Wildland fires can be a significant source of smoke that not only impairs our ability to enjoy clear vistas, but the gases and particulate matter it contains can be harmful to public health. When you see smoke in the sky it may be originating from a relatively local fire or a fire that is occurring several hundred miles away. The FIRMS SMOKE/AEROSOLS mode (in both FIRMS global and FIRMS US/Canada) can be useful for helping determine where the smoke is coming from. In this blog post, which is an update of one we published in 2021, we focus on the recent smoke plumes from the Canadian wildfires in June 2025, highlighting how FIRMS can be used to track the spread of smoke plumes.


Viewing smoke in FIRMS using corrected reflectance imagery

True color composite imagery acquired by instruments aboard several polar orbiting satellites including Terra MODIS, Aqua MODIS, S-NPP VIIRS,  NOAA-20 VIIRS and NOAA-21 VIIRS are provided as background “Dynamic Imagery” layers in FIRMS and FIRMS US/Canada Fire Maps. These layers display a "natural color image" of the Earth’s surface as it would look to the human eye from space. Consequently, it is easy to see smoke using this type of imagery in clear sky conditions. The time of observation for these polar orbiting satellites occurs at different times during the day, so they can be used to identify current sources of wildland fire smoke and visualize its transport across long distances. Explore the orbit tracks in the “Orbit Tracks and Overpass Times” layer grouping  to determine the daily overpass time for each satellite.


Viewing smoke in FIRMS using aerosol indices

Under the “Smoke and Aerosols” layer grouping, the standard Aerosol Index (AI) derived from S-NPP OMPS observations can also be used for identifying and tracking smoke as well as other aerosols. The OMPS Al, available in the “Overlays” layer grouping, detects and measures the density of smoke and suspended particles in the vertical air column in the atmosphere. Typical values of the AI range from 0 to 5 and higher values indicate dust storms or biomass burning smoke located in the lower troposphere (1-3 km). Values of 5.0 indicate heavy concentrations of aerosols that could reduce visibility or impact human health. For AI values significantly higher than 5 use the OMPS PyroCumuloNimbus, or pyroCb, AI layer. Larger pyroCb AI values between 5 and 10 usually indicate dense smoke from intensely burning fires that reach higher in the troposphere. Once the index gets above 10, the smoke has likely been produced from a pyroCb event, with dense smoke lofted into the upper troposphere and, often, into the stratosphere. More information on PyroCb events is available in this Earthdata blog

Wildland fire smoke visible in S-NPP VIIRS true color imagery acquired on June 1, 2025 (top – view in FIRMS t.ly/MLduo ). Active fire detections are displayed as red points. The aerosol index derived from S-NPP OMPS observations collected at the same time as the VIIRS imagery is provided for comparison (bottom – view in FIRMS  t.ly/y-UH2). Note: the aerosols detected over west Africa and westward to South America are associated with dust originating from the Sahara Desert. 

The aerosol index derived from S-NPP OMPS on June 7, 2025 shows smoke being transported to Europe (view in FIRMS  t.ly/4pdfz)


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