Cloudbursts

AUG 10

Preliminary   > Geography   >   Climatology   >   Climatology

Why in news?

  • Over 20 people have been killed in the destruction caused by cloudbursts and flash floods in different parts of Himachal Pradesh and Uttarakhand over the last three days.

About Cloudbursts:

  • A cloudburst is a localized but intense rainfall activity. However, not all instances of very heavy rainfall are cloudbursts.
  • A cloudburst has a very specific definition. Rainfall of 10 cm or more in an hour over a roughly 10 km x 10-km area is classified as a cloudburst event.
  • By this definition, 5 cm of rainfall in a half-hour period over the same area would also be categorized as a cloudburst.
  • Cloudbursts are common events, particularly during the monsoon months. Most of these happen in the Himalayan states where the local topology, wind systems, and temperature gradients between the lower and upper atmosphere facilitate the occurrence of such events.

Are Cloudbursts forecasted?

  • India Meteorological Department (IMD) forecasts rainfall events well in advance, but it does not predict the quantum of rainfall — in fact, no meteorological agency does.
  • The forecasts can be about light, heavy, or very heavy rainfall, but weather scientists do not predict exactly how much rain is likely to fall at any given place.
  • It requires a very dense network of weather instruments and computing capabilities that seem unfeasible with current technologies. As a result, specific cloudburst events cannot be forecasted.

Rising Cloudbursts incidents:

  • There is no long-term trend that suggests that cloudbursts are rising. However, incidents of extreme rainfall, as also other extreme weather events, are increasing — not just in India but across the world.
  • While the overall amount of rainfall in India has not changed substantially, an increasing proportion of the rainfall is happening in a short span of time. That means that the wet spells are very wet and are interspersed with prolonged dry spells even in the rainy season.
  • This kind of pattern, attributed to climate change, does suggest that cloudburst events might also be on the rise.

PRACTICE QUESTION:

Consider the following statements:

1. India Meteorological Department does not predict the quantum of rainfall

2. Rainfall of 10 cm or more in an hour over a roughly 10 km x 10-km area is classified as a cloudburst event

Which of the statements given above is/are correct?

(a) 1 only

(b) 2 only

(c) Both 1 and 2

(d) Neither 1 nor 2

Answer