What an Ozone Satellite Can Tell Us About Wildfires

This blog was written by Colin Seftor, who recently retired after more than 30 years supporting NASA Goddard Space Flight Center's Ozone Processing Team. Throughout his career, Colin relied on IDL^® to analyze satellite data, monitor atmospheric ozone, and, ultimately, uncover new ways to track volcanic eruptions, wildfire smoke, and other large-scale aerosol events.

This post is the latest in our IDL Fellows series, which supports passionate retired IDL users who want to continue their scientific work and share it with the broader community. IDL is a scientific programming language widely used for data analysis, visualization, and image processing across disciplines including Earth science, astronomy, remote sensing, and medical imaging. If you're retired, still using IDL, and interested in becoming an IDL Fellow, we'd love to hear from you. Reach out to learn more about the program and see if you qualify.

Most satellite instruments do exactly what they were designed to do. Sometimes, though, they surprise you.

During my 30-plus-years supporting NASA Goddard Space Flight Center’s Ozone Processing Team, my primary responsibility was monitoring the performance of satellite instruments that measure atmospheric ozone. Day after day, I relied on IDL to calibrate sensors, analyze enormous volumes of satellite data, and visualize what those instruments were seeing.

Over time, something unexpected emerged.

The same sensors we depend on to measure ozone turned out to be remarkably good at detecting something entirely different: volcanic ash, sulfur dioxide released during eruptions, smoke from massive wildfires, and dust carried thousands of miles from the Sahara Desert.

That discovery opened the door to studying atmospheric events far beyond the instruments’ original mission.

Seeing What the Eye Can’t

One of the most valuable products generated by these sensors is the Aerosol Index. Unlike true-color satellite imagery which can struggle to distinguish smoke or dust over bright surfaces such as clouds, snow, or ice, the AI highlights airborne particles regardless of what’s underneath.

That’s a significant advantage when you’re trying to understand how aerosols move through the environment. The image below illustrates the difference. The image on the left is a natural color view of the Northern Hemisphere from NOAA-20’s Visible Infrared Imaging Radiometric Suite (VIRS) on June 4th, 2025. Smoke from the Canadian wildfires and dust streaming from the west from the Sahara are visible, but some details are subtle.

The center image tells a different story. Using Aerosol Index data from the Ozone Mapping and Profiler Suite (OMPS), the extent of both smoke and dust becomes immediately apparent. Smoke blankets much of Canada before stretching across the Atlantic toward Europe, while Saharan dust spreads across northern Africa into the Atlantic Ocean.

Overlaying the Aerosol Index on the true-color image (right) combines the strength of both datasets, providing a clearer picture of where aerosols are, how extensive they are, and how they’re moving.

It’s important to note that the Aerosol Index detects aerosols, not their source. Additional analysis is required to determine whether a plume consists of smoke, dust, volcanic ash, or another type of airborne particle.