1. air movement ENVS 09-26-08

2. what makes air move ? air moves from areas of high atmospheric pressure to areas of low atmospheric pressure low pressure areas – troughs high pressure areas - ridges

3. http://www.dnr.sc.gov/climate/sco/Education/wxmap/wxmap.gif

4. isobars = equal lines of pressure distance between isobars → change in pressure over distance = pressure gradient isobars close together → pressure varies rapidly → air flows rapidly form high to low pressure → strong winds

5. pressure gradient force describes how rapidly air pressure changes between two points steep gradient (isobars close together) → air moves rapidly → pressure gradient force is large shallow gradient → pressure gradient force is small

9. but… most atmospheric patterns are swirls of clouds and winds … very few straight patterns

10. The Rotating Earth → Coriolis “Force” Earth is a rotating system On earth things that move straight appear to move on curved path as earth rotates beneath swirly cloud patterns on satellite images, zone of westerlies etc.

11. Coriolis Effect does NOT determine the way your sink drains !

12. Coriolis Effect with (almost) no Math a) movement to and from the poles

13. N-S moving air: air has larger tangential velocity at equator than at pole (equator = max, pole = 0) as air moves polewards it maintains its tangential velocity since it is encountering slower moving air it “overtakes” these higher latitude air masses apparent deflection towards the right (in N – hemisphere) air moving towards the equator seems to lag lower latitude air masses → again, deflection to the right

14. from: www.bom.gov.au/info/ftweather/ page_14.shtmlwww.bom.gov.au/info/ftweather/ page_14.shtml

15. Coriolis Effect Summary: earth is a rotational system standing on earth, objects that move on straight line seem to be following curved paths (because we are rotating) Coriolis effect deflects air masses –towards right on northern hemisphere –towards left on southern hemisphere

16. Coriolis Effect - Magnitude effect is very small only affects large scale movements (Hurricanes, ocean currents etc.) it will not affect small, household scale currents

17. air currents II

18. influences on air currents pressure gradient force: air flows from areas of high pressure to areas of low pressure – the more rapid the change in pressure the stronger the flow Coriolis effect: due to rotation of the earth air masses are deflected to the right on northern hemisphere and deflected to the left on southern hemisphere resulting flow: geostrophic flow

20. Coriolis effect rotating earth → air masses are moving on curved paths across earth on northern hemisphere: deflection to the right on southern hemisphere: deflection to the left

21. coriolis effect http://www.physics.umd.edu/lecdem/services/demos/demosd5/d5-11.htm

22. Coriolis effect demonstrations stationary disk rotating disk – stationary observer rotating disk, rotating observer

23. one last time: on northern hemisphere – air is deflected to the right on southern hemisphere – air is deflected to the left due to the rotation of the earth

24. close to ground: friction between atmosphere and surface slows air down winds are stronger at high elevations

25. three influences on air movement pressure gradient force Coriolis effect friction

26. conservation of angular momentum combination of pressure gradient force and Coriolis effect cause air to spin as air is sucked into low-pressure area it spins faster and faster due to the conservation of angular momentum

27. at high altitudes friction between atmosphere and earth’s surface is negligible air currents are influenced by balance between pressure gradient force and Coriolis effect → geostrophic winds

28. development of geostrophic flow pressure gradient force gets air moving Coriolis effect deflects to right and keeps deflecting until… effects of pressure gradient and Coriolis effect cancel out → now wind flows almost parallel to isobars !

29. airflow symbols

30. http://www.atmos.washington.edu/~mcmurdie/oct96/300mb_geownd_17oct.gif

31. two ways to depict air pressure lines of equal pressure (isobars) equal pressure surfaces http://www.physicalgeography.net/fundamentals/7d.html

32. constant pressure levels are at higher elevation for high pressure areas are at lower elevation for low pressure areas

33. http://www.srh.noaa.gov/hun/stormsurveys/2008-02-06/weather/12z_500mb.jpg

37. Effect on Hurricanes: balance between Coriolis force and pressure gradient causes rotation of storm system counterclockwise in N-hemisphere clockwise in S-hemisphere

38. surface winds http://www.srh.noaa.gov/hun/stormsurveys/2008-02-06/weather/12z_500mb.jpg

39. surface winds or friction layer winds friction between atmpsphere and earth’s surface prevents air masses to reach equilibrium between coriolis effect and pressure gradient force friction layer winds blow at an angle to the isobars

40. local wind systems land and sea breezes F ö hn winds (Chinook)

41. land and sea breezes differential heating between sea and land land heats up faster and warm air rises (low pressure area over land) process reverses at night

42. F öhn winds orographic rain – air masses lose most of their moisture when they cross a mountain range on the other side the air is warm and very clear

43. for all of you who still haven’t enough…

44. Global Atmospheric Circulation ENVS 110 - 10-03-2008

48. http://en.wikipedia.org/wiki/Image:IntertropicalConvergenceZone-EO.jpg

49. Vertical air movement in the atmosphere http://en.wikipedia.org/wiki/Image:Omega-500-july-era40-1979.png

50. Seasonal Changes link

53. Polar Front Planetary frontal zone Mixing of warm and cold air  exchange of heat from subtropics to higher latitudes

54. Local effects Asian monsoon North American monsoon http://img.timeinc.net/time/photoessays/2007/india_monsoon/india_monsoon_01.jpg

55. Differential warming between continents and oceans Summer – Indian sub continents heats up Develops low-pressure zone over continent Sucks in moist air from surrounding oceans India: –Warm subtropical oceans  extremely moist oceanic air –Orographic rain on southern edge of Himalayas