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Upcoming Seminars
| Title: | Global analysis of halogenated trace gases in the UTLS: From
long-lived to short-lived substances
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| Speaker: |
Markus Jesswein
Markus Jesswein received his Ph.D from the Institute for Atmospheric and
Environmental Sciences at Goethe University Frankfurt, Germany. During his time as a
doctoral student and subsequently as a postdoctoral researcher, he participated in two
aircraft measurement campaigns with the German scientific aircraft HALO and worked
with a two-channel in-situ instrument (GhOST). He is also very interested in
programming and modeling. This includes writing various Python tools and, most
recently, working with the Lagrangian transport and dispersion model FLEXPART.
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| Date/Time: |
Thursday, January 22, 2026 01:00 PM MST (-0700)
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| Location: |
David Skaggs Research Center, Room GC402
Google Meet |
Abstract
This talk examines the distribution of chlorinated and brominated substances in the
upper troposphere and lower stratosphere (UTLS), focusing on their role in
stratospheric ozone depletion. Although long-lived halogenated compounds have
declined as a result of the Montreal Protocol, short-lived substances - some natural and
some anthropogenic - are unregulated and are increasingly significant in the
stratospheric halogen budget.
Airborne observations were made using the GhOST instrument aboard the HALO
aircraft during the 2019 SouthTRAC campaign over the Antarctic. These measurements
revealed that inorganic chlorine (Cly) reached up to 1687 ± 19 ppt at 385 K within the
polar vortex, representing ~50% of total chlorine there, compared to ~40% in the Arctic
under similar conditions. The Antarctic vortex contained ~540 ppt more Cly than the
Arctic vortex in this comparison.
Moving from long-lived to short-lived substances, the distribution of key short-lived
brominated substances, CH₂Br₂ and CHBr₃, was analyzed using data from several
international campaigns. CH₂Br₂ showed clear seasonality, especially in the Northern
Hemisphere, while CHBr₃ was more variable. Lower concentrations of both substances
in the Southern Hemisphere autumn suggest less efficient troposphere-to-stratosphere
transport. Model comparisons (TOMCAT and CAM-Chem) revealed inconsistencies,
particularly in reproducing Southern Hemisphere seasonality and bromine variability,
highlighting the need for improved modeling and more observational data, especially in
the Southern Hemisphere.
Lastly, investigations of how short-lived chlorinated pollutants, specifically CH₂Cl₂, are
transported from the Asian Summer Monsoon (ASM) region to the upper troposphere
and lower stratosphere were carried out. Using aircraft measurements from the 2023
PHILEAS campaign and FLEXPART transport modeling, it was found that strong
convection in the East Asian Summer Monsoon (EASM) lifted polluted air to the
subarctic upper troposphere, bypassing the usual ASM anticyclone pathways. Although
the direct entry of these pollutants into the stratosphere was small, such events can
contribute to increasing background levels over time.
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| Title: | Reduced U.S. Methane Emissions during the COVID-19 Pandemic
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| Speaker: |
Sergio Ibarra Espinosa
Sergio's career is defined by overcoming challenges through persistent effort. From
funding his own education at age seven to developing complex scientific software, his
focus has always been forward. He is the creator of the popular VEIN emissions model
and has built multiple open-source tools for greenhouse gas modeling in R, Python, and
Fortran. He continues to pursue ambitious goals, now designing a novel real-time
emissions dashboard to unite science and policy in a single, powerful framework.
https://ibarraespinosa.github.io/. In his free time, Sergio researches South America, is a
dancer, musician, and cooker.
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| Date/Time: |
Thursday, January 22, 2026 01:00 PM MST (-0700)
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| Location: |
David Skaggs Research Center, Room GC402
Google Meet |
Abstract
The coronavirus disease 2019 (COVID-19) pandemic disrupted normal human activities
worldwide, and mobility restrictions resulted in reduced levels of air pollutants and
greenhouse gas emissions. Here, we examine the impact of these disruptions on a
potent greenhouse gas, methane (CH 4 ), over the U.S. In this study, we quantified CH 4
emissions from the contiguous U.S. between 2019 and 2021 by analyzing inverse
modeling results derived from atmospheric measurements made at 35 sites across the
country. Our estimates indicate emission reductions of -2.5 (standard deviation of
anomalies -3.2 to -2.1 among our ensemble members) Tgy -1 CH 4 in 2020 and -2.9 (-5.2
to -0.4) Tgy -1 in 2021, relative to 2019. The respective percentage change was a -4.3 (-
5.1 to -3.5)% reduction in 2020 and -4.8 (-8.3 to -0.7) % in 2021, relative to 2019.
Combining with process-based inventory emission datasets, we found that this
reduction was primarily due to decreased fossil fuel and agricultural emissions;
however, record-breaking forest fires resulted in an increase of 0.4 (0.1 to 0.8) Tgy⁻¹ in
2020-2019, equal to a 20 (2.9 to 46)% increase in CH 4 emissions from the western U.S.
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