Cloudbursts, Climate Change, and the recent Amarnath tragedy

Gujarati

The Amarnath Yatra is being held after a hiatus of three years and the government authorities had estimated that this year, one would witness the biggest Yatra with an attendance of around six lakh pilgrims. Things were going smoothly till Friday afternoon (July 8, 2022) when heavy rainfall struck the area and the subsequent flash floods washed away 17 people to their death. According to a report on July 10, 44 people have been injured in the tragedy while many more are still missing. 

While the heavy rainfall that caused the flash floods at Amarnath in Jammu and Kashmir is being termed as a ‘cloudburst’ by many, the Indian Meteorological Department has however come forward now stating that what happened at Amarnath is not a cloudburst.

WHAT IS A CLOUDBURST AND WHAT IS NOT?

Many link the term ‘Cloudburst’ with some ‘bursting’ or ‘explosion’ but actually, it is nothing but extreme amount of rainfall in a short period over a comparatively smaller area. Cloudbursts take place when an extreme amount of precipitation occurs in a short period of time within a small geographical area. 

The India Meteorological Department (IMD) defines it as ‘unexpected precipitation exceeding 100mm (10cm) per hour over a geographical region of approximately 20 to 30 square km’. 

This points to the fact that all instances of heavy rainfall might not come under the category of ‘cloudburst’ if it does not fit in with the definition mentioned above. At the same time, the fact holds true that a particularly heavy rainfall event that might not get counted as a ‘cloudburst’ might be quite catastrophic. The recent Amarnath tragedy is perhaps the best example. 

WHAT HAPPENED AT AMARNATH?

According to IMD, what happened at Amarnath is highly localised heavy rainfall but not to the tune of getting counted as a ‘cloudburst’. As per reports, there was no rainfall at Amarnath from 8:30 am to 4:30 pm on the fateful day. After which, there was 31 mm of rainfall between 4:30pm and 5:30pm, meanwhile, between 5:30pm and 6:30pm there was 25 mm of rainfall and 19mm from 6.30pm to 7.30pm. These records show that there was no significant rainfall at Amarnath that day to be counted as a ‘cloudburst’ according to the IMD definition. Amarnath had received only 75mm of rainfall in 3 hours that day, much less than the IMD criteria of 100mm of rainfall in an hour. 

It is clear now from videos recorded by witnesses that a nearby stream suddenly brought down heavy rubble and a large quantity of water which point to the fact that some extreme rainfall event had taken place at the higher reaches of the mountains. 

Director, J&K Meteorological Centre, Srinagar talked about the probability of severe rainfall at higher altitudes, as a result of which water gushed down the steep slopes of the mountains. “Cloudburst, if any, might have occurred at an altitude higher than that of the cave shrine,’’ he said to The Indian Express. 

“The flash floods could have been triggered due to rainfall in the higher reaches of the mountains near the Amarnath cave shrine,” IMD Director General Mrutyunjay Mohapatra told PTI.

CLOUDBURSTS AND THE HIMALAYAS

While cloudbursts do occur in the plains, mountainous regions are more prone to them. In India, the Himalayas are particularly prone to cloudburst events and subsequent flash floods due to their typical orography (terrain and elevation).

According to a study published in 2017, Cloudbursts in Indian Himalayas: a review, “The Himalayan orography with its steep and unstable inclines forms a perfect platform for such a cloudburst event to lead to flash floods or landslides.”

While the Amarnath region itself received no ‘cloudburst type’ rainfall on that fateful day, the exact extremity of the rainfall in the interior and upper reaches of the Himalayas during that time period is not known. 

“Cloudbursts in and around the southern rim of the Indian Himalayas are elusive in terms of their position and time of occurrences. Most of the reported cloudbursts are in the interior of the Himalayas and hence their observation itself is limited,” the study further pointed out. 

Just like in the recent Amarnath tragedy, such ‘cloudburst’ events only get highlighted when the effect is felt in the downstream region. 

“Most of these events are reported once their effect in terms of loss to life and property is experienced in the downstream habitats. In addition, they are mostly associated with flash floods as an impact of the torrential precipitation,” the study also noted. 

MONSOON AND CLOUDBURSTS

The Indian monsoon season seems to have a direct connection with the cloudburst events in the Himalayas. Most of the cloudburst events occur during the monsoon season, mainly during the months of July and August (Bhan et al. 2004). According to Das et al. (2006) “cloudbursts in India occur when monsoon clouds associated with low-pressure area travel northward from the Bay of Bengal across the Ganges plains onto the Himalayas and burst in heavy downpours”

When moisture-rich air travels in an upward direction along the steep slopes in a mountainous region, it forms a vertical column of clouds called Cumulonimbus clouds. This upward movement is known as ‘orographic lift’ and the unstable clouds may lead to heavy rainfall over a small area, leading to what we call ‘cloudbursts’. 

CLIMATE CHANGE AND FREQUENT CLOUDBURSTS

With ‘Cloudbursts’ becoming more frequent nowadays, experts said that rising temperatures as a result of climate change could be a reason behind it. It is well-known that a warmer atmosphere has the capacity to hold more moisture and the Indian Ocean is one of the most rapidly warming oceans in the world at present. 

“These strong monsoon winds in the Bay of Bengal can now carry much more moisture than ever before, in response to global warming,” Roxy Mathew Koll, who is a climate scientist at the Indian Institute of Tropical Meteorology said to the magazine Down to Earth. “The volume of atmospheric moisture increases with rising temperature because warmer air holds more moisture for longer.”

According to an analysis by Down To Earth based on media reports, at least 26 cloudbursts occurred in the Himalayan region between January-July 29, 2021. The magazine however clarifies that the IMD did not report any of these incidents as cloudbursts as they didn’t fit with the minimum threshold of IMD (100mm of rainfall in an hour) which the magazine regarded as quite high. 

Also, the fact that the temperature rise in the Himalayan region is higher than the global increase in temperatures might be another contributing factor to a rise in the frequency of cloudburst-like events in the region. 

According to a 2019 study, Unravelling Climate Change in the Hindu Kush Himalaya: Rapid Warming in the Mountains and Increasing Extremes, “In the future, even if global warming is kept to 1.5 °C, warming in the Hindu Kush Himalaya (HKH) region will likely be at least 0.3 °C higher, and in the northwest Himalaya and Karakoram at least 0.7 °C higher”. The study also notes that, “For the past five to six decades, the HKH have shown a rising trend of extreme warm events; a falling trend of extreme cold events.”

The Intergovernmental Panel on Climate Change says glaciers in the Himalayas are receding fast because of rapid melting due to rising temperatures. “Extreme precipitation is projected to increase in major mountainous regions with potential cascading consequences of floods, landslides and lake outbursts in all scenarios,” stated the Sixth Assessment Report of the IPCC. 

HERE’S WHAT EXPERTS SAY

We reached out to our in-house expert, climate scientist, Dr Partha J Das. Here’s what he said on the topic:

Cloud bursts are crucial hydrometeorological phenomena in the entire Himalayan region (both western and eastern) mainly because in most cases they led to catastrophic flash floods. The complicated mechanism of formation of intense moisture bearing clouds and the extremely rapid rate of condensation under a set of conducive atmospheric conditions is difficult to predict. However, it is possible to monitor synoptic situations of areas having past record of experiencing cloud bursts using advanced technologies like the Doppler Weather Radar (DWR).

The GoI (mainly IMD and NDMA) could do well to establish state of the art high density hydro-meteorological gauging stations including DWR in all important pilgrimage routes and areas in mountainous regions and provide round the clock monitoring of hazards like land slide, heavy rainfall including cloud burst and potential landslide lake outburst floods and glacial lake outburst floods. Local people, pilgrims, government, defence forces and other users of such routes and areas should be alerted with early warning of the probability of such hazards to the maximum possible accuracy so that they can make proper decision about human movements and required restrictions to avoid accidents, loss of lives and minimise disaster risk.

A thorough scientific investigation of all such incidents of heavy rainfall induced flash floods including the known cases of cloud bursts and their impact should be done regularly by concerned state and central government agencies. This will help in gathering more information and contribute to knowledge building about these important natural phenomena.

The possibility of cloud bursts being intensified and frequented due to global warming and consequent changes in global and regional climates is scientifically highly plausible. But since cloud bursts are difficult to identify when under formation, or to predict, we do not have enough information or a long-term database on this class of events. Hence it may not be apt to say conclusively that cloud bursts are increasing in number in the Himalayas. However, since research indicate increase in events of heavy rainfall as a result of climate change, it is likely that cloud bursts could also be happening with more intensity and frequency due to climate change.