Module 8- Adiabatic Processes and Clouds
Adiabatic process- air expands at high altitude due to lower atmospheric
pressure, uses heat energy to expand parcel, it is thus cold at high
temperature, doesn’t interchange with heat
Sinking, compressed, and warms
Dry adiabatic lapse rate DALR- warming and cooling remains constant,
applies only to unsaturated air
Moist adiabatic lapse rate- less than DALR, varies with temperature as water
condenses into clouds past the dew point as air cools
Absolutely stable atmosphere- environmental lapse rate is less than saturated
adiabatic, parcel is cooler than environment, tendency to go down
Absolutely unstable- environmental lapse rate is greater, parcel is warmer
than environment, tendency to go up
conditional instability- unsaturated air lifted to saturation where we don’t
know where it goes, environmental lapse rate in between
How do clouds form
Orographic uplift- air deflect over a mountain, adiabatic cooling and
promotes cloud
Radiation fog, valley fog
Advection fog
Upslope fog
Evaporation fog