About

Tracey Holloway is the Jeff Rudd and Jeanne Bissell Professor of Energy Analysis and Policy at the University of Wisconsin–Madison. She is jointly appointed in the Nelson Institute for Environmental Studies and the Department of Atmospheric and Ocean Sciences. Based in the Nelson Institute Center for Sustainability and the Global Environment, her group works at the intersection of air quality, energy, climate, and public health. Dr. Holloway has been recognized as a member of the National Academy of Medicine and has received the Ascent Award from the American Geophysical Union Atmospheric Sciences Section, along with multiple awards for science outreach, diversity, and mentoring. She serves as the two-time Leader of the NASA Health and Air Quality Applied Sciences Team, which connects NASA data with stakeholder interests in air quality management and public health, and she chairs the Energy Analysis and Policy graduate certificate at UW–Madison. Her academic background includes an ScB with honors in applied math from Brown University and a PhD in atmospheric and oceanic sciences with a graduate certificate in science, technology, and environmental policy from Princeton University. Following her doctoral studies, she completed a postdoctoral fellowship with the Columbia University Earth Institute, working with the Mailman School of Public Health.

Research topics

• Meteorology
• Environmental science
• Engineering
• Geography
• Chemistry
• Natural resource economics
• Geology
• Atmospheric sciences
• Environmental economics
• Economics
• Environmental planning
• Business
• Physics
• Remote sensing
• Environmental health
• Medicine

Selected publications

• Assessing Near‐Source Health and Equity Impacts of Liquefied Natural Gas Terminals

  GeoHealth · 2026-04-01

  articleOpen access

  Abstract Growing global demand for natural gas has driven the expansion of liquefied natural gas (LNG) export terminals, which emit pollutants that can pose health risks to nearby communities. This study presents a novel modeling framework using the AMS/EPA Regulatory Model (AERMOD) to assess near‐source nitrogen dioxide (NO 2 ) exposure, health impacts, and equity implications at the block‐group level. We apply this methodology to four LNG export terminals in the United States, simulating NO 2 concentrations within a 50 km radius. Results show that LNG terminals substantially contribute to near‐source air pollution, with simulated 1‐hr maximum NO 2 concentrations reaching up to 16% of the EPA's National Ambient Air Quality Standard (100 ppb). Site‐specific maximum concentrations were 15.7 ppb (Site A), 1.6 ppb (B), 10.7 ppb (C), and 0.3 ppb (D). Comparing NO 2 concentrations with demographic patterns, Sites A and D showed higher concentrations, higher proportions of People of Color and low‐income populations, and greater health burdens in communities closer to the LNG facilities, indicating potential disproportionate impacts. The other sites showed weak or no spatial inequity patterns. Estimated annual NO 2 ‐attributable all‐cause mortality rates per 100,000 people were 8.2 (A), 0.6 (B), 2.2 (C), and 0.1 (D); annual NO 2 ‐attributable pediatric asthma rates per 100,000 children were 75.5 (A), 6.2 (B), 21.8 (C), and 1.1 (D). This study demonstrates how regulatory dispersion models like AERMOD can be adapted to evaluate near‐source health and equity impacts of industrial emissions and offers a transferable methodology for similar analyses across other high‐emitting facilities.

  PublisherDOI

• Satellite Detection of NO ₂ Distributions and Comparison with Ground-Based Concentrations

  2025-02-13 · 1 citations

  preprintOpen access

  Abstract. In this study we assess the capability of current-generation satellites to capture the variability of near-surface nitrogen dioxide (NO2) monitoring data, with the goal of supporting health and regulatory applications. We consider NO2 vertical column densities (VCD) over the United States from two satellite instruments, the Tropospheric Monitoring Instrument (TROPOMI), and Tropospheric Emissions: Monitoring of Pollution (TEMPO), and compare with ground-based concentrations as measured by the EPA’s Air Quality System (AQS) monitors. While TROPOMI provides a longer-term record of assessment (2019–2023), TEMPO informs diurnal patterns relevant to evaluating peak NO2. We analyze frequency distributions and quantify their similarity using the Jensen-Shannon Divergence (JSD), where smaller values indicate better agreement. Satellite and ground monitor NO2 distributions are most similar away from major roads, as indicated by the JSD of 0.008 calculated for TROPOMI and ground monitors at non-roadways, compared with a JSD near interstates of 0.158 and a JSD near highways of 0.095. Seasonal analysis shows the most similarity in distributions in winter, with a JSD of 0.010, and the most difference in summer, with a JSD of 0.035. Across seasons and monitor locations, TEMPO consistently has a lower or similar JSD as TROPOMI, with TEMPO JSDs ranging from 0.005 to 0.151 and TROPOMI JSDs ranging from 0.012 to 0.265. TEMPO’s agreement with monitors in both December 2023 and July 2024 is found to be best around midday, with non-road monitors’ JSD in July as low as 0.008 at 16 UTC (~11 am LT).

  PublisherDOI

• Supplementary material to "Satellite Detection of NO ₂ Distributions and Comparison with Ground-Based Concentrations"

  2025-02-13

  preprintOpen access
  PublisherDOI

• The hours matter: comparing indicators of US residential cooling from hourly versus daily climate variables

  Environmental Research Letters · 2025-03-06 · 2 citations

  articleOpen access

  Abstract Cooling energy demand in buildings is rapidly increasing as climate warms. Current methods of estimating and predicting residential cooling demand are primarily based on daily temperature, which neglects intraday temperature variations. To determine whether large-scale cooling demand is substantially affected by intraday temperature variations, we conduct a thorough comparison between variable degree days (VDDs) derived from daily temperature data with variable degree hours (VDHs) derived from hourly temperature data during the summer seasons in the United States. The results imply that incorporating intraday variations in temperature will have substantial impacts on cooling estimation and prediction. A comparison of the historical (1990–2014) VDD and VDH calculated from ERA5 temperature data reveals that US summer cooling demand estimated from hourly temperature is 29%–45% higher than those estimated from daily temperature, with differences exceeding 60% when hourly solar radiation is considered. This occurs because the hourly calculations captures the ‘hot hours’ of the mild days. Future scenario analysis, using the NASA Earth Exchange Global Daily Downscaled Projections, indicates that under the medium greenhouse gas emissions pathway (SSP2-45), US summer VDH and VDD are expected to increase by approximately 45% and 100% by the late century (2081–2100). This suggests that, daily-based predictions generally project cooling demand growth at twice the rate of hourly-based predictions, as the daily method accounts for increases in both high and low temperatures regardless of whether they exceed the baseline, while the hourly method, with its finer temporal resolution, includes only temperatures that surpass the baseline. Such effects are seen across most areas of the US. Our analysis underscores the significance of incorporating temperature data at higher temporal resolution in estimating and predicting cooling demand, which is essential for effectively implementing various measures to achieve energy conservation and climate goals.

  PublisherOA PDFDOI

• Insights Into Summertime Surface Ozone Formation From Diurnal Variations in Formaldehyde and Nitrogen Dioxide Along a Transect Through New York City

  Journal of Geophysical Research Atmospheres · 2025-05-12 · 6 citations

  articleOpen accessSenior author

  Abstract Estimating tropospheric ozone (O 3 ) production from observations is challenging but possible given the close coupling of O 3 with formaldehyde (HCHO) and nitrogen dioxide (NO 2 ), two remotely sensed air pollutants. The previous reliance on once‐daily satellite overpasses highlights the need to study diurnal changes and surface‐column relationships. Using surface observations, Pandora spectrometer retrievals, and a high‐resolution (1.33 km) air quality model (WRF‐CMAQ), we characterize diurnal patterns of HCHO and NO 2 at seven locations along an upwind‐downwind pathway through New York City during June–August 2018. Diurnal patterns of limited surface HCHO measurements suggest biogenic emission influence, while a bimodal surface NO 2 pattern indicates the impact of local anthropogenic nitrogen oxides emissions. Details of these patterns vary by site: an afternoon NO 2 spike at New Haven (CT) indicates traffic emissions, while a delayed daily HCHO peak at Westport (CT) relative to other sites likely reflects sea breeze dynamics. Peak column concentrations generally lag surface peaks by about four hours, occurring at 9–10 a.m. for morning NO 2 (from Pandora and WRF‐CMAQ) and around 4 p.m. for midday HCHO (from WRF‐CMAQ). TROPOMI overpass time at 1:30 p.m. misses peak column HCHO and NO 2 concentrations. A box model (F0AM) constrained with site‐level observations and WRF‐CMAQ fields indicates 1–9 ppb hr −1 higher noontime local O 3 production rates on three sets of paired high‐ versus mid‐to‐low‐O 3 days. F0AM sensitivity analyses on these six days suggest a predominantly transitional O 3 formation regime at urban and downwind sites, differing at some sites from the NO x ‐saturated regime diagnosed for summertime average conditions via the weekday‐weekend effect.

  PublisherOA PDFDOI

• Emissions Reductions to Meet a Tighter Ozone Standard in the U.S. through Control Technologies versus Clean Energy Transition Scenarios

  Environmental Science & Technology · 2025-12-15

  articleOpen access

  Past studies have found that carbon reduction strategies generally reduce emissions of nitrogen oxides (NOX) and/or volatile organic compounds (VOCs). The reverse is not true, however, as evidenced by over 50 years of air quality improvements in the U.S. with only modest reductions of carbon dioxide (CO2) emissions. This analysis compares energy and emissions pathways to achieve NOX and VOCs targets calculated by the U.S. Environmental Protection Agency (EPA) to meet a hypothetical 65 ppb revision to the National Ambient Air Quality Standard (NAAQS) for ozone. To meet these targets, we model sector-specific reductions over a 15-year horizon with the Multipollutant Emissions Calculator for Air Quality and Climate (MECAQC), considering both conventional emission controls, e.g. technologies, as well as energy system changes, e.g., fuel-switching. Switching away from conventional fuels can achieve the majority of required NOX and VOCs emission reductions, considering maximum decarbonization up to 45% for heavy-duty vehicles, up to 65% for light-duty vehicles, up to 36% for building electrification, and up to 100% for electricity generation. The maximum decarbonization assumptions alone could meet NOX and VOCs targets in the Midwest region and VOCs targets in the Northeast region, reducing NOX emissions in affected areas by 44%, VOCs by 16%, and CO2 by 56%. These carbon-reduction strategies may be supplemented by conventional emission controls to achieve additional VOCs reductions to meet the most targets: reducing NOX emissions in affected areas by 33%, VOCs by 17%, and CO2 by 35%. Conventional controls alone could meet all regional targets except the California NOX target, which cannot be met by any approach evaluated here, reducing NOx emissions in affected areas by 33% and VOCs by 17%, but increasing emissions of CO2 by 1.4%.

  PublisherDOI

• Using Satellites to Track Indicators of Global Air Pollution and Climate Change Impacts: Lessons Learned From a NASA‐Supported Science‐Stakeholder Collaborative

  UNC Libraries · 2025-06-26

  articleOpen access

  The 2018 NASA Health and Air Quality Applied Science Team (HAQAST) "Indicators" Tiger Team collaboration between NASA-supported scientists and civil society stakeholders aimed to develop satellite-derived global air pollution and climate indicators. This Commentary shares our experience and lessons learned. Together, the team developed methods to track wildfires, dust storms, pollen counts, urban green space, nitrogen dioxide concentrations and asthma burdens, tropospheric ozone concentrations, and urban particulate matter mortality. Participatory knowledge production can lead to more actionable information but requires time, flexibility, and continuous engagement. Ground measurements are still needed for ground truthing, and sustained collaboration over time remains a challenge.

  PublisherDOI

• Satellite detection of NO ₂ distributions using TROPOMI and TEMPO and comparison with ground-based concentration measurements

  Atmospheric chemistry and physics · 2025-07-31 · 9 citations

  articleOpen access

  Abstract. In this study we assess the capability of current-generation satellites to capture the variability of near-surface nitrogen dioxide (NO2) monitoring data, with the goal of supporting health and regulatory applications. We consider NO2 vertical column densities (VCDs) over the United States from two satellite instruments, the Tropospheric Monitoring Instrument (TROPOMI) and Tropospheric Emissions: Monitoring of Pollution (TEMPO), and compare them with ground-based concentrations as measured by the EPA's Air Quality System (AQS) monitors. While TROPOMI provides a longer-term record of assessment (2019–2023), TEMPO informs diurnal patterns relevant to evaluating peak NO2. We analyze frequency distributions and quantify their similarity using the Jensen–Shannon divergence (JSD), where smaller values indicate better agreement. Satellite and ground monitor NO2 distributions are most similar at non-roadway monitors (JSD =0.008) and are most different at interstate (JSD = 0.158) and highway (JSD =0.095) monitors. Seasonal analysis shows the greatest similarity in distributions in winter (JSD =0.010) and the greatest difference in summer (JSD =0.035). Across seasons and monitor locations, the calculated 13:30 LT TEMPO consistently exhibits JSDs that are better than or comparable to TROPOMI (TEMPO: 0.005–0.151; TROPOMI: 0.012–0.265). TEMPO's agreement with monitors, in both December 2023 and July 2024, is found to be best around midday, with non-road monitors in July having the best alignment (JSD =0.008) at 16:00 UTC (≈11:00 LT). These findings highlight the ability of TROPOMI and TEMPO to complement existing ground-based monitors and demonstrate their potential for monitor siting, regulatory, and public health applications.

  PublisherOA PDFDOI

• Satellite data to support air quality assessment and management

  Journal of the Air & Waste Management Association · 2025-05-28 · 9 citations

  review1st authorCorresponding

  , include use in health risk assessment, constraining emissions inventories, and supporting tracking short- and long-term trends with regulatory relevance. Solutions co-developed between researchers and practitioners show promise for continued improvements in the use and value of satellite data for air quality applications.

  PublisherDOI

• Discussion of “Satellite data to support air quality assessment and management”

  Journal of the Air & Waste Management Association · 2025-10-01

  letter

  Discussion of “Satellite data to support air quality assessment and management”

  PublisherDOI

Frequent coauthors

• Jonathan A. Patz

  58 shared

• Scott N. Spak

  University of Iowa

  32 shared

• Jonathan A. Foley

  29 shared

• Monica Harkey

  29 shared

• Holly Gibbs

  Leiden University

  28 shared

• Ruth DeFries

  Columbia University

  27 shared

• Christopher J. Kucharik

  University of Wisconsin–Madison

  27 shared

• Chad Monfreda

  Princeton University

  27 shared

Labs

• The Holloway GroupPI

Education

• Ph.D., Atmospheric and Oceanic Sciences

  Princeton University

  2001

• Sc.B., Applied Mathematics

  Brown University

  1995

Awards & honors

• Member of the National Academy of Medicine
• Ascent Award from the American Geophysical Union Atmospheric…
• Multiple awards for science outreach, diversity, and mentori…
• Two-time Leader of the NASA Health and Air Quality Applied S…