How can we see air pollution with a camera?
Air pollution is a growing concern worldwide, affecting health, climate and weather systems. Scientists use special tools to measure tiny particles in the air, called aerosols, which can travel across continents and influence everything from human health to global temperatures. Dr John Barnes, a research scientist at NOAA’s Global Monitoring Laboratory in the US, has developed an innovative and affordable technique called Camera Lidar (CLidar) to detect these particles using a simple digital camera and a laser.
Talk like an … atmospheric scientist
Aerosol — a tiny particle or droplet suspended in the air, which can come from natural sources like dust and sea spray or human activities like pollution
Global warming — the increase in Earth’s average temperature due to greenhouse gases trapping heat in the atmosphere and other environmental factors
Laser — a tightly focused beam of light with many uses, including measuring distances and detecting particles
Lidar — a technology (laser radar) that uses laser pulses to measure distances or detect objects in the atmosphere
Pixel — the smallest unit of a digital image, representing a tiny part of the picture
Stratosphere — the second layer of Earth’s atmosphere, located above the troposphere and below the mesosphere. The stratosphere extends from approximately 7.5 miles (12 km) above the Earth’s surface to approximately 31 miles (50 km) above the Earth’s surface
Air pollution is a global problem that affects human health, weather patterns, and the climate. Tiny particles in the air, known as aerosols, play a complicated role: some reflect sunlight and cool the Earth, while others trap heat and contribute to global warming. These particles come from both natural sources, such as dust storms, sea spray and wildfire smoke, and human activities, such as urban pollution. To fully understand their impact, it is crucial to monitor their levels accurately. However, traditional methods of doing so are often expensive and complicated.
Dr John Barnes, a research scientist recently retired from NOAA’s Global Monitoring Laboratory, has developed a simpler and more affordable way to measure aerosols. His technique, called Camera Lidar (CLidar), uses a laser and a digital camera to track aerosol levels in the atmosphere. By making air quality monitoring more accessible, his work could help scientists worldwide better understand pollution, climate change and environmental health.
Why do we need to measure aerosols?
Aerosols can travel vast distances and impact the environment far from their sources. For example, smoke from wildfires can drift thousands of miles, and volcanic eruptions can send particles high into the atmosphere, affecting global temperatures. “In 1991, the explosive volcanic eruption of Mount Pinatubo in the Philippines put gases high into the stratosphere which formed aerosol particles,” explains John. “Once in the stratosphere, the particles spread all over the world. The particles cooled the Earth in the following year by reflecting sunlight back into space.” Scientists are now exploring whether injecting aerosols into the atmosphere could slow global warming, but this idea is still highly debated.
How are aerosols traditionally measured?
Scientists use different methods to measure aerosols, often by pulling air through instruments that analyse the size, shape and composition of particles. While these tools provide valuable data, they only measure air at ground level. “Many times, we want to know what is above us,” says John. “Flying planes or balloons with instruments is expensive, so laser radars (lidars) are often used.”
Lidar works by firing a laser pulse into the sky. As the light hits aerosols in the atmosphere, some of it bounces back and is detected by a telescope. The time it takes for the light to return reveals the height of the particles. While effective, traditional lidar systems are expensive, complex, and require advanced technology to process signals travelling at the speed of light.
How does the Camera Lidar (CLidar) technique work?
CLidar is a clever and simple way to measure aerosols. It works by using a powerful laser pointed straight up into the sky. When the laser beam passes through the atmosphere, it scatters light off any aerosols in the air – similar to how dust sparkles when caught in a beam of sunlight. The more aerosols there are, the brighter the laser beam appears. “For the CLidar, I point a laser (that is much brighter than a laser pointer) straight up and take a picture with a digital camera about 100 metres away,” explains John. The camera takes high-resolution pictures of the laser beam from the ground up to very high up in the atmosphere. By analysing the brightness of each pixel in the laser beam in these images, John can calculate the amount of aerosols at different heights, reaching up to 20 km or higher above the ground.
One major advantage of CLidar is its ability to measure aerosols all the way down to the ground, unlike traditional lidar systems that struggle near the Earth’s surface. “I’ve seen thin aerosol layers that nobody knew were there,” says John. “The measurements near the ground can also be compared with instruments that sample aerosols directly by pulling air into them.” The CLidar equipment is also portable and affordable, allowing scientists to take measurements from different locations easily.
What’s next for CLidar?
Air pollution is a serious issue worldwide, particularly in developing countries where monitoring equipment is often expensive and difficult to access. “Since the CLidar technique is relatively simple, inexpensive, and provides good data, I would like to see it used widely,” says John. “The lasers and cameras I use have become cheaper and better, so I think the CLidar will also improve.”
John is continually working to improve the CLidar technique. His next step is to use two cameras at different angles to observe the same section of the atmosphere. This could help measure the size of aerosol particles more accurately, providing valuable insights into their sources and effects. “I also hope to use different laser wavelengths (colours) to get more information,” says John. With these advancements, CLidar could become an even more powerful tool for monitoring air quality, helping scientists worldwide to better understand and address environmental challenges.
Dr John Barnes
National Oceanic and Atmospheric Administration Global Monitoring Laboratory, Boulder, Colorado USA (retired)
BJE Environmental Optics LLC, USA
Fields of research: Atmospheric physics, aerosols, environmental optics, lidar, ozone
Research project: Using the Camera Lidar (CLidar) technique to monitor aerosol levels in the atmosphere
Funder: US National Oceanic and Atmospheric Administration (NOAA) Small Business Innovation Research (SBIR) 2020-2023
Reference
https://doi.org/10.33424/FUTURUM574
John at the Mauna Loa Observatory, Hawaii
© John Barnes
© Mauricio Bridgewater
About atmospheric science
Atmospheric science is the study of the Earth’s atmosphere, focusing on weather patterns, climate and air quality. The field combines physics, chemistry, biology and engineering to better understand the interactions between the atmosphere, oceans, land and polar regions. Atmospheric scientists investigate phenomena that shape the environment, from the immediate weather to the long-term impacts of climate change.
One of the most rewarding aspects of atmospheric science is the ability to design and build instruments that address critical scientific questions and generate valuable data used by the wider research community. “In some cases, I was able to measure a fundamental quantity that other people would use for their research,” says John. “It is very satisfying to see my results referenced in other people’s scientific papers.”
Atmospheric scientists face a variety of challenges, especially when conducting research in remote locations. “I have been up to the Arctic twice; to Barrow, Alaska (now called Utqiagvik) and to Ny-Ålesund in Svalbard, Norway,” says John. “At Utqiagvik, the wind was really strong, which made the wind chill -51 °C (-59.8 °F).” In such extreme conditions, collecting data can be difficult and may require scientists to overcome obstacles in setting up equipment, as well as handling unique environmental risks, like polar bears in the Arctic. However, these challenges also provide opportunities to make significant contributions to our understanding of atmospheric processes.
The field of atmospheric science continues to evolve, with research opportunities emerging in areas such as air quality monitoring, climate change, and the interaction between the atmosphere and other Earth systems. Tools such as CLidar offer promising advancements by making it easier and more affordable to measure aerosol levels in the atmosphere. “Climate change isn’t going away anytime soon,” says John. “As each month goes by, we find out a little more about how our atmosphere, oceans, land and polar regions work together in a very complicated system.”
Pathway from school to atmospheric science
“Atmospheric science uses physics and math but also many other areas, including chemistry, biology, geography, computer science and fields of engineering,” explains John. “Deciding whether you like the math-modelling-theory side, or the experiment-measuring-observing side, can be just as important as the area to study.”
At university level, you can pursue a degree in atmospheric science, meteorology or geophysics. Some universities also offer specialised programmes in climate science, environmental science and oceanography, which may include atmospheric science components. “There are many universities that offer majors in atmospheric science, and many gives tours so you can learn more about their courses,” says John.
Explore careers in atmospheric science
Valuable resources include the US National Oceanic and Atmospheric Administration, the National Aeronautics and Space Administration, the Environmental Protection Agency, and the Department of Energy, all of which provide educational materials and career information.
For hands-on experience, outreach programmes and internships can be a great way to get involved. The NOAA Global Monitoring Laboratory offers educational resources online. “If you happen to be on The Big Island of Hawaii, you may be able to tour the NOAA Mauna Loa Observatory,” says John. “Tours have been suspended since Mauna Loa erupted in 2022 and lava covered the road, but they will restart one day, hopefully soon!”
Meet John
What inspired you to become an atmospheric scientist?
I was in graduate school when the ozone hole over the South Pole was discovered. My fellow graduate student, Dave Hanson, did some crucial measurements to explain what was happening. It was exciting to see that piece of the puzzle discovered. A meeting with most of the nations of the world followed where they decided to phase out CFCs (chlorofluorocarbons) and other chemicals that are depleting the natural ozone layer up in the stratosphere. Doing research related to pressing environmental issues was certainly inspirational. Besides, it was fun working with lasers, mass spectrometers, ozone generators and advanced math.
What experiences have shaped your career?
In an earlier engineering job, I was told by three very knowledgeable people that the problem I was working on had to be solved approximately, with a computer calculation. After a couple of tries, I developed a theory with very elegant, simple functions as solutions, which gave much more insight into the behaviour of the engineering process.
With the CLidar, I thought the first data I got didn’t make sense. A year later, I tried again with better equipment and got the same answer. I left a plot of the data on my desk and for a month, would look at it and wonder what was wrong. I finally realised that I was thinking about it in the wrong way. A week later, I had a very nice, new theory that explained the data perfectly.
What are your proudest career achievements so far?
I measured the amount of ultraviolet light that ozone absorbs at a precise wavelength, which is used in many parts of ozone research. About 20 other groups also measured the quantity and after 40 years, it appears my measurement is the best. When I got to the NOAA Mauna Loa Observatory, my first job was to build a new lidar to replace the old system that had run for 20 years but was out-of-date. I continued the lidar records with weekly trips up the mountain (well over a thousand), and we have now reached 50 years of recording the aerosol altitude profiles.
What are your aims for the future?
I will continue helping groups to use the CLidar for aerosol observations and continue trying new ideas to improve the technique. I also have a related particle instrument, the Imaging Polar Nephelometer (Patent 8,531,516), that I want to develop.
John’s top tips
One very nice thing about the atmosphere is that it’s literally all around us! You can learn a lot by being observant and comparing websites like https://www.airnow.gov/about-airnow/ to your local conditions.
There is also a growing number of inexpensive instruments to measure aerosols, gases and meteorological parameters. You can even make measurements in your community. I wanted to test some little particle counters, so I plugged them into a battery pack, put them in a backpack, and rode around town on my bicycle!
Do you have a question for John?
Write it in the comments box below and John will get back to you. (Remember, researchers are very busy people, so you may have to wait a few days.)
Read about how ecotoxicologists are investigating the impact of toxic pollutants on aquatic life:
www.futurumcareers.com/beyond-the-spill-the-hidden-effects-of-crude-oil-pollutants-on-fish-behaviour
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