • Primary pollutants • Particulates • Carbon monoxide • Nitrogen compounds • Sulfur compounds • Secondary pollutants • Photochemical smog • Ozone Los Angeles, CA Smog

15. Weather and Climate • Weather—short-term atmospheric conditions for a specific area • Meteorology • Climate—aggregate long-term weather conditions • Climatology • Weather vs. climate

16. Weather & Climate: Latitude • Latitudeis the most important/significant control of weather and climate • Heat received across Earth’s surface from sunlight is a function of latitude Figure 3-16

17. Weather & Climate: Distribution of Land & Water • Distinction between maritime & continental climates • Dallas, TX, & San Diego, CA, have very different climates • Maritime climates = humidContinental climates = dry • N. (Land) Hemisphere vs. S. (Water) Hemisphere Figure 4-24

18. Weather & Climate: General Circulation of the Atmopshere & Oceans • General circulation of the atmosphere • Semipermanent wind pattern on Earth • Varies with latitude • General circulation of the oceans • Oceanic broad-scale semi-permanent motions • Help transfer heat Figure 3-17

19. Weather & Climate: Altitude & Topography • Altitude • All 4 controls of weather and climate affected by altitude • Topographic barriers • Can drastically alter climate due to orographic change in wind patterns • Windward side vs. Leeward side Figure 3-20

20. Weather & Climate: Storms • Storms • Control weather & climate through atmospheric modification • Some storms are prominent enough to affect climate Figure 3-21

21. Weather and Climate • Coriolis effect • Rotation of Earth modifies path of forward motion of free-moving objects over great distances • Curves to the right in the N Hemisphere • Curves to the left in the S Hemisphere • Deflection greatest at the poles; zero at the equator • Proportional to speed of the object • Only influences direction of an object; noinfluence on speed of an object

22. Weather and Climate • Coriolis effect Figure 3-22

23. Summary • Earth’s atmosphere is a shallow “ocean” of air that uniformly surrounds the Earth • The atmosphere consists of many permanent and variable gases • The gas with the highest concentration in Earth’s atmosphere is nitrogen (78%) • The atmosphere has various vertical structures that describe it • Five main spheres make up the thermal atmosphere • The homosphere and heterosphere describe the gas composition of the atmosphere at different heights • Most auroral activity occurs in the ionosphere • Human activity has modified the atmospheric composition through pollution and ozone depletion • Weather and climate, while related, involve atmospheric conditions on different time scales • Many controls exist that modify the four primary weather elements • The Coriolis effect is an apparent force that exists due to the rotation of Earth