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Lapse Rate

Lapse Rate. Poisson equation:. ). d (. Lapse Rate. For an air parcel, going though dry adiabatic process,. So, is the dry adiabatic lapse rate when parcel moving up and down. There are three different lapse rates:. (Environmental) lapse rate,

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Lapse Rate

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  1. Lapse Rate • Poisson equation: ) d (

  2. Lapse Rate • For an air parcel, going though dry adiabatic process, So, is the dry adiabatic lapse rate when parcel moving up and down. • There are three different lapse rates: • (Environmental) lapse rate, • Dry adibatic lapse rate, • Moist adiabatic lapse rate,

  3. Stability Unstable Stable Neutral displacement no tendency to no tendency to displacement displacement continue or to return continue or to return tendency tendency Stable (oscillating)? or unstable (going away)? displacement p X

  4. Dry Static Stability • Oscillation due to the restoring force after displacement in a stratified stable atmosphere. • Starting from the vertical momentum equ. • Displacement Environment environment

  5. Dry Static Stability • In the air parcel (density) P adjusted to the environment immediately • Assume environment is hydrostatic balance

  6. Dry Static Stability • Back to the RHS of the momentum equation. • In the air parcel, d d • From ideal gas law and Poisson equation, one can get:

  7. Dry Static Stability • Therefore • In troposphere, the average of N is about 1.2 X 10-2 s-1. So, the period • implying that the parcel oscillating one cycle needs about 10 min.

  8. Dry Static Stability Environment lapse rate • So the atmosphere is statically stable the atmosphere is statically neutral the atmosphere is statically unstable (super adiabatic lapse rate) • This is for dry atmosphere. The moist atmosphere will be more sophisticated!

  9. Potential temperature Sounding (superadiabatic)

  10. T T T q q q Skew-T Log-P diagram q T Temperature Water vapor mixing ratio Potential Temperature or Dry adiabat Wet-bulb Potential Temperature or Moist adiabat

  11. Instability Superadiabatic (unstable)

  12. Instability

  13. Conditionally Unstable When the environment is unsaturated, it is stable. When the environment is saturated, it is unstable. warmer colder Environment

  14. Potential Instability • (Also called convective instability, thermal instability.) The state of an unsaturated layer or column of air in the atmosphere with a wet-bulb potential temperature (or equivalent potential temperature) that decreases with elevation. • If such a column is lifted bodily until completely saturated, it will become unstable (i.e., its temperature lapse rate will exceed the saturation-adiabatic lapse rate) regardless of its initial stratification. • From AMS

  15. LCL After lifted (dp) LCL Potential Instability q T Unstable Absolutely Stable T Air Layer dp Td

  16. Inversion • Subsidence inversion • Radiative inversion • Mixed layer inversion • Frontal inversion

  17. Subsidence Inversion

  18. Subsidence Inversion High pressure systems

  19. Subsidence Inversion

  20. Mixed Layer Inversion • Shear instability When there is no wind shear, When there is shear Ri < 0.25 Shear instability (unstble)

  21. Mixed Layer Inversion

  22. Mixed Layer Inversion

  23. Subsidence Inversion High pressure systems

  24. Radiative Inversion

  25. Frontal Inversion

  26. Frontal Inversion

  27. Frontal Inversion OUN LCH GGG DOC

  28. Frontal Inversion

  29. Frontal Inversion

  30. Frontal Inversion

  31. Frontal Inversion

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