Cloudbursts in Himachal Pradesh

Why in News?

Recently, a cloudburst, leading to flash floods in Himachal Pradesh has killed many people and several missing.

About Cloud burst:

Cloud bursts are commonly used to designate a torrential downpour of rain which by its relative high intensity suggests bursting and discharge of a whole cloud in one go where more than 10 cm of rain falls in less than an hour over a small area, of about 10 square km.

ØThey often happen in mountainous areas, especially in the Himalayas.

Mechanism:

ØCloudbursts occur when strong upward currents of hot air prevent raindrops from falling, allowing them to grow larger while new smaller drops form below.

ØThis leads to a significant accumulation of water in the atmosphere, which is released abruptly when the upward currents weaken.

ØCloudbursts frequently occur in the hilly and mountainous areas of the Indian subcontinent, largely due to the region's complex topography, which facilitates orographic lifting.

ØOrographic lifting occurs when air rises and cools as it travels up the windward side of a mountain.

ØThis process enhances cloud development and rainfall as moist air ascends over the mountains, with monsoon dynamics and localised weather patterns further influencing these intense precipitation events.

Examples of Cloudbursts:

ØUttarakhand Cloudburst (July 2021

ØHimachal Pradesh Cloudburst (August 2020)

ØChennai floods(2015)

Consequences of Cloudbursts

ØFlash floods

ØLand slide

ØMud flows