Sharp rise in cloudbursts

Source: HT

Context:

Sudden, “highly-localised rains” in Amarnath, Jammu and Kashmir, recently caused flooding.

About

What is a cloudburst?

A cloudburst refers to an extreme amount of rain that happens in a short period, sometimes accompanied by hail and thunder.

The India Meteorological Department (IMD) defines it as unexpected precipitation exceeding 100mm (or 10 cm) per hour over a geographical region of approximately 20 to 30 square km.

Significant amounts of rainfall such as this can result in floods.

Conditions favorable for Cloud Burst:

Hilly areas are more prone to cloud burst. The topographical conditions like steep hills favour the formation of these clouds.

And also the devastations, as water flowing down the steep slopes bring debris, boulders and uprooted trees with great velocity damaging any structure that comes in their way.

Why do cloudbursts occur in hilly areas like Amarnath?

Experts have said it is difficult to predict when exactly a cloudburst will occur, and there is little definitive data on the exact number of cloudbursts that occur in India.

In hilly areas, sometimes saturated clouds ready to condense into rain cannot produce rain, due to the upward movement of the very warm current of air.

Instead of falling downwards, raindrops are carried upwards by the air current.

New drops are formed and existing raindrops increase in size.

After a point, the raindrops become too heavy for the cloud to hold on to, and they drop down together in a quick flash.

Effect of Cloudbursts:

Accompanying effect of Cloudbursts on terrain

• Landslides
• Mudflows
• Land caving

Flash floods – houses and establishments getting swept away and cave-ins lead to the deaths.

Blocking path of rivers that may lead to temporary damming and creation of a reservoir and its consequent collapse

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. It is the consequences of such heavy rain, especially in the hilly terrain, that causes death and destruction.

How cloudburst is different from rainfall?

1. A cloudburst is different from rain only in the amount of water that pours down on the earth.
2. The India Meteorological Department (IMD) labels rainfall over 100 mm per hour as cloudburst.
3. In simpler terms, if 10 centimetres rainfall is received at a station in one hour, the rain event is termed as cloudburst.
4. Usually small areas – anywhere  between 20-80 square kilometres are affected.