Environmental Lapse Rate
The rate at which the air temperature decreases as you move higher in the atmosphere.
The rate at which a parcel of air cools as it rises depends on the relative humidity of the air contained in the parcel. If a parcel has a relative humidity less than 100% we say it is dry.
A dry parcel cools at a constant rate known as the dry adiabatic lapse rate and is equal to about 1įC/100m. As the parcel continues its ascent, it continues to cool, and it has less and less capacity to hold moisture. Eventually the parcelís relative humidity reaches 100%, when it is said to be saturated. The temperature at which this happens is called the dew point temperature.