One-on-One with Tier One: Dr. Yunsoo Choi


Dr. Yunsoo Choi is an assistant professor at UH working on the SPOCK detection system.

Dr. Yunsoo Choi is an assistant professor at UH working on the SPOCK detection system. Photo courtesy of UH Media Relations.

As climate change and global warming become increasingly severe problems around the world, researchers are looking into ways to monitor and forecast the pollution that contributes to this borderless issue. At the University of Houston, Dr. Yunsoo Choi (YC), assistant professor of Atmospheric Chemistry, Atmospheric Modeling and Remote Sensing, has developed a short-term pollution model for southeast Texas and the continental U.S. named the System of air POllution forecasting with Captain Kirk (SPOCK). He agreed to talk to UH’s Division of Research (DOR) about his model and his upcoming projects.

That’s an interesting name.

Yes, we all thought it would be a neat name, because many of us in the lab are Star Trek fans.

Tell us about your model.

In our lab, our main goal is to monitor and predict air quality. Every day, we perform simulations and produce forecasts for up to two days in advance, and the up-to-date modeling is available publically on our website. The predictions are important because if the concentrations of ozone are particularly high, these have the greatest impact on children and seniors. We also forecast aerosols, or PM2.5. The pollutants we forecast have the greatest impact on children, seniors, and those with respiratory diseases like asthma. This kind of air-quality forecasting system is critical to those populations, and they should keep up with air quality to monitor their risk. This sort of information can be used, let’s say, at an elementary school. Perhaps recess is scheduled at 3 p.m. today, but the teacher then sees that the ozone is too high at that time from the forecasting system through the web, but is less severe at maybe 1 or 2 p.m. Recess for the kids could be adjusted to protect them.

Not only do we forecast ozone and aerosols, we also track meteorological data and carbon monoxide (CO), which is a toxic gas. On top of that, we are the only air-quality forecasting lab to operate an air quality forecasting system in Texas. As far as I know, the University of Texas at Austin, Texas A&M and Rice University do not have the operating air quality forecasting system that we have here in my lab.

As we all know, Houston can get hot. How does heat contribute to higher ozone readings?

Certain gases and pollutants have specific times of the day that they’re more abundant. Nighttime ozone is very low, because the cooler temperature allows for a higher concentration of nitrogen oxides (NOx) to form a layer on the shallow air surface. The high NOx in the urban region push down ozone closer to zero, and the lack of sunlight and the presence of cooler temperature impede a photochemical reaction that causes ozone from occurring. However, as the sun rises and the temperature rises, the photochemical reaction between NOx, CO and volatile organic compounds (VOCs) occurs, and ozone is produced in larger quantities.

Higher temperatures in Houston not only trigger the trees to produce more volatile organic carbon, such as isoprene, which is an important ozone ingredient, but higher temperatures also make all the photochemical reactions of anthropogenic chemicals, such as those from industry or vehicles, to produce ozone faster.

How does your model improve on other methods for measuring ozone, and how do you gauge the accuracy of your model?

Our model can help us predict altitude. The remote sensing data are very good at helping us see where the pollutants are from space, but scientists have had the problem of determining the altitude of such pollutants. Sometimes, the chemicals might be located right on the surface of the Earth. Other times they could be a mile up in the free troposphere. It’s hard to tell. My lab uses many different kinds of remote sensing data, which we then use to compare how accurate our predictions were.

Dr. Choi's research team works on SPOCK with him. From left to right: Joey Rodriguez, Dr. Beta Czader, Lijun Diao, Choi and Shuai Pan.

Dr. Choi’s research team works on SPOCK with him. From left to right: Joey Rodriguez, Dr. Beta Czader, Lijun Diao, Choi and Shuai Pan. Photo courtesy of Choi.

What are your next steps for this project?

In the future, we are both going to improve our forecasting system and branch out into different modeling systems. It is quite difficult to make a good air-quality-forecasting model. There is a lot of uncertainty that goes into it. With new funding from The Sandia National Laboratories, the Korea Institute of Atmospheric Research Systems and the Texas Air Research Center, our next direction from here is taking into account air quality change and climate change. How will the changing Earth affect the air quality? This is going to be very interesting and challenging for us because there are different problems and considerations that are associated with long-term forecasting than there are with short-term forecasting.

Using our model, we can simulate what would happen if an industry were to make certain specific energy source changes, such as if they used a different fuel source. We can simulate this by changing the emission sources in our model.

To check out the pollution in your area, visit Choi’s research website.

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