AIR PRESSURE FORCES AND WIND - PowerPoint PPT Presentation

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AIR PRESSURE FORCES AND WIND

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  1. AIR PRESSURE FORCES AND WIND

  2. PRESSURE GRADIENT FORCE Definition: The difference in atmospheric pressure per unit distance PGF acts at right angles to isobars of equal pressure H L 102.2 99.8 101.4 100.6 600 km Pressure Gradient Force = 2.4 kPa / 600 km = 0.4 kPa / 100 km

  3. Where are winds strongest ? Oct 18, 2004 Solution: HUDSON BAY Check the spacing of the isobars of equal surface pressure

  4. CORIOLIS FORCE Source: NASA

  5. FRICTION FORCE Surface roughness decreases wind speed Reduces impact of Inertial Coriolis Force Winds cross isobars, spiralling out of ANTICYCLONES (H), and into CYCLONES (L) H L

  6. Can you infer wind direction & speed? weather.unisys.com

  7. WINDS ALOFT ARE DISTINCT H L Air tends to be unstable in low pressure (tendency to rise) Air tends to be stable in high pressure (tendency to fall)

  8. GLOBAL ATMOSPHERIC CIRCULATION

  9. MAIN PRESSURE ZONES • Equatorial Low Pressure Trough • Subtropical High Pressure Cells • Subpolar Low Pressure Cells • 4. Weak Polar High Pressure Cells

  10. Intertropical Convergence Zone

  11. How does this relate to the “jet stream”?

  12. Geostrophic wind (above strong influence of friction)

  13. WIND SMALL-SCALE & LOCAL SYSTEMS CHAPTER 10

  14. WIND VANE & CUP ANEMOMETER

  15. SONIC ANEMOMETER ULTRASONIC SOUND WAVES DETERMINEWIND SPEED, DIRECTION & TEMPERATURE Sonic transducers

  16. SNOWDRIFT

  17. SNOWDRIFT http://www.wrds.uwyo.edu/wrds/rmfres/fendrift.html

  18. Effect of Surface Roughness and Instability on Windspeed

  19. Depth of mixing depends on: Surface Heating WIND SPEED TOPOGRAPHY SURFACE ELEMENTS

  20. Effect of Eddies on Wind Inclination UNSTABLE STABLE

  21. MOUNTAIN WAVES

  22. ROTOR CLOUDS