SOAR 2007

1. SOAR 2007 Earth’s Atmosphere and Wind

2. Course Outline • Course Outline • Atmospheric structure, pressure & wind • Oceanic Circulation • Energy transfer & circulation • Past Climates • Global Climate Change

3. Origin of Planets • Coalescence of matter in circumsolar cloud • Many Craters • Collisions  heat! • Molten interior • Interior layered • Denser materials sink to center • Core mostly Iron (Fe) & Nickle (Ni) • Crust mostly rocky (CaCO3, SiO2, etc)

4. Planetary Atmospheres • Form from • Gases from planet’s interior (volcanoes) • Gases from impacts (planets) • Terrestrial Planets • Mercury – none • Venus CO2 with H2SO4 clouds • Mars – CO2 with H2O clouds • Earth – N2 with O2 • Jupiter & Saturn – H with NH3 clouds • Galilean moons – traces • Titan – N2 with CH4 • Uranus & Neptune – H with CH4 clouds

5. Planetary Atmospheres avg • Escape Velocity • Molecular Speed & Temp • or avg

6. Planetary Atmospheres • Presence & size due to combination of • Temperature = Distance from Sol • Size of world = escape velocity • Large worlds • Keep atmospheres even close to Sol • Small worlds • Only have atmospheres far from Sol • Composition due to • Size of world • Large worlds keep small molecules (H) • Small worlds keep large molecules (N2, O2, CO2)

7. Inner Planets • Mercury • Small, hot  no atmosphere stays • Venus • Large, hot  thick atmosphere • NO WATER H2O  H2 + O that binds with C, S, etc • CO2 + H2S04 Clouds • Run-away greenhouse effect • Mars • Small, cool  thin atmosphere & thinning • Evidence of ancient oceans but water now present only as solid and gas • CO2 + H2O Clouds, fogs

8. Mars & Venus • Both primarily CO2 but very different! Mars 95.3% CO2 Venus 96.5% CO2 250K – 273K = -23ºC = -10ºF 750K – 273K = 477ºC = 890ºF

9. Venus: Greenhouse gone wild!

10. Interaction with Sunlight • Sky is blue because blue scatters, red doesn’t

11. Earth • Complex atmospheric evolution • Primordial Atmosphere Lost to space • H & He very light molecules, escape easily • Initially like Venus & Mars: mostly CO2 • THEN • Water condensed into oceans • Oceans absorbed CO2 • Locked it into rocks (CaCO3 = limestone) • Life flourished in oceans • Released free oxygen • Sedimentary rocks turned red • Ozone layer formed

12. Evolution of Earth’s Atmosphere Oxygen content created, maintained by life.

13. Atmospheric Structure • Layers (from surface) due to • Density (Pressure) • Radiation Environment • Temperature

14. Atmospheric Structure • Layers (from surface) • Troposphere – sphere of weather • Stratosphere – sphere of ozone (O3) • Mesosphere • Ionosphere – sphere of ions

15. Atmospheric Structure • Layers By Function • Ozonosphere (O3 layer) • Upper portion of Stratosphere • Absorbs UV (0.1-0.3 nm), radiates IR • Warmest layer in atmosphere • Harmed by CFC’s • Cl + 2O3 Cl + 3O2 … and Cl is free to kill again! Ozone constantly created & destroyed by UV, CFC’s increase destruction Hole in the ozone layer over Antarctica

16. Atmospheric Structure • Layers By Function • Ionosphere • Thermosphere & Mesosphere • Ionized particles (UV + atoms  ions + e- + energy • Absorbs -rays, x-rays, UV, cosmic rays • Reflects AM radio waves

17. Importance of Wind Force Newtons = = = = P Pascal Pa ( ) 2 Area meter • Arises due to differences in pressure • Distributes • heat • moisture • dust • pollutants • microscopic life

18. Air Pressure • Pressure is force/area = weight of air column • 1 in2 column • weight = 14.7 lb • 1 m2 column • weight = 10 tonnes • 1 tonne = 1000 kg = 2204 lb • Why doesn’t the air pressure crush you when you lie down?

19. Air Pressure • Standard Atmosphere • 760 mm Hg • 29.92 in Hg • 33.9 ft. H2O • 1013 millibars (mb) • 1013 hPa hectopascals Weight of column of Hg Weight of column of air Weight of Hg = Weight of Air Hg(tube area)(column height) = (air presure)(bowl area)

20. Air Pressure H = - log P 5 10 15500 • Varies with • altitude (in Pa, H in m) • air motion • rising air = low pressure • subsiding air = high pressure • moving air is at lower pressure than still (or slower moving air … wind pulls curtains against window screen & airplane wings up!

21. Air Motion • Updrafts – upward motion of air • Downdrafts – downward motion of air • Wind • Horizontal motion of air across Earth’s surface (advection) • Measured by anemometers • 1 knot = 1 nautical mile/hour = (1 minute of latitude)/hour = 1.852 kph = 1.15 mph • Speed and Direction recorded

22. Driving Forces • Gravitational Force • Earth’s gravity holds atmosphere • Pressure Gradient force • isobar = line of constant pressure • Pressure Gradient force acts perpendicular

23. Importance of Wind Only a difference in pressure makes air move.

24. Driving Forces Pressure Gradient force Indicated by density of isobars

25. Driving Forces Pressure Gradient force Indicated by density of isobars 18 hPa across ~400 km North America & Greenland, February 6, 18Z (1 pm EST)

26. Driving forces • Pressure Gradient force • from high pressure to low pressure

27. Driving Forces force r r µ F v velocity • Coriolis Force • Acts ONLY ON MOVING objects • proportional to velocity ( ) • perpendicular to velocity • acts over large distances • Does not determine direction water spins down a drain! The rolling ball follows a straight path seen from above, a curved path seen from the rotating reference frame (riding on the merry-go-round).

28. Coriolis Force Projectile carries small speed, falls behind high speed equator. Different latitudes “orbit” axis at different speeds.

29. Coriolis Force • All moving objects are deflected • to their right in northern hemisphere • to their left in southern hemisphere Coriolis force deflects velocity no matter what the original direction of the velocity!

30. Coriolis Force: All moving objects are deflected to their right in northern hemisphere to their left in southern hemisphere

31. Coriolis Force Northern Hemisphere Moving objects deflected to their own right. Southern Hemisphere Moving objects deflected to their own left. Tropical Cyclone Olyvia L L Hurricane Isabel Storms rotate counterclockwise Storms rotate clockwise

32. Cyclones & Anticyclones • Cyclone – circulation around low pressure • CCW in northern hemisphere • CW in southern hemispere • Anticyclone – circ. around high pressure • CW in northern hemisphere • CCW in southern hemisphere http://www.usatoday.com/weather/tg/whighlow/whighlow.htm

33. Driving Forces • Friction • Friction with ground slows wind • Extends upward ~ 500 m • Varies with surface, time Surface air slows air aloft Friction with ground slows wind

34. Geostrophic Winds wind along isobar • Pressure Gradient Force • creates wind ⊥ to isobars • Coriolis Force • deflects motion to right in N. hemisphere ⇒ deflects Coriolis force! Forces Balance Isobars Wind deflects due to Coriolis force Pressure Gradient force Coriolis force Coriolis force acts perpendicular to new wind direction wind velocity

35. Geostrophic Winds • Pressure Gradient Force • creates wind ⊥ to isobars • Coriolis Force • deflects motion • to its right in N. hemisphere • to its left in S. hemisphere • aligns wind with isobars

36. Surface Winds: Not Geostrophic • Friction slows winds at surface • Reduces Coriolis force • Pressure Gradient force dominates

37. Convection Cells • Sunlight heats land, water, air • Land warms, heats air • Air circulates • Convection cells • warms -> expands -> rises • cools -> contracts -> sinks • Water circulates • Currents driven by wind & Earth rotation • Water temperature increases SLOWLY • Large energy change needed for small temp. change Heat

38. Convection Cells • Hot surface heats air • Air expands, • becomes less dense than surroundings • rises, spreads out at top • Air aloft cools, • becomes more dense than surroundings • sinks, spreads out on surface Heat

39. Atmospheric Circulaton • Rising Air • Cools • Water vapor condenses • (usually) results in clouds • Lowers surface pressure

40. Atmospheric Circulaton • Falling Air • Warms • DRY (lost mosture rising) • Increases surface pressure

41. Atmospheric Circulation Heat Maximum Insolation • Sunlight heats ground • Ground heats air , drives convection from subsolar latitude Subsolar latitude is 0º on the equinoxes Subsolar latitude is 23.5º N/S on the solstices

42. Atmospheric Circulaton Driven by heating near equator Air rises from subsolar latitude, clouds form & precipitate, air aloft moves N & S, cools, dries & sinks at about 30º N & S Dry air falling  Arid Moist air rising  humid Air spreads N & S on surface Air aloft cools until it sinks

43. Atmospheric Circulaton Driven by cooling near poles Cold, dry air falling  Arid Surface flows converge, rise Air warms and moistens along surface Dry air falling  Arid Air from aloft sinks near poles, moves N & S along surface Moist air rising  humid

44. Moist air rising  stormy Polar Front Dry air falling  Arid Deserts Moist air rising  stormy Rainforests Deserts Dry air falling  Arid Polar Front Hadley Cells

45. Pressure Zones InterTropical Convergence Zone Polar Front Rising Air: Low Pressure ITCZ Polar Front

46. Pressure Zones Polar High STHPC Falling Air: High Pressure STHPC Polar High

47. Pressure Zones Polar High Polar Front Pressure Zones:air motion is vertical so there is little wind! STHPC ITCZ STHPC Polar Front Polar High

48. Wind Zones Winds:Falling air spreads North & South along surface. But the winds don’t go straight!

49. Wind Zones Easterlies Polar Front Westerlies Horse Latitudes NE Trades Doldrums SE Trades Horse Latitudes Westerlies Polar Front Easterlies Winds named for direction they are from Windless zones names vary

50. General Atmospheric Circulation Polar Front Horse Latitudes Doldrums • Cross sectional view ITCZ STHPC Polar High Easterly Trades Polar Easterlies Westerlies