The process of continuous condensation in free air helps the condensed particles to grow in size. When the resistance of the air fails to hold them against the force of gravity, they fall on to the earth’s surface. So after the condensation of water vapour, the release of moisture is known as precipitation. This may take place in liquid or solid form.
Rainfall – Precipitation in the form of drops of water is called rainfall when the drop size is more than 5 mm.
Virga – Precipitation is called Virga when raindrops evaporate before reaching the earth while passing through dry air.
Drizzle – It is light rainfall with drop size being less than 0.5 mm, and when evaporation occurs before reaching the ground. Light rainfall; a drop size less than 0.5 mm.
Snowfall – When the temperature is lower than 0° C, precipitation takes place in the form of fine flakes of snow and is called snowfall. Moisture is released in hexagonal crystal form. These crystals form flakes of snow.
Sleet – It is frozen raindrops and refrozen melted snow-water. When a layer of air with a temperature above freezing point overlies a sub-freezing layer near the ground, precipitation takes place in the form of sleet.
Hailstones – Raindrops, which leave the warmer air, encounter the colder air below. As a result, they solidify and reach the ground as small pellets of ice not bigger than the raindrops from which they were formed. The rounded solid pieces of ice which reach the surface of the earth are called hailstones. These are formed by the rainwater passing through the colder layers. Hailstones have several concentric layers of ice, one over the other.
Read Also: Distribution of Rainfall in world
