The sandstorms that can complicate life in Abu Dhabi are part of a complex weather pattern that also provides India with the monsoon rain essential to the crops that sustain one billion people, NYU Abu Dhabi researchers are learning. Olivier Pauluis, professor of mathematics and co-principal investigator at NYUAD's Center for Prototype Climate Modeling, explains how that works.
So what turns a sandstorm into a monsoon?
It's not that direct. Let's start on this side of the Indian Ocean. There's a strong westerly wind, known in Oman as the Gharbi — the Arabic word for "west" — that blows, starting in May or June, straight out into the Arabian Sea from the Rub al Khali, or Empty Quarter, in the Arabian Peninsula. That is the biggest sand desert on earth, so as you can imagine it's a big reservoir of very dry air that's being flushed out into the Arabian Sea.
And as it blows out towards Indian Ocean …
That's right. Some of it makes the sandstorms we experience in Abu Dhabi. There can be sandstorms in any month, of course, but the Gharbi is seasonal and that's when we often get big sandstorms.
On the other side of the Indian Ocean, meanwhile, the monsoon starts at the southern tip of India, and expands to the north by the end of June. We have found that the Gharbi typically starts around the time the Indian monsoon reaches its northernmost expansion.
So there's wet air and dry air?
The same wind that brings us sandstorms means that typically at the end of June there's a sudden drop in the precipitation and humidity in the air over the Arabian Sea. There is some variability from year to year, but it does seem that the dry air can shut down the monsoon. You have to understand that the monsoon is not just heavy rain all day every day, there are breaks in the season. And sometimes there are droughts, in 2002 and 2004 for example.
It's a very complicated system. At the NYUAD Center for Prototype Climate Modeling (CPCM) I'm working with three colleagues — Sandeep Sukurman, Ajaya Ravindran, and Sabin Purayil — to try to understand the connections better.
And this would have practical consequences?
If we could understand why the Gharbi is varying from year to year, then it might be quite helpful for India, where one billion people depend on rain from the monsoon. If we could give even two weeks of warning of a coming break in the monsoon, that could be important.
At the CPCM we are also trying to understand how this weather system will change as the planet heats up. Air can contain more moisture as it heats up, but dry air can become drier, too. The dynamics we see in the data may become more severe as the planet warms.