Why cloudbursts could become more frequent

Why cloudbursts could become more frequent

Subject: Geography

In news:  On July 28, at least seven people were killed, 17 injured and over 35 missing after a cloudburst hit a remote village of Jammu and Kashmir. Recently, cloudbursts have been reported from several places in J&K, Union Territory of Ladakh, Uttarakhand and Himachal Pradesh. A 2017 study of cloudbursts in the Indian Himalayas noted that most of the events occurred in the months of July and August.

What is a cloudburst?

• Cloudbursts are short-duration, intense rainfall events over a small area.
• According to the India Meteorological Department (IMD), it is a weather phenomenon with unexpected precipitation exceeding 100mm/h over a geographical region of approximately 20-30 square km.
• The cloudburst is a localised weather phenomena which leads to flash floods/ landslides, house collapse, dislocation of traffic and human casualties on a large scale.

Meteorological factors behind the cloudburst:

• Generally cloudbursts are associated with thunderstorms.
• A study published last year studied the meteorological factors behind the cloudburst over the Kedarnath region. They analysed atmospheric pressure, atmospheric temperature, rainfall, cloud water content, cloud fraction, cloud particle radius, cloud mixing ratio, total cloud cover, wind speed, wind direction, and relative humidity during the cloudburst, before as well as after the cloudburst.
• During the cloudburst, the relative humidity and cloud cover was at the maximum level with low temperature and slow winds.

Examples of cloudburst:

• 2010 Ladakh Floods: A major cloudburst and heavy rainfall triggered mudslides, flash floods and debris flow in Jammu and Kashmir’s Ladakh. 71 towns and villages in Leh were affected in the region and at least 255 people died.
• 2013 Uttarakhand Floods: The multi-day cloudburst in the hill state of Uttarakhand triggered flash floods and massive landslides.

Climate Change and cloudbursts:

• Several studies have shown that climate change will increase the frequency and intensity of cloudbursts in many cities across the globe.
• The World Meteorological Organization noted that there is about a 40% chance of the annual average global temperature temporarily reaching 1.5°C above the pre-industrial level in at least one of the next five years.
• There is a 90% likelihood of at least one year between 2021 and 2025 becoming the warmest on record and dislodge 2016 from the top rank.
• As temperatures increase the atmosphere can hold more and more moisture and this moisture comes down as a short very intense rainfall for a short duration probably half an hour or one hour resulting in flash floods in the mountainous areas and urban floods in the cities.

Areas Prone to cloudburst:

• A Cloudburst usually occurs in high-altitude areas due to the formation of a low-pressure area on the top of a mountain.
• They occur most often in desert and mountainous regions, and in interior regions of continental landmasses. 
• The topographical conditions like steep hills favour the formation of these clouds in the mountainous regions.
• The Chota Nagpur plateau spread across north Odisha, West Bengal and Jharkhand is the world’s most vulnerable spot for formation of severest thunderstorms.
• Cloudburst can occur not only in the monsoon seasons but also during March to May which is known for severe convective weather activities.

Prediction:

• The large-scale features, which are conducive for occurrence of severe thunderstorms associated with cloudburst, are predictable two to three days in advance.
• However, the specific location and time of cloudburst can be predicted in NOWCAST mode only, i.e. a few hours in advance, when the genesis of a thunderstorm has already commenced.
• To detect these sudden developments, a Doppler Weather Radar (DWR), a powerful tool for time and location specific prediction of cloudburst, can be deployed a few hours in advance. Coupled with satellite imagery this can prove to be useful inputs for extrapolation of cloudbursts anywhere in India.