About

The faculty, staff and students in the Department of Atmospheric and Climate Science at the University of Washington are engaged in the study of a broad range of atmospheric phenomena and processes, using methods ranging from mathematical analysis to field experimentation. Research projects range in size from small studies involving individual scientists to large national and international programs involving teams of scientists. Research groups in the department are concerned with Atmospheric Chemistry, Atmospheric Dynamics, Boundary Layer Processes, Cloud and Aerosol Research, Glaciology and Planetary Atmospheres, Cloud Dynamics, Precipitation Processes, Storms, Weather Analysis and Forecasting, Climate, Global change, Airflow over mountains, and other topics. Some groups maintain special research facilities for the use of their students. In some of these activities, there is close cooperation with the University of Alaska Fairbanks, Oregon State University and the National Oceanic and Atmospheric Administration (NOAA) Regional Center through the Cooperative Institute for Climate, Ocean and Ecosystem Studies. Faculty members often have interests in more than one area, and research projects frequently involve questions of broad scope which do not fall neatly into a single category. This is particularly true of research projects directed toward understanding the chemical and physical modification of the environment by human activities.

Research topics

• Chemistry
• Environmental chemistry
• Meteorology
• Organic chemistry
• Photochemistry

Selected publications

• Night-time NO emissions strongly suppress chlorine and nitrate radical formation during the winter in Delhi

  2023 · 5 citations

  • Chemistry
  • Environmental chemistry
  • Meteorology

  Abstract. Atmospheric pollution in urban regions is highly influenced by oxidants due to their important role in the formation of secondary organic aerosol (SOA) and smog. These include the nitrate radical (NO3), which is typically considered a night-time oxidant, and the chlorine radical (Cl), an extremely potent oxidant that can be released in the morning in chloride-rich environments as a result of nocturnal build-up of nitryl chloride (ClNO2). Chloride makes up a higher percentage of particulate matter in Delhi than has been observed anywhere else in the world, which results in Cl having an unusually strong influence in this city. Here, we present observations and model results revealing that atmospheric chemistry in Delhi exhibits an unusual diel cycle, controlled by high concentrations of NO during the night. As a result of this, the formation of both NO3 and dinitrogen pentoxide (N2O5), a precursor of ClNO2 and thus Cl, are suppressed at night and increase to unusually high levels during the day. Our results indicate that a substantial reduction in night-time NO has the potential to increase both nocturnal oxidation via NO3 and the production of Cl during the day.

  DOI

• Nighttime NO emissions strongly suppress chlorine and nitrate radical formation during the winter in Delhi

  Atmospheric chemistry and physics · 2023 · 15 citations

  • Chemistry
  • Environmental chemistry
  • Photochemistry

  Abstract. Atmospheric pollution in urban regions is highly influenced by oxidants due to their important role in the formation of secondary organic aerosol (SOA) and smog. These include the nitrate radical (NO3), which is typically considered a nighttime oxidant, and the chlorine radical (Cl), an extremely potent oxidant that can be released in the morning in chloride-rich environments as a result of nocturnal build-up of nitryl chloride (ClNO2). Chloride makes up a higher percentage of particulate matter in Delhi than has been observed anywhere else in the world, which results in Cl having an unusually strong influence in this city. Here, we present observations and model results revealing that atmospheric chemistry in Delhi exhibits an unusual diel cycle that is controlled by high concentrations of NO during the night. As a result of this, the formation of both NO3 and dinitrogen pentoxide (N2O5), a precursor of ClNO2 and thus Cl, are suppressed at night and increase to unusually high levels during the day. Our results indicate that a substantial reduction in nighttime NO has the potential to increase both nocturnal oxidation via NO3 and the production of Cl during the day.

  DOI

• Heterogeneous Nitrate Production Mechanisms in Intense Haze Events in the North China Plain

  Journal of Geophysical Research Atmospheres · 2021 · 82 citations

  • Environmental science
  • Atmospheric sciences
  • Environmental chemistry

  Abstract Studies of wintertime air quality in the North China Plain (NCP) show that particulate‐nitrate pollution persists despite rapid reduction in NO x emissions. This intriguing NO x ‐nitrate relationship may originate from non‐linear nitrate‐formation chemistry, but it is unclear which feedback mechanisms dominate in NCP. In this study, we re‐interpret the wintertime observations of 17 O excess of nitrate (∆ 17 O(NO 3 − )) in Beijing using the GEOS‐Chem (GC) chemical transport model to estimate the importance of various nitrate‐production pathways and how their contributions change with the intensity of haze events. We also analyze the relationships between other metrics of NO y chemistry and [PM 2.5 ] in observations and model simulations. We find that the model on average has a negative bias of −0.9‰ and −36% for ∆ 17 O(NO 3 − ) and [O x,major ] (≡ [O 3 ] + [NO 2 ] + [p‐NO 3 − ]), respectively, while overestimating the nitrogen oxidation ratio ([NO 3 − ]/([NO 3 − ] + [NO 2 ])) by +0.12 in intense haze. The discrepancies become larger in more intense haze. We attribute the model biases to an overestimate of NO 2 ‐uptake on aerosols and an underestimate in wintertime O 3 concentrations. Our findings highlight a need to address uncertainties related to heterogeneous chemistry of NO 2 in air‐quality models. The combined assessment of observations and model results suggest that N 2 O 5 uptake in aerosols and clouds is the dominant nitrate‐production pathway in wintertime Beijing, but its rate is limited by ozone under high‐NO x ‐high‐PM 2.5 conditions. Nitrate production rates may continue to increase as long as [O 3 ] increases despite reduction in [NO x ], creating a negative feedback that reduces the effectiveness of air pollution mitigation.

  DOI

• Global tropospheric halogen (Cl, Br, I) chemistry and its impact on oxidants

  Atmospheric chemistry and physics · 2021 · 195 citations

  • Chemistry
  • Atmospheric sciences
  • Physical chemistry

  Abstract. We present an updated mechanism for tropospheric halogen (Cl + Br + I) chemistry in the GEOS-Chem global atmospheric chemical transport model and apply it to investigate halogen radical cycling and implications for tropospheric oxidants. Improved representation of HOBr heterogeneous chemistry and its pH dependence in our simulation leads to less efficient recycling and mobilization of bromine radicals and enables the model to include mechanistic sea salt aerosol debromination without generating excessive BrO. The resulting global mean tropospheric BrO mixing ratio is 0.19 ppt (parts per trillion), lower than previous versions of GEOS-Chem. Model BrO shows variable consistency and biases in comparison to surface and aircraft observations in marine air, which are often near or below the detection limit. The model underestimates the daytime measurements of Cl2 and BrCl from the ATom aircraft campaign over the Pacific and Atlantic, which if correct would imply a very large missing primary source of chlorine radicals. Model IO is highest in the marine boundary layer and uniform in the free troposphere, with a global mean tropospheric mixing ratio of 0.08 ppt, and shows consistency with surface and aircraft observations. The modeled global mean tropospheric concentration of Cl atoms is 630 cm−3, contributing 0.8 % of the global oxidation of methane, 14 % of ethane, 8 % of propane, and 7 % of higher alkanes. Halogen chemistry decreases the global tropospheric burden of ozone by 11 %, NOx by 6 %, and OH by 4 %. Most of the ozone decrease is driven by iodine-catalyzed loss. The resulting GEOS-Chem ozone simulation is unbiased in the Southern Hemisphere but too low in the Northern Hemisphere.

  DOI

• Rapid cloud removal of dimethyl sulfide oxidation products limits SO ₂ and cloud condensation nuclei production in the marine atmosphere

  Proceedings of the National Academy of Sciences · 2021 · 100 citations

  • Atmospheric sciences
  • Environmental science
  • Chemistry

  concentrations over the ocean are lowered by 24%. This large, previously unconsidered loss process for volatile sulfur accelerates the timescale for the conversion of DMS to sulfate while limiting new particle formation in the marine atmosphere and changing the dynamics of aerosol growth. This loss process potentially reduces the spatial scale over which DMS emissions contribute to aerosol production and growth and weakens the link between DMS emission and marine CCN production with subsequent implications for cloud formation, radiative forcing, and climate.

  DOI

• Quantification of organic aerosol and brown carbon evolution in fresh wildfire plumes

  Proceedings of the National Academy of Sciences · 2020 · 282 citations

  • Environmental science
  • Atmospheric sciences
  • Environmental chemistry

  ) measured in the first few hours of plume evolution, despite accounting for just 4 ± 2% of average OA mass. These measurements provide quantitative constraints on the role of dilution-driven evaporation of OA and subsequent radical-driven oxidation on the fate of biomass-burning OA and BrC in daytime wildfire plumes and point to the need to understand how processing of nighttime emissions differs.

  DOI

• Thank You to Our 2019 Peer Reviewers

  Geophysical Research Letters · 2020 · 17 citations

  • Computer Science
  • Political Science
  • Library science

  Abstract On behalf of the journal, AGU, and the scientific community, the editors would like to sincerely thank those who reviewed the manuscripts for Geophysical Research Letters in 2019. The hours reading and commenting on manuscripts not only improve the manuscripts but also increase the scientific rigor of future research in the field. We particularly appreciate the timely reviews in light of the demands imposed by the rapid review process at Geophysical Research Letters . With the revival of the “major revisions” decisions, we appreciate the reviewers' efforts on multiple versions of some manuscripts. With the advent of AGU's data policy, many reviewers have helped immensely to evaluate the accessibility and availability of data associated with the papers they have reviewed, and many have provided insightful comments that helped to improve the data presentation and quality. We greatly appreciate the assistance of the reviewers in advancing open science, which is a key objective of AGU's data policy. Many of those listed below went beyond and reviewed three or more manuscripts for our journal, and those are indicated in italics.

  DOI

• HONO Emissions from Western U.S. Wildfires Provide Dominant Radical Source in Fresh Wildfire Smoke

  Environmental Science & Technology · 2020 · 144 citations

  • Environmental science
  • Environmental chemistry
  • Meteorology

  ) in early stage (<3 h) wildfire plume evolution. These results highlight the role of HONO as a major component of reactive nitrogen emissions from wildfires and the main driver of initial photochemical oxidation.

  DOI

Frequent coauthors

• Markku Kulmala

  University of Helsinki

  13 shared

• Claudia Mohr

  Board of the Swiss Federal Institutes of Technology

  11 shared

• Varun Kumar

  Paul Scherrer Institute

  7 shared

• David R. Hadden

  6 shared

• Sophie L. Haslett

  Stockholm University

  6 shared

• Wei Ma

  Beijing University of Chemical Technology

  5 shared

• Andrê S. H. Prévôt

  5 shared

• Yongchun Liu

  Beijing University of Chemical Technology

  5 shared

Awards & honors

• 2018 American Geophysical Union Ascent Award, "For outstandi…
• 2012 Henry G Houghton Award, American Meteorological Society
• 2010 Annual Teaching Award, Department of Atmospheric Scienc…
• 2009 NSF CAREER Award
• 2004 NASA New Investigator Service

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