Don’t blame Dubai’s freak rain on cloud seeding – the storm was far too big to be human-made

By Richard Washington, University of Oxford

Some years ago, I found myself making my way up the narrow stairs of a Learjet on a sultry runway in a deserted airport near the South Africa-Mozambique border. The humidity was there to taste – the air thick with it.

The weather radar was showing a fast-developing thundercloud. 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.

The inside of the Learjet resembled a food blender, so severe was the turbulence. Thousands of meters below, a smaller plane would be threading through the storm downdrafts measuring the rain. It isn’t something you do every day although the saucer-sized hail dents on the wings of the Learjet told of its many prior engagements.

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.

The project I was part of, neatly named Rain (Rain Augmentation in Nelspruit), was a cloud seeding experiment several years in the making. Cloud seeding involves adding tiny particles into a cloud in order to give moisture something to attach to and form droplets. Gradually those droplets merge and become heavy enough to fall as rain. In theory, the “seeeded” clouds will grow more droplets suitable for rain.

No one flight is proof of seeding having been effective. It can’t be. There is no identical cloud with which to compare the outcome of having seeded a particular cloud. It is therefore necessary to fly a lot of missions and to measure, but not seed, half of them thereby creating a data set for the experiment itself (seeded clouds) and the control (unseeded clouds).

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