Chapter 6 - Atmospheric Processes

adiabatic process

when air parcels rise and sink in unsaturated conditions, no heat is lost or gaines

dry adiabatic lapse rate

as air rises in unsaturated conditions, temp decreases by 10 C, dewpoint by 2 C

moist adiabatic lapse rate

as air rises in saturated conditions, temp and dewpoint decrease by 6 C

stable environment

one with little or no unexpected change

absolutely stable environment

air parels will be colder than their environment and sink back to their original position

unstable environment

one in which things could change and do so quickly

absolutely unstable environment

air parcels are warmer than their environment and are forced to rise

conditionally stable/unstable

unsaturated parcels sink, saturated rise

neutrally stable

environmental lapse rate = dry-adiabatic lapse rate

neutrally stable environment

unsaturated parcels stay put

free convection

sinking cold air results in blue sky between clouds

Lifting Condensation Level (LCL)

the level at which a parcel of air when lifted dry adiabatically, would become saturated

Convective Condensation Level (CCL)

the height above the surface marking the base of a cumuliform cloud

cloud base equation

(T-Td)/2.5 x 1,000 ft

Level of Free Convection

when parcel’s temp > environment, rises freely

Equilibrium Level (EL) / Level of Neutral Buoyancy (LNB)

level above the LFC where parcel temp < environment, stops rising

warm fronts

gentle lifting of warm air across 100s of miles of colder dense air near the surface

stratiform clouds (continuous rainfall)

altostratus, stratus, nimbostratus, cirrostratus

cold fronts

warm air forced up by approaching denser cold air

cumuliform clouds

cumulus humulis, cumulus congestus, cumulonimbus