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This image shows the annual mean aerosol optical depth for 2006.
Aerosols are tiny particles, such as soot or dust, suspended in the Earth's atmosphere. In addition to their air-quality impacts, aerosols can interfere with sunlight reaching the planet's surface. Scientists often talk about aerosols in terms of their optical depth, which indicates how much incoming sunlight aerosols prevent from reaching the Earth's surface. The Moderate Resolution Imaging Spectroradiometer (MODIS) flying on NASA's Terra and Aqua satellites can detect aerosols. This image shows the annual mean aerosol optical depth for 2006, based on daily measurements made by MODIS. White represents little or no aerosol interference with sunlight, and dark orange indicates considerable interference. Areas where data could not be collected appear in gray.
Credit: NASA image by Reto Stockli, Earth Observatory; image interpretation by Lorraine Remer
Images credited to the National Science Foundation, a federal agency, are in the public domain. The images were created by employees of the United States Government as part of their official duties or prepared by contractors as "works for hire" for NSF. You may freely use NSF-credited images and, at your discretion, credit NSF with a "Courtesy: National Science Foundation" notation.
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