Scientists use data from NASA’s Total OzoneMapping Spectrometer (TOMS) to measure the relative amount ofaerosols—solid or liquid particles suspended in the atmosphere.Examples of such aerosols include dust, volcanic ash, and smoke. Thisfalse-color image is a map of where there are aerosols that absorbultraviolet (UV) radiation. Brown pixels show higher aerosolconcentrations, while yellow pixels show lower aerosol concentrations,and light blue regions indicate little or no aerosol.
This image, from April of 2000, shows dust blowing from the Sahara Desert intothe Atlantic Ocean, more dust from the Rub al Khali and Nafud deserts of theArabian Penninsula, and what may be smoke over northern India.
The TOMS aerosol index is related to aerosol optical depth, which, inturn, is a measure of how much light airborne particles prevent frompassing through a column of atmosphere. (Aerosols tend to absorb orreflect incoming sunlight, thus reducing visibility and increasingoptical depth and aerosol index.) For aerosol plumes at the most commonheight of 3 km, a TOMS aerosol index of less than 0.1 indicates acrystal clear sky with maximum visibility, whereas a value of 4indicates the presence of aerosols so dense you would have difficultyseeing the mid-day sun. (The relationship between aerosol index andoptical depth is dependent on altitude. Aerosols at low altitudes have alower TOMS aerosol index than an equivalent depth of aerosol at a higheraltitude).
Every day, TOMS measures the amount of UV radiation that is absorbedby the atmosphere and how much is reflected back up into space.Scientists use these daily measurements to estimate the location andamount aerosols present in the atmosphere over the entire Earth
TOMS aerosol index data and images.
References & Resources
Image data courtesy TOMS science team, NASA Goddard Space Flight Center
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