Precipitation occurs when tiny droplets of water, ice or frozen water vapor join together into masses too big to be held above the earth. They then fall to ground as precipitation.
The term precipitation denotes all forms of water that reach the earth from the atmosphere. Usual forms are rainfall, snowfall, hail, frost and dew. Of all these, only the first two contribute significant amounts of water. Magnitude of precipitation varies with time and space.
Conditions for precipitation to form:
- The atmosphere must have moisture.
- There must be sufficient nuclei present to aid condensation.
- Weather conditions must be good for condensation of water vapour to take place.
- The products of condensation must reach the earth.