Aerosols — they are all around you and you are inhaling millions of them this very second. These minute solid and liquid particles suspended in the atmosphere, include dust, smoke, pollen, soot and even volcanic ash.
Earth-observing satellites use the Moderate Resolution Imaging Spectroradiometer (MODIS) to measure the aerosol optical thickness from hundreds of kilometers above the Earth. These measurements are based on the fact that aerosols change the reflection and absorption of visible and infrared light in the atmosphere. NASA has now released a vivid image that shows the aerosol flow across the face of Earth. According to NASA, “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.”
The image released on August 23, 2018, highlights the atmospheric aerosols on that day based on data from satellites Terra, Aqua, Aura and Suomi NPP.
- The blue colour indicates sea salt aerosols, which are natural aerosols carried into the atmosphere and come from sea spray.
- The red denotes black carbon particles. Wildfires, emissions from industries and automobiles are the common source.
- Dust particles are marked in purple.
According to NASA, “On that day, huge plumes of smoke drifted over North America and Africa, three different tropical cyclones churned in the Pacific Ocean, and large clouds of dust blew over deserts in Africa and Asia.”