Sep. 24, 2001 A new computer model of the atmosphere can now actually pinpoint where global dust events come from, and can project where they're going. The model may help scientists better evaluate the impact of dust on human health, climate, ocean carbon cycles, ecosystems, and atmospheric chemistry.
Also, by seeing where dust originates and where it blows people with respiratory problems can get advanced warning of approaching dust clouds.
"The model is physically more realistic than previous ones," said Mian Chin, a co-author of the study and an Earth and atmospheric scientist at Georgia Tech and the Goddard Space Flight Center (GSFC) in Greenbelt, Md. "It is able to reproduce the short term day-to-day variations and long term inter-annual variations of dust concentrations and distributions that are measured from field experiments and observed from satellites."
Paul Ginoux, of Georgia Institute of Technology, is the lead author of the NASA funded study that appears in the September 16 issue of Journal of Geophysical Research - Atmospheres.
The new model determines sources of global dust by looking for areas with relatively low elevations that also have bare soil surfaces. The researchers found that during periods of high rainfall over the years, sediments accumulated in these topographically low areas, such as valleys or deserts, and these loose particles of dust were easily lifted into the atmosphere by winds.
The model, called the Georgia Tech/Goddard Global Ozone Chemistry Aerosol Radiation and Transport (GOCART) model, has been designed to trace many kinds of atmospheric gasses and particles. Along with dust, the model can simulate the paths of atmospheric sulfate, black carbon, organic carbon, sea-salt, radon, lead, and carbon monoxide. When it comes to dust, GOCART processes the paths of seven different particle sizes; noting that the smaller ones stay airborne and travel farther than the larger ones. The model uses outside meteorological data set from the Data Assimilation Office at GSFC; that data set is a combination of results from a general circulation model (GCM) and the actual observed meteorological readings of winds, temperature, pressure, water vapor and other weather factors.
The model has successfully identified the main source locations and strengths of dust include the Sahara, the semi-desert southern fringe of the Sahara called the Sahel that extends from Mauritania to Chad, the Indus Valley in India, the Taklimakan north of the Himalaya, the Gobi desert in Mongolia, the Lake Eyre basin in Australia, the Salton sea in southern California, the Altiplano and Patagonia in the Andes, and the Namibian source in southwest Africa.
The model finds that the North Atlantic Ocean, North America and Europe are largely affected by dust traveling from the Saharan desert and the sparsely vegetated Sahel region. This latter region was not accounted for in earlier global dust model studies, but new research has determined it is in fact a significant dust source, and it is now included in the new model.
The new computer simulations have already provided five-day dust forecasts, and will enable people with respiratory ailments to know when air quality might be affected by global dust and when to avoid outdoor activity. These forecasts would also be able to warn fisheries and tourism groups about the possibility of developing red tides, like those in the Gulf of Mexico.
A recent study found that carry disease-causing microbes hitch rides on dust particles flying across the world's oceans on atmospheric winds from the Sahara to American soil. Other studies have linked large blooms of toxic algae with Saharan dust that fertilizes the Gulf of Mexico with iron.
Scientifically, being able to forecast dust not only helps for climate prediction, but researchers can now better situate themselves during field campaigns to study the dust's effects.
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The above story is based on materials provided by NASA/Goddard Space Flight Center--Eos Project Science Office.
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