The mineral properties of the aerosol particles and the wavelength distribution of incident light combine to determine whether a dust particle reflects radiation and cools the local atmosphere, absorbs radiation and warms the local atmosphere, or both. While scientists have a good handle on dust's primary effect of reflecting and cooling at the visible wavelengths, the smaller influence of absorbing and warming at the longer infrared wavelengths has remained more of an uncertainty and most climate models either underestimate it or do not include it at all.
When the field work concluded, Richard Hansell of the University of Maryland, College Park, and NASA's Goddard Space Flight Center, Greenbelt, Md., and colleagues combined data collected from the ground-based sensors with computer models to quantify the interaction of visible and infrared light energy.
The analysis showed that over half of dust's cooling effect is compensated for by its warming effect. The finding, published in the Journal of Geophysical Research, Atmospheres, could clarify scientists' understanding of how dust influences moisture fluctuations in the atmosphere and surface temperatures around the planet.
The dust dilemma
Dust is just one, but important, type of tiny airborne particle collectively known as aerosols. And while dust has a notable impact on health and visibility, it is also known to have an effect on climate. The question remains: How much of an effect?
As the 2007 assessment report by the United Nations' Intergovernmental Panel on Climate Change shows, the magnitude of aerosols' influence on climate is not well understood. That's where ground-based work like Hansell's can help. The team's interest was not in the global coverage of the dust events frequently observed by satellites but rather in the individual flecks of dust and their physical and chemical properties.
"Looking at dust from space, the spatial exten
|Contact: Kathryn Hansen|
NASA/Goddard Space Flight Center