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Earth’s atmosphere contains tiny liquid and solid particles called aerosols. Natural aerosol particles, such as dust and sea salt, tend to be larger than human-produced aerosols, such as particle pollution from burning fossil fuels. These aerosol size maps are based on data from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite. Green areas show where the aerosols that were present were mostly larger particles. Red areas show where aerosols consisted mostly of small particles. Yellow areas show plumes with an even mix of small and large particles. Gray shows where the sensor did not collect data.
The aerosol maps show average monthly aerosol amounts around the world based on observations from the MODIS sensor on NASA's Terra satellite. Satellite measurements of aerosols, called aerosol optical thickness, are based on the fact that the particles change the way the atmosphere reflects and absorbs visible and infrared light. An optical thickness of less than 0.1 (palest yellow) indicates a crystal clear sky with maximum visibility, whereas a value of 1 (reddish brown) indicates very hazy conditions.
View, download, or analyze more of these data from NASA Earth Observations (NEO):
Aerosol Optical Depth