![]() This means if the entire rainfall everywhere in India during a year was spread evenly over its area, the total accumulated water would be 116 cm high. To put this in perspective, in a normal year, India, as a whole, receives about 116 cm of rainfall over the entire year. Extreme weather events are indeed increasing in the Himalayan region.Also Read | Cloudburst in Dehradun, swollen rivers wash away bridges.But what is very clear is that events of extreme precipitation have been on the rise in the last few decades due to global warming it is expected, keeping in mind that trend, that cloudburst events might be on the increase as well.There is a paucity of past data on cloudbursts in addition, since only some of them get counted – only those that result in death and destruction – there is a problem of accuracy as well.Is the frequency of cloudbursts increasing? Landslides, flash floods, houses and establishments getting swept away and cave-ins lead to the deaths.It is the consequences of such heavy rain, especially in the hilly terrain, that causes death and destruction.The rainfall itself does not result in the death of people, though sometimes, the raindrops are big enough to hurt people in a sustained downpour.Why does cloudburst cause so many deaths? In addition, as pointed out earlier, cloudbursts get counted only when they result in largescale destruction of life and property, which happens mainly in mountainous regions.Hilly terrains aid in heated air currents rising vertically upwards, thereby, increasing the probability of a cloudburst situation.After a point, the raindrops become too heavy for the cloud to hold on to, and they drop down together in a quick flash. New drops are formed and existing raindrops gain in size.Raindrops, instead of dropping down, are carried upwards by the air current.Cloudbursts happen when saturated clouds are unable to produce rain because of the upward movement of very warm current of air.Cloudbursts do happen in plains as well, but there is a greater probability of them occurring in mountainous zones it has to do with the terrain.Why do cloudbursts happen only in the mountains and hilly areas? The many factors that have to come together to make a cloudburst event happen make them highly unlikely. Sometimes winds flowing in from the north west also aid the occurrence of cloudbursts.The moisture is usually provided by a low-pressure system (usually associated with cyclonic storms in the ocean) over the Gangetic plains associated with low level winds flowing in from the east.Cloudbursts mostly occur at elevations between 1,000-2,500 metres above sea level. The energy necessary for the cloudburst comes from the upward motion of air.These unstable clouds cause an intense rainstorm over a small area after becoming heavy enough and locked in the ridges and valleys between the hills.This upward motion of the clouds is known as an ‘orographic lift’. ![]() Such clouds usually cause rain, thunder and lightning.A cloudburst occurs when moisture-carrying air moves up a hilly terrain, forming a vertical column of clouds known as ‘cumulonimbus’ clouds.By this definition, 5 cm of rainfall in half an hour would also be classified as a cloudburst. The India Meteorological Department (IMD) defines a cloudburst as any event where 100 millimetres of rainfall have fallen in a span of an hour over a region that is 20-30 square kilometres in area. ![]() There is no universal definition of a cloudburst.
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