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Climatology Lecture 5

Climatology Lecture 5. ‘ Vertical Motion in the Atmosphere’ …Continued. Michael Palmer Room 119, Atmospheric Physics mpalmer@atm.ox.ac.uk. Dry Example: Absolute Stability Surface Temp = 34 o C. Stable Air No convection No Rain. Environ Temp. Parcel Temp. Temperature.

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Climatology Lecture 5

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  1. ClimatologyLecture 5 ‘Vertical Motion in the Atmosphere’ …Continued... Michael Palmer Room 119, Atmospheric Physics mpalmer@atm.ox.ac.uk

  2. Dry Example: Absolute Stability Surface Temp = 34 oC Stable Air No convection No Rain Environ Temp Parcel Temp Temperature

  3. Dry Example: Absolute Stability Surface Temp = 34 oC Stable Air No convection No Rain Environ Temp Parcel Temp Temperature

  4. Moist Example: Absolute Instability Surface Temp = 34 oC Unstable Air Convection Rain Condensation Level Parcel Temp Temperature Environ Temp

  5. Wet Example: Conditional Instability Unstable Air Convection Rain Level of free convection Condensation Level Temperature

  6. Vertical Motion • Potential Instability • Absolute Stability Topographically forced stable cloud Pollution dispersion climatology

  7. Potential Instability • Conditional instability involves convective ascent of parcels of air • Potential instability involves large scale ascent of layers of air • Instability is potential since the air is stable until lifted by an appropriate amount • Potential Instability may occur if a layer of air is very moist at the bottom but very dry aloft

  8. Stability depends on ELR Temperature Environ Temp Parcel Temp

  9. Stability depends on ELR Temperature Environ Temp Parcel Temp

  10. Z Temperature

  11. B’ New ELR A’ Z B Old ELR A Temperature

  12. Z B A Temperature

  13. A’ Z A Temperature

  14. B’ A’ Z B A Temperature

  15. B’ Z A’ B A Temperature

  16. B’ More unstable A’ Z B Stable A Temperature

  17. Potential Instability • The initial lapse rate in the layer AB is stable • On lifting of the entire layer, the base reaches condensation quickly, since it is moist - the slower rate of cooling (SALR) is applicable - but the top of the layer cools at the DALR • The new layer A’B’ is unstable for rising parcels.

  18. Vertical Motion • Potential Instability • Absolute Stability Topographically forced stable cloudPollution dispersion climatology

  19. Absolute Stability ??

  20. Absolute Stability

  21. Absolute Stability

  22. Environmental lapse rate Z Dry adiabatic lapse rate Temperature

  23. Environmental lapse rate 1 Z Dry adiabatic lapse rate Temperature

  24. Environmental lapse rate 1 Z 2 Dry adiabatic lapse rate Temperature

  25. Environmental lapse rate 1 3 Z 2 Dry adiabatic lapse rate Temperature

  26. Environmental lapse rate 1 3 4 Z 2 Dry adiabatic lapse rate Temperature

  27. Environmental lapse rate 1 3 5 4 Z 2 Dry adiabatic lapse rate Temperature

  28. Absolute Stability 1 3 4 2

  29. Absolute Stability

  30. Absolute Stability Air hotter and drier on leeward side

  31. H E I G H T TEMPERATURE

  32. H E I G H T Subsidence Inversion TEMPERATURE

  33. H E I G H T Subsidence Inversion Surface Radiation Inversion TEMPERATURE

  34. H E I G H T Early Morning TEMPERATURE

  35. H E I G H T Daytime Early Morning TEMPERATURE

  36. (Unstable) (Near neutral stability) Γ (dashed) – DALR Solid - ELR

  37. Stack Height • Statistical characteristics of surface and non-surface inversion layers: depth, strength, frequency • longer stacks: increased eddy diffusion • effective stack height: H = hs + dh hs= physical height of stack dh = f (Stability, wind speed,stack exit velocity, stack diameter, temperature of emission, emission rate)

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