The phenomenon of cloudbursts
- Category
Geography
- Published
2nd Aug, 2021
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Context
This year’s monsoon season has seen a spate of cloudbursts over the Western Himalayas and the west coast, revealing the deadly, unpredictable face of monsoon rains.
Background
What are cloudbursts?
- 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.
- Areas prone to cloudburst:Cloudbursts do occur at plains, however, mountainous regions are more prone to cloud bursts due to topography. They also occur in desert and in interior regions of continental landmasses.
Occurrence
- Generally cloudbursts are associated with thunderstorms. The air currents rushing upwards in a rainstorm hold up a large amount of water.
- Air current is air moving from an area of high pressure to an area of low pressure.
- If these currents suddenly cease, the entire amount of water descends on to a small area with catastrophic force all of a sudden and causes mass destruction.
- This is due to a rapid condensation of the clouds.
Naming game
- They are called 'bursts' probably because it was believed earlier that clouds were solid masses full of water.
- So, these violent storms were attributed to their bursting.
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Himalayan vulnerability to natural disasters
- The geography of a placemakes it vulnerable to cloudbursts—which are a convective phenomenon producing sudden high-intensity rainfall over a small area.
- Due to its topography, geology, propensity for tectonic activity and ecological fragility, the Himalayan region becomes prone to rapidly changing weather at micro-levels.
A 2017 study of cloudbursts in the Indian Himalayas noted that most of the events occurred in the months of July and August.
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How cloudburst is different from rainfall?
- A cloudburst is different from rain only in the amount of water that pours down on the earth.
- The India Meteorological Department (IMD) labels rainfall over 100 mm per hour as cloudburst.
- In simpler terms, if 10 centimetres rainfall is received at a station in one hour, the rain event is termed as cloudburst.
- Usually small areas – anywhere between 20-80 square kilometres are affected.
How anthropogenic factors are increasing the events?
- In recent years, the following anthropogenic factors have been implicated in extreme weather events in the Himalayas-
- Population
- Deforestation
- Land-use change
- Emissions due to urbanization
How climate change is adding to the issue?
- As per the Intergovernmental Panel on Climate Change (IPCC), glaciers in the Himalayas are receding faster than in any other mountain range.
- Glacial lakes formed by melting glaciers are constrained by ice dams.
- Since the Indian summer monsoon coincides with the melting of glaciers, ice dams are weakened by the additional stress of the monsoons and are prone to bursting.
- A flash flood in Kargil in May 2016 was attributed to this.
- 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.
- Several studies have shown that climate change will increase the frequency and intensity of cloudbursts in many cities across the globe.
- In May, 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.
- It added that 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.
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Given the current situation, the planet is surely going to witness cloudburst events in increased frequency in the future.