Search Results - Precipitation (meteorology)

In meteorology, precipitation (also known as one class of hydrometeors, which are atmospheric water phenomena) is any product of the condensation of atmospheric water vapour that is deposited on the earth's surface.^[1] It occurs when the atmosphere, a large gaseous solution, becomes saturated with water vapour and the water condenses and falls out of solution (i.e., precipitates).^[2] Two processes, possibly acting together, can lead to air becoming saturated cooling the air or adding water vapour to the air.

Precipitation that reaches the surface of the earth can occur in many different forms, including rain, freezing rain, drizzle, snow, ice pellets, and hail. Virga is precipitation that begins falling to the earth but evaporates before reaching the surface. Precipitation is a major component of the water cycle, and is responsible for depositing most of the fresh water on the planet. Approximately 505,000&_160;km³ (121,000&_160;cu&_160;mi) of water falls as precipitation each year, 398,000&_160;km³ (95,000&_160;cu&_160;mi) of it over the oceans.^[3] Given the Earth's surface area, that means the globally-averaged annual precipitation is about 1&_160;m (39&_160;in), and the average annual precipitation over oceans is about 1.1&_160;m (43&_160;in).

Precipitation can be divided into three categories, based on whether it falls as liquid water, liquid water that freezes on contact with the surface, or ice. Each of these categories can be further subdivided