The weather experiment that really flooded Dubai

By Jack Marley, The Conversation

A reckless experiment in Earth’s atmosphere caused a desert metropolis to flood.

That was the story last week when more than a year’s worth of rain fell in a day on the Arabian Peninsula, one of the world’s driest regions. Desert cities like Dubai in the United Arab Emirates (UAE) suffered floods that submerged motorways and airport runways. Across UAE and Oman, 21 people lost their lives.

The heavy rain of Tuesday April 16 was initially blamed on “cloud seeding”: a method of stimulating precipitation by injecting clouds with tiny particles that moisture can attach to – those droplets then merge and multiply. As the waters receded, however, a more disturbing explanation emerged.

Richard Washington, a professor of climate science at the University of Oxford, has seen the inside of a storm. To confirm if cloud seeding really could breed record-breaking rain, he once boarded an aeroplane bound for a thundercloud over the South Africa-Mozambique border.

“Our mission was to fly through the most active part of the storm, measure it, fly through again while dumping a bin load of dry ice, turn hard and fly through for a final measurement,” he says.

“Apart from the fun of flying through the core of a thunderstorm in a Learjet, I didn’t think much about the time I was lucky enough to be part of that project. Until I heard about the recent freak storm in Dubai.”

What caused the flood?

There are no two identical clouds with which to compare the outcome of seeding, Washington says, so it’s impossible to prove if this technique can change the outcome of a single storm. But by flying a lot of missions, half with cloud seeding and half without, and measuring rainfall between the two, meteorologists eventually showed that cloud seeding did modify rain rates in some storms.

That’s not what caused Dubai’s floods though.

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