The Department of Atmospheric Sciences Seminar is designed to inform students through
the presentation of scholarly works of students, faculty, staff and external scientists.
Videos of past seminars can be viewed on our YouTube channel here.
In-person seminars are at 3:00 pm in INSCC room 110.
March 6, 2024 - No Seminar - spring break
March 13, 2024 - Rachel Edie
March 20, 2024 - Karlie Rees
March 27, 2024 - Cristian Proistosescu, Department of Atmospheric Sciences and Department of Geology, University of Illinois
Title: The "Pattern Effect": How sea surface temperature patterns modulate radiative feedbacks and climate sensitivity
April 3, 2024 - William Ying-Hwa Kuo, Director of UCAR Community Programs, University Corporation for Atmospheric Research, Boulder, Colorado
April 10, 2024 - Hannah Horowitz
April 17, 2024 - Ramón Barthelemy, Department of Physics, University of Utah
Title: Sex and Gender Based Harassment in Physics and Astronomy
Abstract: Sex and gender based harassment are prevalent across academia as a whole, but also within the STEM fields. The field of physics has a well-documented history of discrimination against women and other groups, with the term sexual harassment being coined when describing the behavior of a Cornell physics faculty member in the 1970’s. This talk will discuss the current data on sex and gender based harassment in STEM and a longitudinal 10-year study on the experiences of graduate women in physics who are now professionals in the field. The talk will conclude with actions and steps everyone can take to make STEM a better place.
January 10, 2024 - Cassandra Gaston, Assistant Professor, Dept. of Atmospheric Sciences, Rosenstiel School of Marine
and Atmospheric Sciences University of Miami
Title: PlayaDustEffectsonAtmospheric Halogens and Air Quality
Abstract: Wintertime secondary pollutants, such as ground-level ozone and secondary particulate matter, is a major problem in the western United States whose formation mechanisms are poorly understood. A possible explanation for this phenomenon is the production of chlorine radicals that are thought to originate from the photolysis of nitryl chloride (ClNO2), formed when dinitrogen pentoxide (N2O5) reacts with chloride-containing aerosol. One aspect of this hypothesis that has puzzled the atmospheric chemistry community is, where does the aerosol chloride come from especially in regions far from the ocean? In this talk, I will provide evidence that an underexplored, inland source of chlorine radicals is from saline playas (e.g., dried lakebeds), including the shrinking Great Salt Lake. Playas emit large quantities of dust, and our laboratory studies, using playa material from different regions of the south and southwestern United States, showed that playa dust can interact with N2O5 and efficiently produce ClNO2. We attempted to predict our laboratory results using current parameterizations of reactive chlorine chemistry that rely on bulk measurements of particulate chloride and predictions of aerosol liquid content, but consistently overpredicted our results. By performing detailed bulk and single-particle analysis on different playa dust samples, we found that playa dust mineralogy, particularly at the particle surface, determines the reactivity of these dusts with N2O5 rather than bulk aerosol chloride content. We have extended our exploratory results to focus on regional emissions of dust from the Great Salt Lake and find that dust emitted from the Northern and Southern arms of the basin have vastly different reactivities and potentials to generate ClNO2, which also is likely due to differences in dust mineralogy. Because both climate change and water use practices are predicted to increase the geographic extent of playas worldwide, this work has implications for current and future air quality considerations.
January 17, 2024 - Kerri Pratt, Department of Earth & Environmental Science, University of Michigan
Title: Observations & Modeling of Wintertime Atmospheric Chlorine Chemistry: Connections to Snow & Road Salt
Abstract: Recent laboratory and computational chemistry studies have shown that N2O5 reacts at the atmospheric particle surface, with ClNO2 produced from chloride-containing particles. However, multiphase reactions are typically simulated using mass-based chemical composition, which assumes homogeneous distribution of chemical components across all particles with complete surface availability for reaction. We developed a new approach to parametrize N2O5 uptake and ClNO2 yield that considers the heterogeneity of the aerosol population and applied this in three wintertime environments – Ann Arbor, MI, Kalamazoo, MI, and East Boothbay, ME. Single-particle mass spectrometry and electron microscopy with energy-dispersive X-ray spectroscopy measured single-particle composition and showed that only a fraction of the particulate surface area in each study contained chloride. We assigned N2O5 uptake and ClNO2 yield values to each particle type, based on lab-based aerosol proxy data, and weighted these by particle surface area. This new approach more accurately simulated ClNO2, compared to existing methods that frequently overestimate ClNO2 production. In the inland, wintertime environment, road salt aerosol was identified as a dominant chloride aerosol source, with uncertainties remaining in the contribution from residential wood burning aerosols. This new single-particle-based parameterization is expected to be applicable to other multiphase reactions that occur at the particle surface. In addition, we showed through outdoor chamber studies and gradient flux measurements that the saline snowpack is also an important source of ClNO2 in the wintertime urban environment.
January 24, 2024 - Atmospheric Sciences graduate students
Meet grad students and learn about their research!
January 31, 2024 - Summer Rupper, Professor, Department of Geography, University of Utah
Title: Tapping into Spy Satellite Imagery to Measure Glacier Change and Sensitivity to Climate in the Water Towers of Asia
Abstract: The high mountain regions of Asia are host to more snow and ice than anywhere outside of the Polar Regions. Changes in snow and ice storage in these remote landscapes have the potential to impact the nearly 1 billion people living downstream. While it is clear that glaciers are generally retreating globally, there is a significant paucity of data on glacier changes in high-mountain Asia. These glacial systems are extremely remote, occur at very high altitudes, and are often located along disputed borders in geopolitically unstable regions. This has hampered our understanding of these systems, the mechanisms driving the changes, and the downstream impacts. Here we tap into historical spy satellite imagery to measure the change in glacier volume across the Himalayan range over the past ~50 years, filling in critical temporal and spatial gaps in glacier observations and glacier response to climate. We then use these data to reevaluate (1) glacier sensitivity to climate change and (2) the potential to use glacier observations as a climate proxy over the modern era.
February 14, 2024 - No seminar - special seminar February 15, 11:00 am
February 21, 2024 - Daniel Baldassare Ph.D. Defense
Title: Improved Estimates of the Hadley Cell in the Past, Present, and Future
February 28, 2024 - Manvendra Dubey, Ph.D., Los Alamos National Laboratory
Title: Greenhouse Gases Observations 1957-2100: Past, Present & Future
Abstract: Dr. David Charles Keeling’s precise CO2 observations at the remote Mauna Loa site discerned its global rise that is attributed to emissions from human activities. His Keeling curve built the observational framework to examine anthropogenic climate change that has expanded to encompass other greenhouse gases (GHG) and monitoring modalities. The accelerating GHG rise and the heat absorbed by them led to concerns about climate change that continue to exacerbate with time.
My lecture will:
- Trace how multiple long-term atmospheric CO2 observations (in situ surface, and total column from ground and satellites) have helped quantify that vegetation and ocean soak up half of the human CO2 emissions and elucidate regional fluxes (national to Amazon).
- Describe international agreements that slowed the rise of halocarbons and strengthening policies to reduce CH4, CO2 and N2O emissions. Highlight how novel CH4 observations are helping constrain emissions (at Four Corners, dairies, cities, and oil and gas plays)
- Discuss the future trajectory of CO2 and monitor efficacy of decarbonizing efforts and carbon credits. Stress that positive carbon-climate feedback pose a risk, and their early detection will be key to accelerate decarbonization at scale.
Seminars from earlier semesters are listed here.