Scientists try to understand phenomenon that devastated Leh by lab simulation

A team of scientists in a government laboratory here has begun a process of trying to recreate the cloudburst that devastated Leh yesterday — on a supercomputer.

The cloudburst that triggered floods, brought down homes, and left over hundred people dead in Leh had too short a life for scientists to predict or even track it as it evolved and decayed.

So at the National Centre for Medium Range Weather Forecasting, near New Delhi, a team of atmospheric physicists has initiated an attempt to simulate the sequence of events that gave rise to the colossal cloud — believed to have a depth of about 15km — that collapsed in a rare cloudburst over arid Leh.

“Computer simulation is the best we can do now to try and understand how and why the cloudburst occurred,” a senior member of the team, who requested anonymity, said.

Weather observations from the past have indicated that cloudbursts usually occur during the monsoon —mainly in August — over the western Himalayan region.

“They appear to have something to do with leftover clouds that move towards the mountains,” the forecast centre researcher said. The source of a cloudburst which causes intense rainfall over a small area is typically a cloud that rises from about 500m above ground level to an altitude of 15km.

“It is like a giant reservoir of water in the atmosphere, all set for release when it gets the right trigger,” said Jivanprakash Kulkarni, a physicist at the Indian Institute of Tropical Meteorology, Pune.

Some scientists have speculated that night-time cooling may trigger condensation in the upper layers of the cloud that sets off a chain reaction that rapidly releases all accumulated water. “It has something to do with microphysics of clouds,” Kulkarni said.

A special weather radar that allows scientists to track the growth, moisture levels and other internal features of clouds could have helped them study cloudbursts in the western Himalayas — perhaps even watch them form and die in real time — but there is no such radar operational in that part of the country yet.

At the forecast centre near Delhi, the physics team will use an atmospheric model to mimic the conditions 24 hours prior to the cloudburst that occurred at about 30 minutes past midnight on Friday.

They will feed their supercomputer an enormous amount of data — temperature, wind and humidity, and solar radiation — and allow it to churn the numbers using a set of mathematical equations that dictate how the atmosphere will behave over time.

“We’re hoping our model will capture the cloudburst,” a team member said. “If it doesn’t show up, we’ll tweak the conditions — alter moisture levels or change wind flow patterns and see what happens in different conditions .”