NewsApril 1, 2014

Spectacular Satellite Image: Sahara Dust Sweeps Over UK

By Andrea Thompson

Follow @AndreaTWeather

Folks in the UK may have noticed a layer of grime on their cars at the end of March, the sort you might find after a windy day parked by the beach. But this dust didn’t have anything to do with taking a holiday – it blew in all the way from the Sahara Desert.

Dust makes the 2,000 mile trek from the Sahara to the UK several times a year. Malcolm Brooks, a scientist with the Met Office who studies dust storms, said that as air heats up over the Sahara, it creates convection that starts the winds blowing.

When winds are at least 20 mph, they can kick up sand from the desert, which in turn stirs up smaller bits of dust. That dust is light enough that the winds pick it up and loft it high into the atmosphere.RELATEDDusty Springs in Asia, Africa Can Increase Snow in Calif.
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The visualization of false-color satellite data above shows the origins of the dust that recently coated British cars. At the beginning of the video is a flash of pink over northwest Africa – “that little flash of pink is where the dust have been lifted in the Sahara,” Brooks said.

The dust reaching the UK – usually by being pulled into the air trailing behind a storm tracking to the north of the British Isles – isn’t anything like the haboobs that sweep across places like the Middle East and the U.S. Southwest.

While this type of dust doesn’t cause as much widespread disruption (or apocalyptic photographs) as its Middle Eastern and Southwestern brethren, it can cause beautiful sunsets.

The Sahara’s dust can also blow clear across the Atlantic Ocean to the U.S. East Coast. Its path takes it straight over one of the prime areas for development of Atlantic hurricanes, though what impact the dust has on the formation of these storms is one of intense scientific debate and research.

Dust could dampen storm formation by blocking out sunlight, which generally helps increase ocean temperatures. That warm water, in turn, is the fuel that drives a tropical cyclone’s convection engine. But dust can also act as a surface for water to grab onto, potentially helping to form clouds and raindrops, though exactly how this affects storm formation is unclear.

While precipitation rates in the Sahara Desert aren’t expected to change much with global warming, other areas, such as the U.S. Southwest, are expected to become more arid, which could increase dust storms there, according to the U.S. Geological Survey.

Changes in temperature and precipitation as well as land use in the Southwest are already covering downwind snowpack in the Rockies with in a coat of pink dust. A recent study found that snow is disappearing 6 weeks earlier in the Colorado Rockies now compared to the 1800s because that dust absorbs sunlight and melts the snow. That has reduced Colorado River runoff by 6 percent.

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