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Constant Pressure Maps

Constant Pressure Maps. ATMO 4300 Spring 2008. Two Related Variables . Height and Pressure On a surface weather map, height is constant and pressure varies What height is used and why?. Surface Weather Map Figure from www.rap.ucar.edu/weather/model. Question.

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Constant Pressure Maps

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  1. Constant Pressure Maps ATMO 4300 Spring 2008

  2. Two Related Variables • Height and Pressure • On a surface weather map, height is constant and pressure varies • What height is used and why?

  3. Surface Weather MapFigure from www.rap.ucar.edu/weather/model

  4. Question • Where does the information come from that is plotted on a surface weather map? • Mostly from ASOS (Automated Surface Observation System)

  5. ASOS

  6. Upper Air Maps • Also called constant pressure maps • On these maps, pressure is constant and height varies

  7. 500 mb Map

  8. Question • Where does the information come from that is plotted on a constant pressure map?

  9. Upper Air Observations • Radiosonde • Measures temperature, pressure, humidity • Rawinsonde - wind • Figure from www.erh.noaa.gov/er/gyx

  10. Launching a Radiosonde Photo from www.srh.noaa.gov/mob/balloon.shtml; map from www.srh.noaa.gov/bmx/upperair/radiosnd.html

  11. Depicting Upper Air Data • 1. Constant Pressure Maps • 2. Temperature/height diagram: Vertical profile of temperature, dew point and wind

  12. Thermodynamic Diagram

  13. Depicting Upper Air Data • 1. Constant Pressure Maps

  14. Standard Upper Air Maps PressureHeight (ft)Height (m) • 200 mb 39,000 ft 12,000 • 300 mb 30,000 ft 9000 • 500 mb 18,000 ft 5500 • 700 mb 10,000 ft 3000 • 850 mb 5,000 ft 1500

  15. Constant Pressure Maps • Pressure decreases with height • Rate of decrease varies • Height of a given pressure varies 500 500 500 up 500

  16. 500 mb Map

  17. Question • Why does the height of a constant pressure surface vary from place to place?

  18. Standard AtmosphereFigure from ww2010.atmos.uiuc.edu

  19. Non Standard TemperaturesFigure from ww2010.atmos.uiuc.edu

  20. Temperature & Density • Which column has the greater density? • Pressure decreases at a greater rate with height in the cold air • Figure from apollo.lsc.vsc.edu/classes/met130

  21. Construction of a 500 mb Mapupper left map from www.srh.noaa.gov/bmx/upperair/radiosnd.html 1 3 2 500 4 500 500 500

  22. Use of Const. Press. Maps • 850 mb map - Low level winds – Low Level Jet (LLJ) - Temperature advection – vertical motion - Moisture advection - Frontal zones

  23. Use of Const. Press. Maps • 700 mb map - Temperature advection – vertical motion - Winds - Relative Humidity T-Td = 5 or less: possible clouds/ upward motion - Quick look at possible cap: T > 12-14C

  24. Use of Const. Press. Maps • 500 mb map - Identify Long-waves & Short-waves - Vorticity – related to vertical motion - Wind flow patterns (see following slides)

  25. Upper-Level Flow • Zonal Flow – dominant W to E flow • Meridional Flow – large north/south component to the flow

  26. Meridional FlowImage from www.rap.ucar.edu/weather

  27. Split FlowDiagram from www.theweathrprediction.com/blocking Note the northern branch and southern branch of the westerlies

  28. Cut-Off Low Diagram from www.theweathrprediction.com/blocking

  29. Omega BlockDiagram from www.theweathrprediction.com/blocking

  30. Rex BlockDiagram from www.theweatherprediction.com/blocking

  31. Use of Const. Press. Maps • 300/250/200 mb maps - Locate Polar & Subtropical Jet Streams - Locate Jet Streaks (Jet Max)

  32. Polar Jet

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