LA’s carbon emissions observatory spied on from space

While most people might be drawn to the still sunny sky, the nearby ocean, or the mountains bordering the Los Angeles Basin, environmental engineer Annmarie Eldering was drawn to the city’s smog. “This is the best place to go,” she says. “You have tons of pollution! ”

Urban areas release more than 70 percent of man-made carbon dioxide emissions that end up in the atmosphere, and LA is no exception. With more than 13 million people in its largest metropolitan area, a sophisticated network of highways and an international transportation hub, LA produces the fifth most CO2 from all the cities of the world. This makes it a great place to study the role humans play in climate change.

Eldering is the project scientist for NASA’s Orbiting Carbon Observatory-3, or OCO-3, an instrument that measures atmospheric CO2 levels from space to better understand the impact of human activity on the natural carbon cycle, the process by which plants, soil, oceans and the atmosphere exchange carbon with each other. In one article published this month, Eldering and his colleagues published a map showing the most detailed variations of CO2 on the LA basin never seen from space. This research demonstrates that space monitors can be used to collect large amounts of data on pollution hotspots, information that could help inform climate change policies.

“What’s exciting about the OCO-3 result is that this is the first time we’ve had this type of area map on a city like LA from space,” says Joshua Laughner, researcher. postdoctoral fellow at Caltech who works on a global ground-based surveillance system Total carbon column observation network. While useful for observing precisely how atmospheric carbon concentrations change over time, instruments like TCCON are expensive to operate and require partnerships with trained scientists, so their data collection is limited to specific areas. . An orbiting observatory, on the other hand, can scan parts of the planet that are difficult to study from the ground, such as volcanoes or cities with high carbon footprints but few monitoring resources.

Launched in 2019, OCO-3 is now mounted on the International Space Station, where it sees nearly every city on Earth within an average of three days, according to a NASA press release. This is an improvement over its still-active predecessor, OCO-2, which can only collect a 10-kilometer-wide data strip and is locked into a sun-synchronous orbit that passes over LA at the same time every day, which means it can only check the city’s atmospheric CO2 levels at 1:30 in the afternoon.

“With OCO-3, we have much better spatial coverage, but also temporal coverage, because it can now look at the city at different times,” says postdoctoral researcher Caltech Dien Wu, who works closely with the team in analysis of urban emissions. OCO-3 can perform multiple scans at a single location, mapping a snapshot of approximately 80 square kilometers in under two minutes.

The color of each pixel on this map created by the Eldering team represents atmospheric CO2 concentrations in a ground area approximately 1.3 miles wide. Since carbon dioxide absorbs certain wavelengths of light, scientists can use this information to infer how much is in Earth’s atmosphere. OCO-3 observed changes in the intensity of sunlight as it passed through a vertical column of air and created a reading of the amount of CO2 was at this location.

Next, the OCO-3 team compared this satellite data to the “clean air” readings already collected by a TCCON instrument on the ground at NASA’s Armstrong Flight Research Center in the desert north of Los Angeles, far from the sources of emissions. local. Using a baseline of about 410 parts per million (or 410 CO2 molecules for every million molecules of dry air), OCO-3 was able to identify differences of up to half a part per million. They saw peaks of excess CO2 to over five parts per million over the LA Basin. It may not seem like much, but it is equal to the amount that these emissions increase globally every two years.

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