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Weather 101 and beyond

Weather 101 and beyond. Edward J. Hopkins Dept. of Atmospheric & Oceanic Sciences Univ. of Wisconsin-Madison Midwest Hot Air Balloon Safety Seminar “Hot Aireventure” Oshkosh 3 March 2001. Concerns of Balloonists. The Weather The Terrain (or Surface). Quiz.

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Weather 101 and beyond

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  1. Weather 101 and beyond Edward J. Hopkins Dept. of Atmospheric & Oceanic Sciences Univ. of Wisconsin-Madison Midwest Hot Air Balloon Safety Seminar “Hot Aireventure” Oshkosh 3 March 2001

  2. Concerns of Balloonists • The Weather • The Terrain (or Surface)

  3. Quiz • Ballooning (Fair) Weather is associated with High or Low Pressure? • Which way do winds blow around: High pressure? • Low pressure?

  4. WIND • What is Wind? • Why the wind? • Review of basic concepts

  5. ASOS Wind InstrumentsWind Vane (left) & Cup Anemometer (right)

  6. Aerovane Measures wind speed & direction

  7. BEAUFORT WIND FORCE SCALE[Modern version, Source: Federal Meteorological Handbook I]

  8. BEAUFORT WIND FORCE SCALE(con’t.)

  9. The wind responds to a Difference in air pressure

  10. BASIC CONCEPTS Air Pressure (con’t.)

  11. Low Pressure High Pressure Explaining Differences in Air Pressure

  12. Display of Pressure Differences on a Weather Map - Isobars

  13. Isobars -- lines of equal barometric pressure- use sea level corrected pressure

  14. AIR PRESSURE in the Vertical (con’t.)

  15. As a Sidebar… Altimetry • Since pressure decreases at a “reasonably” known rate of1 mb decrease per 10 meter rise or 0.01 inch of Hg per 10 feet, • then… pressure altimeters are barometers made to read in altitude. • But...

  16. Pressure Change with height depends upon Temperature of column- (It is really the density!)

  17. WHY THE WIND? (con’t.) • Reasons for Atmospheric Motions: • Buoyancy Effects or Dynamic Effects

  18. Daily Heating Heat Gain Heat Loss Daylight Nighttime

  19. January Temperatures - Madison, WI (1981-90) Nighttime Daylight Nighttime

  20. January Wind Speeds - Madison, WI (1981-90) Nighttime Daylight Nighttime

  21. July Temperatures - Madison, WI (1981-90) Daylight Nighttime Nighttime

  22. July Wind Speeds - Madison, WI (1981-90) Daylight Nighttime Nighttime

  23. ENERGY TRANSPORT: CONVECTION

  24. LAPSE CONDITIONSTemperature decreases with height

  25. ISOTHERMAL CONDITIONSTemperature remains constant with height

  26. INVERSION CONDITIONSTemperature increases with height

  27. U.S. STANDARD ATMOSPHERESee Fig. 1.9 Moran & Morgan (1997) Thermosphere Mesopause Mesosphere Stratopause Stratosphere Tropopause Troposphere

  28. WHY THE WIND? (con’t.) • Reasons for Atmospheric Motions: • Buoyancy Effects or Dynamic Effects

  29. Air Converging Aloft

  30. Air Diverging Aloft

  31. The Surface • The “Obvious” • Obstacles to take-off and landing (e.g., trees, power lines, animals) • The Surface and the Winds • Affects the Boundary Layer wind flow • Can produce local wind regimes

  32. Boundary Layer • Where we live • Extends from surface to approximately 3000 ft. (1000 m) • Consists of • Surface Boundary Layer (30 to 60 ft. & includes Anemometer Level) • Ekman or Spiral Layer(above 60 ft. to Free Atmosphere)

  33. Relative Surface RoughnessSource: Stull, 1995

  34. B. EXPLANATIONS of ATMOSPHERIC MOTION • Practical Problems • Historical Concepts • Forces of Motion & Newton's Laws

  35. An example of an equation of motionNASA

  36. PRESSURE GRADIENT FORCE

  37. PRESSURE GRADIENT FORCE(con’t.)

  38. ASSUMPTIONS For convenience, assume that: • Winds are nearly horizontal; • Atmosphere is in nearly “hydrostatic balance”i.e., air parcels do not accelerate upward or downward;

  39. HYDROSTATIC BALANCE CONCEPTSee Fig. 9.11 Moran & Morgan (1997)

  40. HORIZONTAL PRESSURE GRADIENT FORCE(con’t.)Direction is from High to Low pressure!

  41. HORIZONTAL PRESSURE GRADIENT FORCE (con’t.)See Fig. 9.1 Moran & Morgan (1997)Magnitude depends on isobar spacing!

  42. LOCAL WINDSFLOW RESPONDING TO PRESSURE GRADIENT FORCE - LOCAL WINDS • Assumptions: • Only Pressure gradient force operates; • Results from temperature differences • Acts for short time & short distances. • Examples: • Sea-Land Breeze Circulation • Mountain-Valley Breeze Circulation • City-Country Circulation

  43. Sea (Lake) Breeze(Graphics from UIUC WW2010)

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