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TOMS Aerosol Index
This page contains archived content and is no longer being updated. At the time of publication, it represented the best available science. However, more recent observations and studies may have rendered some content obsolete.
Scientists use data from NASAs Total Ozone
Mapping Spectrometer (TOMS) to measure the relative amount of
aerosolssolid or liquid particles suspended in the atmosphere.
Examples of such aerosols include dust, volcanic ash, and smoke. This
false-color image is a map of where there are aerosols that absorb
ultraviolet (UV) radiation. Brown pixels show higher aerosol
concentrations, 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 into
the Atlantic Ocean, more dust from the Rub al Khali and Nafud deserts of the
Arabian Penninsula, and what may be smoke over northern India.
The TOMS aerosol index is related to aerosol optical depth, which, in
turn, 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 and aerosol index.) For aerosol plumes at the most common
height of 3 km, a TOMS aerosol index 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 mid-day sun. (The relationship between aerosol index and
optical depth is dependent on altitude. Aerosols at low altitudes have a
lower TOMS aerosol index than an equivalent depth of aerosol at a higher
Every day, TOMS measures the amount of UV radiation that is absorbed
by the atmosphere and how much is reflected back up into space.
Scientists use these daily measurements to estimate the location and
amount aerosols present in the atmosphere over the entire Earth