Adiabatic Lapse Rate

 When 'Shallow lapse rate' is referenced it means the Environmental lapse rate is slow, or as you go up the temperature doesn't change much.

A rising parcel of air will cool at approx one of the following rates:

Dry (unsaturated) Adiabatic Rate is:
    3ºC per 1000 ft

Saturated (wet) Adiabatic Rate
    1.5º per 1000 ft

Standard lapse rate 1.98 per 1,000 ft

The greatest determiner of wether weathering will be stable or not is the environmental lapse rate.  The steeper the ELR the more unstable the weather.  That is the faster it gets colder at altitude the more unstable the weather.

Stable air
Means
    Smooth flying
    Poor vis
    Steady rain
    Stratus Layer cloud
    Fog
    Shallow lapse rate
    Inversion
    Warm air moving over cold air

Surface cooling causes stable air
    Radiation at night
    Influx of cold air (cold advection - horizontally moving cold air)
Warm air aloft also causes stable air
    Radiation cooling
    Warm advection aloft
    Large scale sinking of air

Subsidence inversions - Subsidence is the sinking of air, either from a high pressure system or on the leeward side of a mountain. The air warms as it descends. The air at the top of a high pressure system warms more as it sinks than the bottom of the high pressure system.

Unstable air
Means
    Bumpy flying
    Good visibility
    Showery rain
    Cumulus cloud (heaps)
    Thunderstorms
    Steep lapse rate (colder faster as you rise)
    High temp / dewpoint spread

Warm earth can warm up cold air and cause unstable air. (eg in the fall). Cold air comes in, eg from the north (polar) region and the warm earth warms it up.

Stable air = temps that change slowly with altitude

Unstable air = temps that change rapidly with altitude

Lapse rate types:
    Steep Lapse Rate - Unstable
    Shallow Lapse Rate - Unstable
    Inversion - Stable
    Isothermal Layer - Stable

Radiation
    Reflection of the earth's rays
Conduction
    Warm air contacting cold air
Advection
    Horizontal movement of air
Convection
    Unequal surface heating

Ways to cool the earths surface (stable air condition)
    Cold air advection
        Cold air moves into a region at low altitude cooling it
    Radiation cooling
        After the sun has set the earth radiates heat and then cools the air around it after the heat has left

Lifting processes that can cause instability: Know these
Convection
    Unequal surface heating
Convergence
    Excess air rises as pressure systems meet
Mechanical turbulence
    Surface friction
Orographic lift
    air moving up hills / mountains (anabatic)
Frontal lift
    Advancing air being pushed up by cold air on the bottom








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