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Global dust-cam


NASA now provides movies online showing the movement of dust around the globe.


NASA now has a web page with daily updates on the movement of airborne dust, smoke, and other particulates around the globe. The maps and movies provided use data from NASA's Total Ozone Mapping Spectrometer (TOMS) used mainly to monitor the ozone layer.

Because dust particles are so small - often less than 0.002 mm across - they can remain aloft for days as they ride global rivers of air. Larger sand grains don't get airborne as often or for as long, but can be pushed along the ground by wind or washed away by water erosion.

This constant reshuffling of the world's sand and dust ties the continents together. In nature there are no political boundaries. Airborne microbes and pollen in Florida or Brazil might have come from Africa. Mineral dust in the soils of India could have blown from Iran.

In fact, over vast stretches of geological time, the action of wind thoroughly mixes and re-mixes the world's dust. So the soil in your own backyard might contain grains of dust from all over the globe.

An estimated 13 million tonnes of dust is transferred each year drifting from Africa to the Northeastern Amazon Basin alone.

"In some cases, such as in the Caribbean islands, much of the dust in the top soil is from Africa," says Jay Herman, principle scientist for aerosol detection by TOMS at NASA's Goddard Space Flight Center. "Over generations, lots of it piles up there. The top soil has been analysed on these islands, and it's definitely of African origin."

Northern spring also brings massive dust clouds blowing east over the Pacific Ocean from China and Mongolia. The largest Asian dust cloud on record blew all the way across North America earlier this year, travelling as far east as the mid-Atlantic Ocean before finally disappearing from view.



The TOMS instrument also detects volcanic ash, pollutants, smoke, ozone concentrations and ultraviolet light intensities.

To detect aerosols, the TOMS instrument records two particular wavelengths of ultraviolet (UV) light: 331 nanometres and 360 nanometres. Some of the UV light reflecting from Earth is absorbed by the dust and other aerosols. Clouds reflect both wavelengths while aerosols cause absorption of the shorter wavelength more than the longer one. This difference allows scientists to distinguish aerosols from clouds.