Cloud Burst A Natural Calamity
Normal rain in small drops comes to ground with no force at all (Stoke’s law*). This rainwater does not flow down the slope & mostly absorbed into ground. So, it is good for agriculture and ground water.
A heavier rain falls with larger drops & with force sufficient enough to cause soil erosion. This has harmful effect on soil. Humus, the fertile layer of soil is washed away with water in the rivers & finally into see. This rain does not help much in raising water strata of ground.
If there is around or more than 100 mm of rain within one hour at any place, then this Rain Tsunami is known as Cloud burst. It is a very dreaded calamity in weather science.
Natural factors responsible for Cloud Burst
(Courtesy Times of India)
It occurs during big thunderstorms. A lot of water containing clouds are trapped with heavy wind currents & are driven up as column, to higher altitude where they condence to form water droplets. These droplets coalase together to form bigger drops (Logmuir’s precipitation effect**). Sometimes, this wind column suddenly stops (mostly over hilltops or over a valley). The wind column can not hold the enormus ammount water. This entrapped water suddenly descends down to ground. It may pour tons of water over a hectare of ground in a very short time. Force with which water falls, results in great destruction by uprooting trees, destroying buildings, dislodging big boulders in hill area with mountains of mud sludge. The huge amount of water along with boulders mud sludge destroys everything that comes in its way.
HEAVY RAINS CAN BE PREDICTED BY WEATHER SCIENTISTS, BUT CLOUD BURSTS CAN NOT BE PREDICTED
*Stoke’s Law:- When a small drop falls through atomosphere its dscent becomes uniform. This phenominon is due to bouyancy & friction of atomosphere. This drop has negligible force when it reaches ground. While bigger drops with much weight fall with more speed & have damaging effect.
**Logmuir’s precipitation effect:- Logmuir was first scientist to experiment with artificial rain. He seeded ions of silver iodide in atomosphere, at certain height from ground over a large area. Drops of atomospheric water vapour condensed (coalased) arround particles of silver iodide. These drops became too heavy (heavier than crtical weight) so they camedown (precipitated) on earth as artificial rain.