1 / 57

MET 61 Introduction to Meteorology - Lecture 10

MET 61 Introduction to Meteorology - Lecture 10. Atmospheric Dynamics Dr. Eugene Cordero Ahrens: Chapter 9 W&H: Chapter 7, pg 271-296 Class Outline: Principle forces in the atmosphere Pressure gradient Coriolis Geostrophic wind. Atmospheric forces.

salaam
Download Presentation

MET 61 Introduction to Meteorology - Lecture 10

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. MET 61 Introduction to Meteorology - Lecture 10 Atmospheric Dynamics Dr. Eugene Cordero Ahrens: Chapter 9 W&H: Chapter 7, pg 271-296 Class Outline: • Principle forces in the atmosphere • Pressure gradient • Coriolis • Geostrophic wind MET 61 Introduction to Meteorology

  2. Atmospheric forces • Fundamental Forces in the atmosphere • Pressure Gradient Force • Gravity • Rotation of the Earth • Friction MET 61 Introduction to Meteorology

  3. Pressure • Ultimately responsible for our weather MET 61 Introduction to Meteorology

  4. Determines the direction and speed of winds: Predominate force in atmospheric flows Can help explain general circulation of atmosphere. Horizontal Pressure Changes MET 61 Introduction to Meteorology

  5. MET 61 Introduction to Meteorology

  6. MET 61 Introduction to Meteorology

  7. MET 61 Introduction to Meteorology

  8. Pressure gradient: Dependent on spacing between isobars Dense or tight clustering of isobars - strong or large pressure gradient Weak clustering of isobars - weak pressure gradient Pressure Gradient Force Pressure gradient directed from high to low pressure MET 61 Introduction to Meteorology

  9. MET 61 Introduction to Meteorology

  10. Orient yourself (location, date and time) Identify what you are looking at Determine the interval of the field Reading a weather map MET 61 Introduction to Meteorology

  11. MET 61 Introduction to Meteorology

  12. MET 61 Introduction to Meteorology

  13. C • A • B • At what local time is this map valid? • What fields are we looking at? • Indicate the direction of the pressure gradient force at points A-C. MET 61 Introduction to Meteorology

  14. MET 61 Introduction to Meteorology

  15. Atmospheric Thickness MET 61 Introduction to Meteorology

  16. MET 61 Introduction to Meteorology

  17. Hypsometric Equation • Combination of ideal gas law with hydrostatic balance. • Relates atmospheric thickness with average temperature. • Thickness of atmosphere relates to difference between two atmospheric layers; zt (m) = thickness between two pressure levels MET 61 Introduction to Meteorology

  18. MET 61 Introduction to Meteorology

  19. MET 61 Introduction to Meteorology

  20. knots MET 61 Introduction to Meteorology

  21. The rotation of the Earth • Rockets, migrating birds, and large scale weather systems are all deflected due to the rotation of the Earth. • The Earth’s rotation causes both • Translational movement • Rotational movement • The Coriolis Force is the name of this rotational force that deflects motion. MET 61 Introduction to Meteorology

  22. MET 61 Introduction to Meteorology

  23. MET 61 Introduction to Meteorology

  24. MET 61 Introduction to Meteorology

  25. Coriolis Force • Affects direction, not speed of object • Maximum at the poles • Zero at the equator (only translational movement) • Fc=2W v sinj • W - omega - • Earth’s rotational rate • W =360 degrees/24 hours or • v - wind speed • j - latitude Calculate Coriolis force for wind moving at 10m/s 2 radians/86400 seconds=7.27x10-5 s-1 2(7.27x10-5 s-1)(10m/s)(sin37)=8.8e-4 m/s2 MET 61 Introduction to Meteorology

  26. Take home message: N. Hem - deflects air to the right S. Hem - deflects air to the left Relatively small acceleration, thus requires long periods of time to influence motion. Coriolis Force MET 61 Introduction to Meteorology

  27. Geostrophic balance • Geostrophic balance is balance between: Pressure gradient force and Coriolis force • Result: flow of air is parallel to isobars • friction is assumed to be zero MET 61 Introduction to Meteorology

  28. Geostrophic Wind example Northern Hemisphere L Pressure Gradient Force 1000 mb 1004 mb Geostrophic Wind 1008 mb Coriolis Force H MET 61 Introduction to Meteorology

  29. MET 61 Introduction to Meteorology

  30. MET 61 Introduction to Meteorology

  31. MET 61 Introduction to Meteorology

  32. MET 61 Introduction to Meteorology

  33. A • B • C • Indicate with arrows the pressure gradient and Coriolis force at A, B and C. • Indicate the direction of the wind at each point. • Which point do you think the wind will be stronger?

  34. Geostrophic Wind • Assume friction is zero • Flow is parallel to isobars • Balance between pressure gradient and Coriolis force  - density, f - Coriolis parameter (=2 W sin j) Vg - geostrophic wind speed • d – distance between isobars •  p – pressure difference MET 61 Introduction to Meteorology

  35. http://www.met.sjsu.edu/weather/avn.html MET 61 Introduction to Meteorology

  36. Estimate the geostrophic wind speed for this situation MET 61 Introduction to Meteorology

  37. http://www.met.sjsu.edu/weather/avn.html MET 61 Introduction to Meteorology

  38. Geostrophic Wind with Friction Northern Hemisphere Friction decreases speed of wind, thus Coriolis force is weaker. L Pressure Gradient Force 1000 mb 1004 mb Geostrophic Wind Friction 1008 mb Coriolis Force H MET 61 Introduction to Meteorology

  39. MET 61 Introduction to Meteorology

  40. MET 61 Introduction to Meteorology

  41. MET 61 Introduction to Meteorology

  42. B • A MET 61 Introduction to Meteorology

  43. B • A MET 61 Introduction to Meteorology

  44. MET 61 Introduction to Meteorology

  45. MET 61 Introduction to Meteorology

  46. MET 61 Introduction to Meteorology

  47. MET 61 Introduction to Meteorology

More Related