Death toll rises to 11, searches on for over 40 missing

Death toll rises to 11, searches on for over 40 missing

Subject: Geography

Sec: Climatology

Context:

Over 40 people are still missing after a series of cloudbursts occurred in Kullu’s Nirmand, Sainj and Malana, Mandi’s Padhar and Shimla’s Rampur subdivision on the night of July 31 and wreaked havoc.

Cloudburst:

• According to the Indian Meteorological Department (IMD),cloudbursts are sudden, heavy rainstorms where more than 10 cm of rain falls in less than an hour over a small area, of about 10 square km. They often happen in mountainous areas, especially in the
• In the Indian Subcontinent, it generally occurs when a monsoon cloud drifts northwards, from the Bay of Bengal or the Arabian Sea across the plains then on to the Himalaya which sometimes brings 75 mm of rain per hour.
• Causes:
  • Cloudbursts occur when strong upward currents of hot air prevent raindrops from falling, allowing them to grow larger while new smaller drops form below.
  • This leads to a significant accumulation of water in the atmosphere, which is released abruptly when the upward currents weaken.
  • Cloudbursts frequently occur in the hilly and mountainous areas of the Indian subcontinent, largely due to the region’s complex topography, which facilitates orographic lifting.
    • Orographic lifting occurs when air rises and cools as it travels up the windward side of a mountain.
    • This 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.
  • Cloudburst are Different from Rainfall:
    • Rain is condensed water falling from a cloud while cloudburst is a sudden heavy rainstorm.
    • Rain over 10 cm per hour is categorised as a cloudburst.
    • The cloudburst is a natural phenomenon, but occurs quite unexpectedly, very abruptly, and rather drenching.
  • Prediction:
    • There is no satisfactory technique for anticipating the occurrence of cloud bursts through satellites and ground monitoring stations because they develop over a small area and for a period of time.
    • A very fine net work of radars is required to be able to detect the likelihood of a cloud burst and this would be expensive.
    • Much of the damage can be avoided by way of identifying the areas and the meteorological situations that favour the occurrence of cloud bursts.
  • Examples of Cloudbursts:
    • Uttarakhand Cloudburst (July 2021):Devastating cloudbursts in Chamoli, Uttarkashi, and Pithoragarh caused flash floods, landslides, and extensive damage to infrastructure and lives.
    • Himachal Pradesh Cloudburst (August 2020):Cloudbursts in Kullu, Lahaul-Spiti, and Kinnaur triggered landslides and flash floods, damaging roads, bridges, and houses.