News - Mission Earth
Using the GLOBE Visualization system to look at aerosols
When making a GLOBE Clouds observation, one of the things to pay attention to is the shade of blue we see. But sometimes, the sky or parts of the sky do not even look blue! The color of the sky can give us clues about the presence of aerosols in the air. Aerosols are tiny solid and liquid particles suspended in the atmosphere. Windblown dust, sea salts, volcanic ash, smoke from wildfires, and pollution from factories are all examples of aerosols. These particles are important to scientists because they can affect climate, weather, and people's health. Most aerosols can affect climate. Some aerosols can warm the planet, like black carbon. Some aerosols also help cool Earth by helping form clouds. How? Aerosols can give water droplets something to cling to as the droplets form and gather in the air to make clouds. Aerosols can also impact human health. When we get aerosols in our lungs, they can cause asthma or other health problems. But scientists do not fully understand all of the ways that aerosols affect Earth's environment. To help them in their studies, scientists use satellites to map where there were large amounts of aerosol on a given day, or over a span of days. And this is where you come in! GLOBE observations can provide direct evidence of aerosols. IMPORTANT: Before making a dust observation, make sure you are safe in a sheltered place, without exposing yourself to the dust.
There are times when the quantity of aerosols is so high in your area that it obscures your view of the sky. When making GLOBE your observation, you should select "obscuration" whenever 25% or more of the sky is blocked by something like dust, ash, smoke, snow, etc.
The spring of 2025 has been an active period for dust storms over some regions of the United States. These storms have had major impacts in some areas. On May 16, 2025, a citizen scientist made a few GLOBE cloud observations within hours, which allowed us to see some incredible changes in the sky. That day, a dust storm grew near Bloomington, Illinois, progressing northeastward into the Chicago metropolitan area.
GLOBE Cloud photos submitted by a citizen scientist near Chicago, IL, USA (times in UTC)
Do you notice some dust on the bottom of the picture on the right?
The GLOBE Clouds team got excited to find this citizen scientist’s photos and decided to take a closer look. Did you know that you can overlay NASA satellite data on the GLOBE Visualization system? Let us look at an example, focusing again on that dust storm over Chicago while overlaying Terra satellite’s data.
After opening the GLOBE visualization system, select Atmosphere:
Then choose the Clouds protocol > Cloud photos and hit “Submit”:
There are different NASA satellite options you can apply. Let us choose “Aerosol Optical Depth (Terra)”, as shown below. Scientists use measurements from the MODIS sensor aboard NASA's Terra satellite to map the amount of aerosol that is in the air all over the world. Scientists call this measurement aerosol optical depth or thickness. It is a measure of how much light the airborne particles prevent from traveling through the atmosphere. Aerosols absorb and scatter incoming sunlight, thus reducing visibility and increasing optical depth. An optical depth of less than 0.1 indicates a crystal clear sky with maximum visibility, whereas a value of 1 indicates the presence of aerosols so dense that people would have difficulty seeing the Sun, even at mid-day!
Select “May 16, 2025”:
Zoom in or out the location you are interested in. For this example, we are zooming in the Chicago area.
GLOBE Visualization system, cloud photos on May 16, 2025, near Chicago, IL, USA
The legend on the lower-right corner indicates the presence of aerosols. Here you can learn more about how Aerosol Optical Thickness or Depth is measured.
If you see an impending dust storm and are able to capture it from a safe location, we would love to see those photos as well. Learn more about Dust Observations and how to use the GLOBE Observer app to submit your data.
If you are interested in learning more about using the GLOBE Visualization system, you can find very helpful tutorials here: Data Access, Analysis & Reporting Tutorials.
News origin: NASA Langley Research Center