Lapse Rate Poisson equation d Lapse Rate For

Lapse Rate • For an air parcel, going though dry adiabatic process, So, is

Stability Stable Neutral Unstable displacement no tendency to continue or to return p displacement

Dry Static Stability • Oscillation due to the restoring force after displacement in a

Dry Static Stability • In the air parcel (density) P adjusted to the environment

Dry Static Stability • Back to the RHS of the momentum equation. In the

Dry Static Stability • Therefore • In troposphere, the average of N is about

Dry Static Stability • So Environment lapse rate the atmosphere is statically stable the

Sounding Potential temperature (superadiabatic)

Skew-T Log-P diagram q T Temperature Potential Temperature or Dry adiabat Water vapor mixing

Conditionally Unstable When the environment is unsaturated, it is stable. When the environment is

Potential Instability • (Also called convective instability, thermal instability. ) The state of an

Potential Instability q T LCL After lifted (dp) Air Layer dp Unstable LCL Td

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

Subsidence Inversion High pressure systems

Mixed Layer Inversion • Shear instability When there is no wind shear, When there

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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, • Dry adibatic lapse rate, • Moist adiabatic lapse rate,

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

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

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

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:

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.

Dry Static Stability • So Environment lapse rate 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!

Sounding Potential temperature (superadiabatic)

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

Instability Superadiabatic (unstable)

Instability

Conditionally Unstable When the environment is unsaturated, it is stable. When the environment is saturated, it is unstable. viro En colder warmer nm ent

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

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

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

Subsidence Inversion

Subsidence Inversion High pressure systems

Subsidence Inversion

Mixed Layer Inversion • Shear instability When there is no wind shear, When there is shear Ri < 0. 25 Shear instability (unstble)

Mixed Layer Inversion

Subsidence Inversion High pressure systems

Radiative Inversion

Frontal Inversion

Frontal Inversion LCH GGG OUN DOC

Frontal Inversion