Measuring Black Carbon

Black carbon sensor could fill massive monitoring gaps

February 22, 2024

Black carbon is the most dangerous air pollutant you’ve never heard of. Its two main sources, diesel exhaust and wood smoke from wildfires and household heating, produce ultrafine air particles that are up to 25 times more of a health hazard per unit compared to other types of particulate matter.


^ The AethLabs microAeth MA350. ^^ Banner Photo above: Daniel Mendoza

Despite its danger, black carbon is understudied due to a lack of monitoring equipment. Regulatory-standard sensors are wildly expensive to deploy and maintain, resulting in sparse coverage in regions infamous for poor air quality, such as the greater Salt Lake City metropolitan area in Utah.

A University of Utah-led study found that the AethLabs microAeth MA350, a portable, more affordable sensor, recorded black carbon concentrations as accurately as the Aerosol Magee Scientific AE33, the most widely used instrument for monitoring black carbon in real time. Researchers placed the portable technology next to an existing regulatory sensor at the Bountiful Utah Division of Air Quality site from Aug. 30, 2021-Aug. 8, 2022. The AethLabs technology recorded nearly identical quantities of black carbon at the daily, monthly and seasonal timescales. The authors also showed that the microAeth could distinguish between wildfire and traffic sources as well as the AE33 at longer timescales.

Because black carbon stays close to the source, equipment must be localized to yield accurate readings. The microAethsensor’s portability would allow monitoring at remote or inaccessible stationary sites, as well as for mobile use.

“Having a better idea of black carbon exposure across different areas is an environmental justice issue,” said Daniel Mendoza, research assistant professor of atmospheric sciences at the University of Utah and lead author of the study. “The Salt Lake Valley’s westside has some of the region’s worst air quality partly because it’s closest to pollution sources, but we lack the ability to measure black carbon concentrations accurately. Democratizing data with reliable and robust sensors is an important first step to safeguarding all communities from hazardous air pollution.”


Read the entire story by Lisa Potter in @TheU

Read the study published on Feb. 1, 2024, in the journal Sensors.


Read the full story by Sean Higgins at KUER 90.1.

Utah’s Warm Wet Winter

A warm, wet winter in Utah but don’t blame El Niño

February 22, 2024

For Jackie May, this winter’s rain in the Salt Lake Valley has led to a lot of second-guessing when it comes to taking the ski bus to the mountains.


She typically plans her work schedule around making time for snowboarding.

^ Michael Wasserman. ^^ Banner photo above: Fog drapes the Wasatch Mountains near Cottonwood Heights as valley rain and mountain snow have been the standard storm pattern for much of Utah this winter, Feb. 20, 2024. Credit: Sean Higgins/KUER.

“Being down here, I'm like, ‘what am I doing? Should I go back to work?’” she said while waiting for the Utah Transit Authority ski bus at the mouth of Big Cottonwood Canyon. And then when I go up in the mountains, I'm like, OK, no, [winter] is still happening. This is how I want to spend my time.”

Although this winter has not had the same record-setting snowfall as last winter, not everyone is disappointed to see no snowbanks in the valley. I don't like to shovel,” said fellow bus rider Dianne Lanoy. “I do have a good car in the snow, but I don't like to drive in the snow. So, keep [the snow] up in the mountains.”

Even with more rain than snow at the lower elevations and a slow start to the winter, snowpack levels for this time of year are above average statewide. It’s also an El Niño year. That’s when warmer, wetter weather from the Pacific Ocean moves in and usually creates more precipitation.

But don’t go blaming El Niño for this winter’s wacky weather just yet. “El Niño or La Niña really means nothing for snow and precipitation in northern Utah,” says University of Utah atmospheric sciences Ph.D. student Michael Wasserstein. “Prior literature has shown that El Niño can produce lots of precipitation in Utah, or it can produce little precipitation in Utah … I don't think we can draw any conclusions about this winter's weather based on El Niño patterns.”

Wasserstein is the lead author of a new study that dives into why the Wasatch Mountains get so much snow. As it turns out, it’s all about a diversity of storm types and weather patterns.

Read the full story by Sean Higgins at KUER 90.1.

Central Wasatch’s extreme snowfall

Where does the central Wasatch’s extreme snowfall Come From?


Utah’s famous mountains can wring a lot of snow from even low-moisture storm systems, according to new U research.

February 6, 2024


Jim Steenburgh displays a device for measuring snowfall. Credit: Brian Maffly ^^ Banner photo above: Little Cottonwood Canyon. Credit: UDOT.

Major snowstorms in Utah’s Wasatch Mountains are both a blessing and a curse. They deliver much-needed moisture that supplies water to the state’s biggest metropolitan area and fluffy light snow to support the world’s finest powder skiing.

But heavy snowfall also wreaks havoc on canyon roads and creates extreme avalanche hazards that can sometimes shut down busy winter recreation sites.  Alta at the head of Little Cottonwood Canyon, for instance, can be reached by vehicle only via a winding road that rises 3,000 feet in 8 miles, crossing about 50 avalanche paths.

University of Utah atmospheric scientists have set out to better understand extreme snowfall, defined as events in the top 5% in terms of snow accumulations, by analyzing hundreds of events over a 23-year period at Alta, the famed ski destination in the central Wasatch outside Salt Lake City. The resulting study, published this week in Monthly Weather Review, illustrates the remarkable diversity of storm characteristics producing orographic snowfall extremes in the ranges of the Intermountain West.

The orographic effect occurs when air is forced to flow up and over mountains, which cools the air and condenses its water vapor.

Some of the new findings surprised researchers. For example, they looked for an association between heavy snow and a weather factor called “integrated vapor transport,” or IVT, but found a complicated relationship.

“IVT is essentially a measure of the amount of water vapor that is being transported horizontally through the atmosphere, said lead author Michael Wasserstein, a graduate student in atmospheric sciences.  “In certain regions high IVT can produce extremely heavy precipitation. That can be the case for the Wasatch, but not always.”

In the West Coast’s Sierra Nevada and Cascade Range, by contrast, there is a stronger relationship between high-IVT storms blowing in from the Pacific and extreme precipitation and snowfall.

Spanning the years 2000 to 2022, the study, which was funded by the National Science Foundation, analyzed a total of 2,707 snow events, each covering a 12-hour period. The average amount of snow deposited during each event was 11.2 centimeters (4.4 inches), while the median amount was just 7.6 (3 inches). Alta ski patrollers did much of the data collection at the monitoring station located near the ski area’s Wildcat Lift.

The researchers homed in on “extreme” events above the 95th percentile, or 138 storms in which 30.5 centimeters (12 inches) or more snow fell. “Those would be snowfall rates of about an average of an inch an hour,” said Jim Steenburgh, the study’s senior author. The biggest 12-hour accumulation was 65 centimeters (26 inches), recorded on March 30, 2005.  They also examined “extreme” water-equivalent snowfall events above the 95th percentile, or 116 storms with at least 27.9 mm (1.11 inches) of water equivalent precipitation. The water equivalent of precipitation measures the amount of water in the snowfall and is important for water resources and avalanches.

Read the full story by Brian Maffly in @TheU

Presidential Societal Impact—Kevin Perry

Kevin Perry, Societal Impact Scholar


University of Utah President Taylor Randall has named five faculty members as 2024-25 Presidential Societal Impact Scholars for exemplary public engagement, including Atmopsheric Sciences Professor Kevin Perry.


The four include a range of faculty members whose impact varies from helping Utahns understand the danger posed by a shrinking Great Salt Lake to advocating for the rights and rehabilitation of incarcerated women and engaging college and high school students in projects that beautify public spaces with mural art.

Perry has studied the impacts of mineral dust for more than two decades, a research focus that took on major importance with the shrinking of the Great Salt Lake. Perry, riding a fat-tire bicycle, surveyed the 800-mile exposed lakebed and found dust from the lake contains high concentrations of toxic metals. To date, Perry has shared his research in three documentary films and more than 115 print, radio and TV interviews, including Popular Science, Discover Magazine, Outside Magazine, Newsweek, CNN, Le Monde and The Guardian. He has presented his findings to numerous policy-making organizations, such as the Utah Air Quality Board, Utah Clean Air Caucus, and the Utah Department of Environmental Quality. Perry has presented to many health care groups, including the Utah Public Health Association and the Central Utah Healthcare Coalition. He also serves as a member of the Great Salt Lake Strike Team and the Dust Alliance for North America. Perry also has participated in educational outreach activities, focused mostly on high school students.

Other awardees are V. Kim Martinez, professor, Department of Art & Art History; Emily Salisbury, director of the Utah Criminal Justice Center and associate professor, College of Social Work; Baodong Liu, professor, Department of Political Science and the Division of Ethnic Studies; and Amberly Johnson, director of the Utah Poison Control Center and assistant professor (clinical), College of Pharmacy.

“What is obvious in this award process is that we have many exceptional faculty who are having a broad impact,” said President Taylor Randall. “As a university, we aspire to improve the communities we serve by sharing our research and expertise in a variety of ways. Our award recipients have engaged in public activities that showcase their scholarship, influence their fields of study and contribute to the betterment of individuals and communities.”

Each scholar will receive a one-time cash award of $10,000 and support from University Marketing & Communications to promote their research, scholarship and initiatives.

Read the full press release, including details of all awardees here.

Humans of the U: Sadie Dunn

“I am currently majoring in atmospheric sciences. I just love weather. I’ve loved it since I was probably in kindergarten. So growing up, I always knew that was what I was going to study in college. When I was looking at colleges, I was kind of shocked that the University of Utah is the only school in Utah that offers an atmospheric sciences degree. So that’s how I ended up here.

The For Utah Scholarship has been an amazing opportunity for me because honestly, I would not have been able to afford college on my own. This scholarship offered me the amazing opportunity to come and study here in the department I want to be in.

I am from Chicago and I grew up with really severe summer storms in the Midwest, so I guess that’s what really fostered my love for weather. Then I moved to Utah when I was 13 and just kept loving weather. There’s a ton of snow out here and crazy windstorms which sparked my curiosity.

All throughout junior high and high school, I knew studying weather was my goal. So when I was a senior in high school, we had an internship class and I got to intern at ABC 4 news in their weather department, which was cool. That was definitely the moment when I was like, ‘This is real. I’m working towards this and this is the goal.’ So it’s really exciting to take this love I’ve had since I was little and turn it into a career.

While interning at a broadcast station was fun, it’s not something that interests me as a career. But my atmospheric sciences degree can take me a bunch of different places. It offers research opportunities with organizations like the National Weather Service and the National Oceanic and Atmospheric Administration (NOAA). You can also work with private organizations. There are serious meteorologists in every field, which I think is one of the coolest parts about this job.

I’m still kind of feeling out what I want to do. It’s a STEM major and it’s very math- and physics- and chemistry-heavy. I consider myself to be smart, but I am not a natural in those courses. So I don’t think research is something I will do. I am really passionate about climate change, so I’m looking more into the field of sustainability.

Since I grew up with a love of severe weather, I would also love to be able to get a career that helps with the effects of those disasters, because it’s hard with hurricanes and tornadoes. You can’t stop them. They are going to hit and destroy everything. So I would love to find ways to lessen the effects of those or find better ways to prepare the communities.”

—Sadie Dunn, recipient of the For Utah Scholarship

This story originally appeared in @TheU.

Holiday Greetings from Dean Trapa



Dear Friends and Colleagues,

As the fall semester draws to a close, I want to take a moment to wish you and your loved ones a happy and restful holiday season.  This time of year invites reflection on all that we have to be thankful for.

Here at the College of Science, I am grateful to our exceptional students, faculty and staff, whose passion for discovery and commitment to excellence make the College a vibrant place of learning and innovation.   I also want to thank our alumni and donors for their steadfast support, making possible transformative educational opportunities and enabling us to pioneer new research directions.  I am deeply grateful for all of you and for your involvement and investment in our mission.

Warmest thoughts and best wishes for a joyful holiday season and a wonderful New Year!


Dean Peter Trapa
College of Science
University of Utah

Snowflakes Falling

The science behind snowflakes

In a study that could enhance weather forecasting, Utah researchers discover that how snowflakes move is astonishingly predictable.


Tim Garrett

Tim Garrett has devoted his scientific career to characterizing snowflakes, the protean particles of ice that form in clouds and dramatically change as they fall to Earth.

Now the University of Utah atmospheric scientist is unlocking the mystery of how snowflakes move in response to air turbulence that accompanies snowfall using novel instrumentation developed on campus. And after analyzing more than half a million snowflakes, what his team has discovered has left him astonished.

Rather than something incomprehensibly complicated, predicting how snowflakes move proved to be surprisingly simple, they found.

“How snowflakes fall has attracted a lot of interest for many decades because it is a critical parameter for predicting weather and climate change,” Garrett said. “This is related to the speed of the water cycle. How fast moisture falls out of the sky determines the lifetime of storms.”

“Letters sent from Heaven”

The famed Japanese physicist Ukichiro Nakaya termed snow crystals “letters sent from heaven” because their delicate structures carry information about temperature and humidity fluctuations in the clouds where crystal basal and prism facets competed for water vapor deposition.

While every snowflake is believed to be unique, how these frosty particles fall through the air—as they accelerate, drift and swirl—follows patterns, according to new research by Garrett and colleagues in the College of Engineering. Snowflake movement has important implications for weather forecasting and climate change, even in the tropics.

“Most precipitation starts as snow. How the question of how fast it falls affects predictions of where on the ground precipitation lands, and how long clouds last to reflect radiation to outer space,” Garrett said. “It can even affect forecasts of a hurricane trajectory.”

Read the full article by Brian Maffly in @TheU.
Read additional coverage of this article in  and Science News.

Cold Fog & Complex Terrain

Cold fog & Complex Terrain


You might not initially think of fog as a form of severe weather, but when fog sets in and visibility plummets, transportation becomes dangerous.

Zhaoxia Pu

Fog is the second-most-likely cause of aircraft accidents after strong winds, but despite the high impact of fog events and a long history of research, fog prediction remains a long-standing challenge for weather prediction because of complex interactions among the land surface, water, and atmosphere. There’s still a lot of fundamental things about fog that we don’t know.

Zhaoxia Pu, University of Utah professor of atmospheric sciences and Eric Pardyjak, professor of mechanical engineering, hope to change that through a field campaign and scientific research using Utah’s Heber Valley as the laboratory.

For about six weeks, from 7 January to 24 February 2022, Pu, Pardyjak and their colleagues, including scientists from the National Center for Atmospheric Research (NCAR) and the Environment and Climate Change Canada as well as graduate students and undergraduate students from atmospheric sciences and mechanical engineering at the University of Utah, watched a network of sensors on the ground in the Heber Valley along with comprehensive sets of instruments from the NCAR's Erath Observing Laboratory and satellite observations. The valley is bounded by mountains, relatively flat in the basin and features two lakes — Jordanelle and Deer Creek reservoirs. Its conditions, Pu says, are representative of mountain valleys around the world.

On winter nights, cold air pools on the valley floor and creates favorable conditions for several forms of fog, including cold-air pool fog, ephemeral mountain valley cold fog and radiative ice fog. By observing how these different kinds of fog form and dissipate, the researchers are continuing to learn about the meteorological conditions and physical processes governing the formation of fog and improve fog prediction.

The study is funded by a $1.17 million grant from the National Science Foundation.

Now, in a recent paper in the Bulletin of the American Meteorological Society, Pu and her colleagues have published findings via The Cold Fog Amongst Complex Terrain (CFACT) project, conceived to investigate the life cycle of cold fog in mountain valleys.

The overarching goals of the CFACT project, according to the paper’s abstract, are to 1) investigate the life cycle of cold-fog events over complex terrain with the latest observation technology, 2) improve microphysical parameterizations and visibility algorithms used in numerical weather prediction (NWP) models, and 3) develop data assimilation and analysis methods for current and next-generation (e.g., sub kilometer scale) NWP models.

Field observations, NWP forecasts, and large-eddy simulations provided unprecedented data sources to help understand the mechanisms associated with cold-fog weather and to identify and mitigate numerical model deficiencies in simulating winter weather over mountainous terrain. The paper summarizes the CFACT field campaign, its observations, and challenges during the field campaign, including real-time fog prediction issues and future analysis.

Comprehensive measurements

A network of ground-based and aerial in situ instruments and remote sensing platforms were used to obtain comprehensive measurements of thermodynamic profiles, cloud microphysics, aerosol properties and environmental dynamics. Over its seven-week course, the CFACT field campaign collected a diverse and extensive dataset, including high-frequency radiosonde profiles, tethered balloon profiles, remotely sensed thermodynamic and wind profiles, numerous surface meteorological observations, and microphysical and aerosol measurements. Nine intensive observation periods (IOPs) explored various mountainous weather and cold fog conditions.

Despite the drought in the western United States in 2022, which limited the occurrence of persistent deep fog events associated with persistent cold-air pools that regularly form in higher-elevation Intermountain West basins, the campaign observed highly spatially heterogeneous ephemeral fog and ice fog events. Since ephemeral fog and ice fog are extremely difficult to detect, model, and forecast, CFACT provided unprecedented datasets to understand both types of fog and validate the NWP model.

Meanwhile, the variety of non-fog IOPs provided valuable observations for understanding near-surface inversion, ice crystal formation, moisture advection and transportation, and stable boundary layers over complex terrain, all of which are essential factors related to fog formation. Comprehensive studies are ongoing for an improved understanding of cold fog over complex terrain.

Critical high resolution observations

The CFACT campaign observations, complemented by model simulations, have been instrumental in studying the lifecycle of fog and the behavior of the stable boundary layer. More importantly, since Heber Valley is a small-scale valley, the observations from the two CFACT supersites, eight low-cost stations and nine satellite sites provide critical high-resolution observations to validate and improve current and next-generation (i.e., sub-kilometer scale) NWP models.

Moreover, the available CFACT high-resolution meteorological observations, along with the soil and snow observations during CFACT, are helpful for developing fine-scale atmospheric data assimilation and the coupled land–atmosphere data assimilation (e.g., Lin and Pu 2019, 2020; Zhang and Pu 2019) for improved near-surface weather prediction, including cold-fog forecasting.

Various comprehensive studies are presently underway for numerical model validation, improvement and data assimilation to improve cold-fog prediction.

First author of the paper, Zhaoxia Pu is a member of the NOAA Science Advisory Board. She is an elected fellow of the American Meteorological Society and Royal Meteorological Society.

This story is adapted from an earlier announcement on this project by Paul Gabrielsen in @TheU.

UPDATE (Dec.19, 2023): With the persistent "inversion" now occurring in the Salt Lake Valley and beyond,
additional coverage from FOX 13 of Dr. Pu's research has been broadcasted / posted.
Listen to the story here.

UPDATE (Feb. 13, 2024): The EOS newsletter of American Geophysical Union  (AGU)
featured the CFACT project here.

Do the Right Thing: Kevin Perry on the GSL

Do the Right Thing

Dr. Kevin Perry, an atmospheric scientist at the University of Utah, is one of the scientists working to save the Great Salt Lake from drying up.

The lake needs all the help it can get—informing citizens and policymakers on the science of the lake is critical to keep it going for years to come. Lately, Perry says more of his time is spent communicating about his research than actually doing it.

In 2021, Perry presented the findings of a two-year research project to determine the contents of the dust coming off of the dried Great Salt Lake surface. He found that not only was the dust a source of pollution, but it also released toxic chemicals like arsenic and other heavy metals into the air. The potentially harmful air pollutant would only worsen if the lake wasn’t restored—and he’s been trying to get Utahns to listen ever since.

While Perry was out buying groceries, a cashier struck up a conversation with him about the Great Salt Lake. The cashier said he had created a website to warn community members about dust pollutants coming off the Great Salt Lake and started to explain the risk of the exposed lakebed to Perry.

“I laughed and I said, ‘You don’t know who I am, but you know the toxic dust that you’re talking about? That’s my scientific research,’” Perry says. “That kind of blew me away…when [I saw] somebody who has no scientific background was inspired enough to spend their time and effort trying to save the Great Salt Lake.”

Read the full article in Scientist Stories by Science Friday's Emma Lee Gometz.

‘Roving sentinels’ discover new air pollution sources

‘Roving sentinels’


In 2019, University of Utah atmospheric scientists, the Environmental Defense Fund and other partners added a new tool to their quiver of air quality monitors—two Google Street View cars, Salt Lake Valley’s roving sentinels that would detect hyper-local air pollution hotspots.

Jon Lin. Banner Photo: A Google Street Car loaded with air quality instrumentation. Credit: Logan Mitchell

In the ensuing months John Lin, professor of atmospheric sciences at the U, developed a new modeling approach that used modeled wind patterns and statistical analysis to trace pollution back to its source location to a scale previously missed by coarser scale monitoring projects that have traditionally characterized air quality averaged over an entire urban airshed.

In a U- and Environmental Defense Fund (EDF)-led study that was published in the October 2023 issue of the journal Atmospheric Environment, the results are in.

“With mobile vehicles, you can literally send them anywhere that they could drive to map out pollution, including sources that are off the road that previous monitoring missed,” said Lin, who also serves as associate director of the Wilkes Center for Climate Science & Policy. “I think the roving sentinel idea would be quite doable for a lot of cities.”

The researchers loaded the vehicles with air quality instrumentation and directed drivers to trawl through neighborhoods street by street, taking one air sample per second to create a massive dataset of air pollutant concentrations in the Salt Lake Valley from May 2019 to March 2020. The observations yielded the highest-resolution map yet of pollution hotspots at fine scales—the data captured variability within 200 meters or about two football fields.

“The big takeaway is that there is a lot of spatial variability of air pollution from one end of a block to another. There can be big differences in what people are breathing, and that scale is not captured by the typical regulatory monitors and the policy that the U.S. EPA uses to control air pollution,” said Tammy Thompson, senior air quality scientist for EDF and co-author of the study.

Read the full story by Lisa Potter in @TheU.