FORMS OF PRECIPITATION
Some of the common forms of precipitation are discussed as follows:
- Rainfall :
It is the main form of precipitation in India.
When the size of water drop is large than 0.5 mm, it is called rainfall.
The maximum size of a raindrop is about 6 mm. Rainfall may be light, moderate and heavy if intensities of rainfall are 2.5 mm/hr. 2.5 mm to 7.5 mm/hr and more than 7.5 mm/hr respectively.
- Snow :
Snow is another important form of precipitation.
Snow consists of ice crystals which usually combine to form flakes. New fresh snow has an initial density from 0.06 to 0.15 g/cm and the average value is assured to be 0.1 g/cm3
In India, snow falls in the Himalayan region.
- Drizzle :
A fine sprinkle of numerous water droplets of size less than 0.50 mm and intensity less than 1 mm/ h is known as drizzle.
The drops are so small that they seem to float in air.
- Glaze :
When rain or drizzle comes in contact with cold ground at around 0°C, the water drops freeze to form an ice coating called glaze or freezing rain.
- Sleet :
They are frozen raindrops of transparent grains, which form when rain falls through sub freezing temperature.
- Hail :
Precipitation in the form of balls or irregular lumps of ice of size more than 8 mm in diameter is called hail.
Hails occurs in violent thunder storms in which vertical currents are very strong. Hailstones may be spherical. conical or irregular shape.
- Dew :
Dew forms directly by condensation on the ground mainly during the night when the surface has been cooled by the outgoing radiation.