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	Coverage of this dataset spans November 2000 to February 2006.
	The animation features of the Earth Observatory are currently unavailable. We apologize for the inconvenience. To view the full temporal span of this dataset, please view the Aerosol Optical Depth monthly holdings.

Product description: Scientists use data from the MODIS sensor to measure the relative amount of aerosols -- solid or liquid particles suspended in the atmosphere. Examples of such aerosols include dust, sea salts, volcanic ash, and smoke. This false-color image is a map of where there are aerosols that reflect visible and near infrared radiation. Dark brown pixels show high aerosol concentrations, while tan pixels show lower aerosol concentrations, and light blue regions indicate little or no aerosol. Grey indicates regions where no data are available. The MODIS aerosol optical depth product is a measure of how much light airborne particles prevent from passing through a column of atmosphere. Aerosols tend to absorb or reflect incoming sunlight, thus reducing visibility and increasing optical depth. An optical depth of less than 0.1 indicates a crystal clear sky with maximum visibility, whereas a value of 4 indicates the presence of aerosols so dense you would have difficulty seeing the sun at mid-day! Aerosols are scientifically important because they represent an area of great uncertainty in efforts to understand and predict global climate change. Moreover, they can influence rainfall patterns as well as cause respiratory problems in humans and animals. Every day over the entire planet, MODIS measures the amount of visible and infrared light that is absorbed within the atmosphere and how much is reflected back up into space. Scientists use these measurements to estimate the location and amount aerosols present in the atmosphere. The image above represents the average aerosol optical depth over the Earth for the month indicated. Image courtesy Reto Stockli, Earth Observatory, based upon data provided by the MODIS Science Team, NASA Goddard Space Flight Center

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