28-06-2025
Knowledge Nugget: Why Cloudbursts and Flash Floods matter for your UPSC exam
Take a look at the essential concepts, terms, quotes, or phenomena every day and brush up on your knowledge. Here's your knowledge nugget for today.
(Relevance: In 2022, UPSC has asked a question: Explain the mechanism and occurrence of cloudbursts in the context of the Indian subcontinent. Discuss two recent examples. Questions related to climate events and climate-related reports have been UPSC favourites. In this regard, having a comprehensive understanding of this topic is important from the exam perspective.)
Three bodies were recovered in Kangra on Thursday (26th June), taking the toll from flash floods triggered by cloudbursts to five, said officials. At least four cloudburst incidents were reported in Banjar, Gadsa, Manikaran, and Sainj of Kullu district, officials said.
Given the heightened risk of floods, landslides, and cloudbursts following the active monsoon, the Himachal Pradesh Police Headquarters has issued an advisory.
1. A cloudburst is an extreme weather event. In simple words, it refers to intense rainfall occurring over a short duration within a small area. It is called an extreme weather event because the frequency of cloudbursts has increased due to global warming across the world.
2. The India Meteorological Department (IMD) defines it as unexpected precipitation exceeding 100mm (or 10 cm) per hour over a geographical region of approximately 20 to 30 square km. Significant amounts of rainfall such as this can result in floods.
(Note: Basically, all instances of cloudbursts involve heavy rain in a short period, but all instances of heavy rain in a short period are not cloudbursts if they do not fit this criterion.)
3. The formation of clouds and even cloudbursts occur suddenly. Doppler radars (used to determine the velocity of an object) can predict heavy rainfall events up to two hours in advance but they cannot detect the velocity if a mountain obstructs the signal. Also, cloudbursts are not confined to one place. The conditions that trigger cloudbursts can develop quickly in one location and then move to another, making it difficult for early prediction.
4. Excessive or continuous rainfall over a period of days, or during particular seasons, can lead to stagnation of water and cause flooding. Flash floods refer to such a situation, but occurring in a much shorter span of time, and are highly localised. It commonly happens more where rivers are narrow and steep, so they flow more quickly
5. In India, flash floods are often associated with cloudbursts – sudden, intense rainfall in a short period of time. Himalayan states further face the challenge of overflowing glacial lakes, formed due to the melting of glaciers, and their numbers have been increasing in the last few years.
To raise awareness about the significance of preserving glacier health in a warming world, the United Nations has declared 2025 as the International Year of Glaciers' Preservation.
6. Frequently, flash floods are accompanied by landslides, which are sudden movements of rock, boulders, earth or debris down a slope. It is common in mountainous terrains, where there are conditions created for it in terms of the soil, rock, geology and slope.
📍In the hill states like Himachal Pradesh, three main factors contribute to cloudbursts: first, the wind pattern; second, the height of the mountains; and third, the level of moisture and humidity in the air.
📍In the mountains, low-pressure areas form at the top, attracting clouds with significant force. Warm air creates thunderstorms. When air coming from the opposite direction collides with the mountain, it can result in a heavy downpour. This is why the height of the mountain matters in this scenario. The air cannot penetrate the mountain.
📍In these areas, sometimes saturated clouds ready to condense into rain cannot produce rain, due to the upward movement of the very warm current of air. Instead of falling downwards, raindrops are carried upwards by the air current. New drops are formed and existing raindrops increase in size. After a point, the raindrops become too heavy for the cloud to hold on to, and they drop down together in a quick flash.
1. According to the recently released State of Climate in Asia 2024 report, prepared by the World Meteorological Organization (WMO) in collaboration with regional and international meteorological organisations. The report highlighted how changes in key climate indicators such as surface temperature, glacier mass and sea level will have major repercussions for societies, economies and ecosystems in the region
2. According to the report, Asia experienced its warmest or second warmest year on record in 2024, with its average temperature 1.04 degree Celsius above the last 30-year average. Asia is warming up nearly twice as fast as the global average.
3. The impact of this high rate of warming in 2024 manifested through a range of extreme weather events such as 29 tropical cyclones, prolonged and intense heat waves and extreme rainfall events, including India.
4. In India, extreme heatwaves caused over 450 deaths across the country, the report said. During heatwaves in 2024, temperatures were in the range of 45-48 degree Celsius for sustained periods and touched a high of 50 degrees at some locations. The country also saw deadly lightning events, killing about 1,300 people, the report said.
5. Glaciers continued to lose mass, as per the report, with 23 out of 24 glaciers in the High Mountain Asia region of central-south Asia spanning Himalayas, Pamir mountains, Karakoram, Hindu Kush. The melting of glaciers affects sea level, regional water cycles and the occurrence of local hazards such as glacial lake outburst floods (GLOFs).
6. In terms of extent, marine heatwaves created a record in 2024, impacting an area of nearly 15 million square kilometres. The northern Indian Ocean, adjacent to Japan and the Yellow and East China seas faced particularly severe or extreme intensity of marine heatwaves.
Which of the following statements with regard to cloudburst is/are correct? (UPSC CDS 2017)
1. It is defined as sudden localized very heavy downpour with cloud thunder and lightning.
2. It mostly occurs in the hilly areas.
3. It results into very high intensity of rainfall, i.e., 250 mm-300 mm in a couple of hours.
4. It occurs only during the daytime.
Select the correct answer using the code given below.
(a) 1, 2, and 3
(b) 1, 3, and 4
(c) 2 and 3
(d) 2 only
(Source: Asia warming nearly twice global average, hit hard in 2024: WMO, Explained: What are cloudbursts, and why they occur more in places like Amarnath, Explained: What are flash floods and why they may increase in the next few years, Find out how a radar can help prevent damage caused by cloudburst)
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Khushboo Kumari is a Deputy Copy Editor with The Indian Express. She has done her graduation and post-graduation in History from the University of Delhi. At The Indian Express, she writes for the UPSC section. She holds experience in UPSC-related content development. You can contact her via email: ... Read More
