Dry adiabatic lapse rate

  • As a parcel of air rises, it cools, but at what rate???

  • rate of temperature change with height is called the lapse rate

  • units of lapse rate are C km-1

  • Let's first consider an unsaturated parcel of air

  • unsaturated parcels cool at a rate of 10C km-1 - this is called the dry-adiabatic lapse rate -->>

  • What will be the parcel's temperature be at 1 km? ANSWER

QUESTION FOR THOUGHT:

Suppose the air pressure outside a conventional jet airliner flying at an altitude of 10 km is 250 mb. Further, suppose the air inside the aircraft is pressurized to 1000mb. If the outside air temperature is -50 C, what would be the temperature of this air if brought inside the aircraft and compressed at the dry adiabatic rate to a pressure of 1000mb (assume that a pressure of 1000mb is equivalent to an altitude of 0 m).