1. AOSS 401, Fall 2006 Lecture 19 October 26, 2007 Richard B. Rood (Room 2525, SRB) rbrood@umich.edu 734-647-3530 Derek Posselt (Room 2517D, SRB) dposselt@umich.edu 734-936-0502

2. Class News October 26, 2007 Homework –Homework 5 posted today –Includes a programming assignment that will be posted this afternoon/evening –Focus your attention on question 1

3. Today Bring together physical concepts and preview the rest of the course Material from Chapter 6 –Middle Latitude Structure –Quasi-geostrophic theory

4. Flow over a mountain range West to East

5. What is happening with planetary vorticity? (In the (east-west, north-south) plane) Depth, H Depth, H + ΔH west east s n Depth, H - ΔH Depth, H + ΔH f is greater for deflections to north f is less for deflections to south f + ζ is less than earth’s vorticity and wants to turn north. Arrives here wanting vorticity. “Overshoots”

6. Flow over a mountain range East to West

7. What is happening with planetary vorticity? (In the (east-west, north-south) plane) Depth, H Depth, H + ΔH west east s n Depth, H - ΔH Depth, H + ΔH Flow from east planetary and relative vorticity interact together, no overshoot or undershoot.

8. Wind and geopotential 200 hPa Note: Troughs associated with mountain ranges, continents

9. Observations of the Atmosphere Vorticity –Small scale flow –Large-scale flow Large scale flow and the climate system –Heat transport –Jet streams –Development of mid-latitude cyclones

10. Vorticity on Small Scales From the southern California fires: http://video.nbc11.com/player/?id=171454 What is the cause? http://aoss-web.engin.umich.edu/class/aoss102/tools/swf/?url=class/aoss102/tools/swf/

11. Vorticity on Large Scales Remember, vorticity is caused by –Wind shear –Rotation in the flow Can we identify these on weather maps? (The following maps come from http://www.aos.wisc.edu/weather/)

12. 300 mb Wind Speed

13. Where is there positive vorticity?

14. 500 mb Vorticity

15. Thermal Wind Remember, thermal wind relates –Vertical shear of geostrophic wind –Horizontal temperature gradients Can we identify these on weather maps?

16. Where are the strongest ?

17. 850 mb Temperature

18. Convergence/Divergence Remember, vertical motion on large scales directly related to –Convergence/divergence of ageostrophic wind –Curvature in the flow Can we identify these on weather maps?

19. Where are surface lows/highs?

20. Surface Precipitation

21. 850 mb Temperature

22. Concepts Vorticity: shear and curvature –Why is curvature vorticity (as opposed to shear vorticity) usually associated with developing low pressure systems? Divergence and convergence and location of surface high and low pressure systems Thermal wind—vertical shear of the horizontal wind and horizontal temperature gradients

23. Concepts Features commonly found together –Jet stream –Upper level positive vorticity –Fronts –Midlatitude cyclones (low pressure systems) Coincidence? More on this later…

24. Large scale flow and the climate system

25. Transfer of heat north and south is an important element of the climate at the Earth’s surface. Redistribution by atmosphere, ocean, etc. SURFACE Top of Atmosphere / Edge of Space ATMOSPHERE CLOUD heat is moved to poles cool air moved towards equator This is a transfer. Both ocean and atmosphere are important! Large scale weather systems transport large quantities of thermal energy from equator toward the poles

26. Hurricanes and heat

28. Mid-latitude cyclones

29. Mid-latitude cyclones & Heat

30. Mid-latitude Cyclones & Jet Stream

31. An estimate of the January mean temperature north winter south summer tropopause stratopause mesosphere stratosphere troposphere note where the horizontal temperature gradients are large

32. An estimate of the January mean zonal wind north winter south summer note the jet streams

33. An estimate of the July mean zonal wind north summer south winter note the jet streams

34. Wind and geopotential 200 hPa Note: Variability in east-west of the wind field. Note: Troughs associated with mountain ranges, continents Note: Time variability of the wind field.

35. Waves in the atmosphere 300 mb Jet Stream Animation

36. Short summary We have strong mean zonal winds. We have latitudinal and time variability of the zonal winds –Quasi-stationary long waves. On these quasi-stationary long waves, mid-latitude cyclones form and propagate.

37. Mid-latitude cyclones What we know: –Low pressure systems –Form through spinup of low-level positive vorticity –Divergence/convergence is key This is just the beginning… –Always closely associated with fronts—why? –Sometimes develop rapidly, sometimes not at all—why?

38. The mid-latitude cyclone

39. Mid-latitude cyclones: Norwegian Cyclone Model

40. Fronts and Precipitation CloudSat Radar Norwegian Cyclone Model

41. Relationship between upper troposphere and surface note tilt with height

42. Idealized vertical cross section

43. What’s at work here?

44. Mid-latitude cyclone development

45. Mid-latitude cyclones: Norwegian Cyclone Model http://www.srh.weather.gov/jetstream/syno ptic/cyclone.htmhttp://www.srh.weather.gov/jetstream/syno ptic/cyclone.htm

46. Cold and warm advection cold warm

47. Lifting and sinking

48. Increasing the pressure gradient force

49. Relationship between upper troposphere and surface divergence over low enhances surface low // increases vorticity

50. Relationship between upper troposphere and surface vertical stretching // increases vorticity

51. Modern education at its best. http://aoss.engin.umich.edu/class/aoss102 /tools/swf/http://aoss.engin.umich.edu/class/aoss102 /tools/swf/

52. Analysis Tools We have used many of the concepts and tools that we have introduced and explored. –Observed characteristics of the atmosphere –Conservation principles –Scale analysis: Geostrophic and hydrostatic –Thermal wind –Divergence and convergence These ideas are integrated into quasi- geostrophic theory (analysis and prediction)

53. Programming Exercise Gain experience writing programs to –Read data –Analyze data –Plot data Tools for research/analysis

54. Remember the vertical structure of the atmosphere Hydrostatic Eq. of State

55. If we assume T is constant with height (Isothermal)

56. If we assume T varies with height (Realistic)

57. If we assume T varies linearly with height (Not a bad assumption, in general)

59. Programming Exercise Read in data from two sounding files –Height –Potential temperature Compute pressure on each level –Isothermal atmosphere –Varying temperature –Constant lapse rate Use this information –Geostrophic wind –Temperature gradients

60. Programming Exercise Goals: programming concepts –Reading data –Arrays –Loops –Iteration Materials posted to ctools this afternoon/evening –Skeleton MatLAB program –Data –Instructions

61. Next Week Programming exercise in class Monday Start looking at quasi-geostrophic system –Scale analysis of equations in pressure coordinates –Quantify wave movement and development