II' Synoptic Atmospheric Destabilization Processes

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II. Synoptic Atmospheric Destabilization Processes

• Upper Level Mixed Layer
• Synoptic Lifting
• Dynamic Destabilization
• Differential Advection

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Static Stability and Instability

• Static Stability push an air parcel upward
  (downward) and it will fall (rise) back to its
  original position transforming the work exerted
  to accelerate the parcel into the kinetic energy
  of the parcels return movement.
• Static Neutrality push an air parcel upward
  (downward) and it will continue its motion
  without further acceleration.
• Static Instability push an air parcel upward
  (downward) and it will continue to accelerate its
  motion upward (downward)

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Dry Adiabats

• Dry Adiabats (lines of constant theta on a
  thermodynamic diagram)

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Moist Adiabats

• Moist Adiabats (lines of constant
  pseudo-equivalent potential temperature on
  thermodynamic diagram)

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Dry Adiabatic Lapse Rate
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Moist Adiabatic Lapse Rate
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Static Stability
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Destabilization

• Increase Lapse Rate at middle levels
• Mix air vertically
• Warm below
• Advection
• diabatic
• Cool above
• Advection
• diabatic
• Increase low level moisture and temperature
• Daytime heating
• Warm moist advection, Sawyer-Elliasen surge
• Maintain inversion (cap) separating low level
  moisture and heat from increased upper level
  lapse rate

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Layer Lifting
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Differential Advection

• Layer aloft moving at a different velocity than
  one below
• Cold air advection Aloft
• Warm or moist air advection below

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Example of Differential Advection
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Elevated Mixed Layer

• Deep dry mixing of a dry daytime boundary layer
  produces high lapse rate through deep layer
• Deep dry adiabatic layer (steep lapse rate)
• Very dry layer, nearly constant vapor mixing
  ratio
• Best layers formed in regions of very dry air
  (too make dry lapse rate) found in
• Deserts
• High plateau or lee side of a mountain range

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Elevated Mixed Layer

• Deep, warm, dry well mixed layer advected over
  the top of a relatively cool (potential
  temperature-wise) layer forming a capping
  inversion
• Boundary layer below inversion moistened and
  warmed creating conditional instability
• Daily heating and evapo-transpiration
• Advection from a moist region

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EML Moving From Rockies
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Dynamic Destabilization

• Quasi-geostrophic sinking motion in the right
  exit region of the jet forces subsidence and a
  capping subsidence inversion
• Sawyer-Elliasen Circulation advects warm air
  under dry destabilized layer completing the
  formation of loaded gun sounding
• Progression into the right entrance region
  initates rising motion that pulls trigger

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Load the Gun
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Pull the Trigger!
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High Elevation Sounding
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Loaded Gun Sounding