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MADISON’S CURRENT WEATHER

MADISON’S CURRENT WEATHER. Madison Weather at 1000 AM CDT MON 24 JUN 2002 Updated twice an hour at :05 and :25 Sky/Weather: SUNNY Temperature: 81 F (27 C) Dew Point: 64 F (17 C)

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MADISON’S CURRENT WEATHER

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  1. MADISON’S CURRENT WEATHER Madison Weather at 1000 AM CDT MON 24 JUN 2002 Updated twice an hour at :05 and :25 Sky/Weather: SUNNY Temperature: 81 F (27 C) Dew Point: 64 F (17 C) Relative Humidity: 56% Wind: SW6 MPH Barometer: 30.11F (1019.6 mb)

  2. Current Surface Weather Map with Isobars (“iso” = equal & “bar” = weight), Fronts and Radar Isobars

  3. Rule of Thumb • The tighter the packing of the isobars, the stronger the winds!

  4. Current Surface Winds with Streamlines & Isotachs (“iso” = equal & “tach” = speed) L H L H H L

  5. Current Surface Weather Map with Isobars (“iso” = equal & “bar” = weight), Fronts and Radar Isobars

  6. Current Temperatures (°F) & Isotherms(“iso” = equal +”therm” = temperature)

  7. Tomorrow AM Forecast Map

  8. Announcements • Homework 1 • Get from our webpage • http://www.aos.wisc.edu/~hopkins/aos100/homework/ • Due this Thursday 27 June 2002

  9. ATM OCN 100 – Summer 2002LECTURE 4 ATMOSPHERIC PRESSURE: A Fundamental Weather Element • A. PRACTICAL PROBLEM • The pump problem: Why can’t water be lifted more than 30 ft?

  10. B. BASIC CONCEPTS:ATMOSPHERIC PRESSURE

  11. B. BASIC CONCEPTS:ATMOSPHERIC PRESSURE • Fundamental concepts • Importance of air pressure

  12. B. BASIC CONCEPTS:ATMOSPHERIC PRESSURE

  13. Current Surface Weather Map with Isobars (“iso” = equal & “bar” = weight), Fronts and Radar Isobars

  14. Low Pressure High Pressure Explaining Differences in Air Pressure L H

  15. Isobars -- lines of equal barometric pressure- use sea level corrected pressure L H H

  16. Display of Pressure Differences on a Weather Map - Isobars H L

  17. C. BAROMETRY • The Science of Barometry • How is air pressure measured? • Types of Barometers • Mercury Barometers • Aneroid Barometers where ...

  18. MERCURY BAROMETERS • Torricelli invention in 1643; • A self-supported column of mercury; • A balance between weight of atmosphere & weight of mercury in tube.

  19. Principles of a Mercury Barometer

  20. MERCURY BAROMETERS (con’t.)

  21. ANEROID BAROMETERS • Perfected in 1840’s; • An evacuated canister; • A balance between force of atmosphere & force of spring inside canister.

  22. Aneroid Barometer

  23. BAROGRAPH

  24. A pressure trace from a barographSee Fig. 5.5, Moran & Morgan (1997)

  25. C. BAROMETRY (con’t.) • Placement of Barometers • Pressure Units • Inches or millimeters of mercury; • Pounds per square inchormillibars. • The Millibar • Traditional meteorological pressure unit (a metric unit of force per unit area); • Sea level pressure 1000 millibars (or 1 bar).

  26. D. CLIMATOLOGY ofATMOSPHERIC PRESSURE • Spatial variation in Sea-level air pressure • Typical range: 900 mb to 1060 mb. • Temporal variation of Sea-level air pressure • Typically less than 1 mb per 3 hours.

  27. Average Sea Level Air Pressure & Atmospheric Circulation

  28. D. CLIMATOLOGY ofATMOSPHERIC PRESSURE • Why Do Variations occur in Pressure? • Temporal variation of Sea-level air pressure • Typically less than 1 mb per 3 hours.

  29. A pressure trace from a barographSee Fig. 5.5, Moran & Morgan (1997)

  30. Vertical Cross-Section of Air Converging AloftFig. 9.20 Moran & Morgan (1997)

  31. Map View of Flow around High Pressure Fig. 9.17 Moran & Morgan (1997)

  32. Vertical Cross-Section of Air Diverging AloftFig. 9.21 Moran & Morgan (1997)

  33. Map View of Flow around Low Pressure Fig. 9.18 Moran & Morgan (1997)

  34. AIR PRESSURE CLIMATOLOGY (con’t.)Vertical Variation

  35. AIR PRESSURE CLIMATOLOGY (con’t.)See Fig. 5.4 Moran & Morgan (1997) 50% of surface

  36. AIR PRESSURE CLIMATOLOGY (con’t) • Variation of air pressure with height • Lower atmosphere: 1mb per 10 m height rise; • or

  37. ALTIMETRY • Background • Pressure Altimeters Aneroid Barometers that indicate altitude rather than pressure • Computation

  38. AIR PRESSURE CLIMATOLOGY (con’t.)See Fig. 5.4 Moran & Morgan (1997) 1 mb drop for 10 meter height rise

  39. ALTIMETRY (con’t.) • Sources of error • Standard or model atmosphere does not always apply!

  40. Altimetry & Air Temperature(see Fig. 1 on pg. 113 Moran & Morgan, 1997)

  41. Flying with a pressure altimeterSee Fig. 1, pg. 113, Moran & Morgan (1997)

  42. Sea-Level Pressure Reduction • Desire – • To view only horizontal pressure variations on weather map; • Need – • To eliminate effects of topography from station pressure.

  43. Sea-Level Pressure Reduction (con’t.) • Result • Assume that pressure increases at fixed rate down to sea level.

  44. Isobars -- lines of equal barometric pressure- use sea level corrected pressure L H H

  45. Surface weather map June 2002

  46. Current Surface Weather Map with Isobars (“iso” = equal & “bar” = weight), Fronts and Radar Isobars

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