Saturation can occur by way of atmospheric mechanisms that cause the temperature of an air mass to be cooled to its dew point or frost point . Orographic precipitation occurs when air is forced to rise because of the physical presence of elevated land. As the parcel rises it cools as a result of adiabatic expansion at a rate of approximately 10 degrees Celsius per 1000 meters until saturation . The large amounts of precipitation along the west coast of Canada are due mainly to this process.
Convectional precipitation is associated with surface heating of the air at the ground surface.
If enough heating occurs, the mass of air becomes warmer and lighter than the air in the surrounding environment, and just like a hot air balloon it begins to rise, expand, and cool. When sufficient cooling has taken place saturation occurs forming precipitation. This process is active in the interior of continents and near the equator forming cumulus clouds and thunderstorms . Rain is usually the precipitation type that is formed, and in most cases this moisture is delivered in large amounts over short periods of time in extremely localized areas. Convergence or frontal precipitation takes place when two masses of air come together.