State of the Planet

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Xiaomeng Jin Uses Satellite Imagery to Track Ozone Formation

Xiaomeng Jin
Lamont Ph.D. student Xiaomeng Jin defends her thesis next month. Photo courtesy Xiaomeng Jin

Next month, when Lamont Ph.D. student Xiaomeng Jin defends her thesis, she will have a significant body of work to reference. During her five years at Lamont-Doherty Earth Observatory, working as part of atmospheric chemist Arlene Fiore’s laboratory, Jin has published four first-authored papers and co-authored four additional papers. Along the way, she has found new ways to track and interpret ozone formation.

Atmospheric chemistry was not on Jin’s radar at the beginning of her academic career.

She focused on engineering in her undergraduate program, where her senior thesis led to two journal articles in Remote Sensing and International Journal of Climatology. Then it was off to the University of Wisconsin-Madison and a master’s research program with professor Tracey Holloway, who leads an air quality research program there. It was her work with Holloway’s group that inspired Jin to study atmospheric chemistry and motivated her to pursue a career in earth science. Jin says the rigor of this program prepared her well for her research life at Lamont.

During her time at the observatory, Jin has drawn high honors. She received the American Geophysical Union Outstanding Student Presentation Award in Fall 2016 and Fall 2019. She has received the NASA Earth and Space Science Fellowship, and made significant strides in the understanding of the chemistry driving ozone formation, which in turn has yielded important information for air quality control efforts. Most recently, her work included a unique approach to investigating satellite images and linking that data to ground-level ozone.

Last month, Environmental Sciences & Technology published Jin’s fourth paper, which builds on her earlier work at Lamont. This latest study was motivated by pervasive summertime ozone pollution across the U.S., and more broadly in densely populated world regions where ozone levels exceed health standards. Ground-level ozone is created by chemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOC) in the presence of sunlight. Environmental health researchers have found that exposure to ozone in these summertime concentrations can trigger coughing, throat irritation, and make existing ailments such as bronchitis, emphysema, and asthma worse. Ground-level ozone may also reduce lung function and inflame the linings of the lungs.

While ozone pollution near Earth’s surface is one of the main ingredients of summertime smog, it is not directly measurable from space, because the abundance of ozone higher in the atmosphere masks the surface. In earlier research, Jin used satellite measurements of the two different precursor gases that contribute to ozone formation (NOx and VOCs), and by using them as tracers, was able to track changes in this chemistry over the past decade. In this way, she was able to look at the impact of emission controls on surface ozone. In the latest study, Jin has extended the record of air analysis to two decades (1996-2016) by using multiple satellites, and—for the first time—connected this data directly to ozone observations on the ground. By doing so, she has found a way to confirm that the satellite data is telling us important information about ozone in surface air where humans breathe.

Ozone production over Eastern USA, Europe and East Asia, derived from satellite observations in Jin’s 2017 study. The satellite data shows the effectiveness of air pollution controls that were enacted between 2005 and 2015. Image: NASA’s Earth Observatory /Josh Stevens

“Air pollution is the fifth leading risk factor for mortality worldwide. As an atmospheric chemist, a basic question I address is: ‘Where do the air pollutants come from and how do they impact us?’ A major limitation to advancing our understanding of the cause and impacts of air pollution is the lack of observations with the spatial and temporal resolution needed to observe variability in emission, chemistry, and population exposure,” said Jin. That is why her use of satellite instruments, with their long-term, global, and continuous observations of the Earth’s atmosphere, could prove to be extremely valuable for air quality monitoring.

“The exciting result holds promise for wider application,” said Fiore, who is Jin’s academic advisor.

The study caps a period of productive research. Fiore says Jin’s approach to inquiry has served her well at Lamont and will continue to do so as the atmospheric chemist moves further into her scientific career.

Fiore said that in addition having expertise with various types of air pollutants, “Xiaomeng isn’t afraid to ask tough questions that can reveal both limitations in prior assumptions and new insights into atmospheric processes. She has a real knack for combining different kinds of datasets in new ways.”

Jin’s next research assignment involves postdoctoral work at the University of California Berkeley. She was awarded the NOAA Climate and Global Change Postdoctoral Fellowship, which will support her study of the impacts of wildfires on atmospheric composition.

For Jin, the conclusion of her studies at Lamont has a bittersweet aspect. The coronavirus pandemic is making it more difficult to say goodbye.

“It will be a big milestone to be awarded a Ph.D. from Columbia. My parents in China are also proud of me being the first one to receive a Ph.D. in my extended family. Unfortunately, I won’t be able to celebrate my graduation with my advisor and friends in person, but I have had a lot of joy and happiness in the past five years at Lamont.”

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