As climate change disrupts monsoons, cloudbursts are hitting vulnerable mountain regions with deadly force.
Cloudbursts are causing chaos in mountainous parts of India and Pakistan, with tremendous amounts of rain falling in a short period of time over a concentrated area. The intense, sudden deluges have proved fatal in both countries. As many as 300 people died in one north-western Pakistani district, Buner, after a cloudburst. The strength and volume of rain triggered flash flooding, landslides and mudflows. Boulders from steep slopes came crashing down with the water to flatten homes and reduce villages to rubble. The northern Indian state of Uttarakhand had a cloudburst earlier this month. Local TV showed floodwaters surging down a mountain and crashing into Dharali, a Himalayan village. In 2013, more than 6,000 people died and 4,500 villages were affected when a similar cloudburst struck the state. What are cloudbursts? Cloudbursts are complex and extreme weather events that occur when a large volume of rain falls in a very short period, usually more than 100 millimetres within an hour over a localised area, around 30 square kilometres. They are sudden and violent, with devastating consequences and widespread destruction, and can be the equivalent of several hours of normal rainfall or longer. The event is the bursting of a cloud and the discharge of its contents at the same time, like a rain bomb. Several factors contribute to a cloudburst, including warm, moist air rising upward, high humidity, low pressure, instability and convective cloud formation. Moist air is forced to rise after encountering a hill or mountain. This rising air cools and condenses. Clouds that are large, dense and capable of heavy rainfall form. Hills or mountains act like barriers and often trap these clouds, so they cannot disperse or move easily. Strong upward currents keep moisture suspended inside the clouds, delaying rainfall. When the clouds cannot hold the accumulated moisture anymore, they burst and release it all at once.
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