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 p Unstable Stable Neutral no tendency to no tendency to displacement no tendency to no tendency to displacement displacement continue or to return continue or to return tendency tendency p Stable (oscillating)? or unstable (going away)? displacement 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 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 the atmosphere is statically stable 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!

Sounding Potential temperature (superadiabatic)

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

Instability Superadiabatic (unstable)

Instability

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

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) Unstable Absolutely Stable Air Layer dp LCL T Td

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

Mixed Layer Inversion

Subsidence Inversion High pressure systems

Radiative Inversion

Frontal Inversion

Frontal Inversion

Frontal Inversion LCH GGG OUN DOC

Frontal Inversion

Frontal Inversion

Frontal Inversion

Frontal Inversion