
My research group studies how aerosol formation and the oxidative capacity of the atmosphere change in response to both climate change and anthropogenic activities. We aim to answer two fundamental questions in atmospheric chemistry:
1.How do the formation pathways of sulfate and nitrate aerosols vary over space and time, and what are the implications for atmospheric chemistry and climate?
2.How has the oxidation capacity of the atmosphere changed in response to both anthropogenic and climate forcing, and what are the implications for climate feedback processes via the impact on the concentration of reduced trace gases (e.g. CH4) that affect the distribution of energy in the climate system?
The main approaches that we use to answer the above questions are:
1.Measuring the isotopic composition of sulfate and nitrate from aerosol, water, snow, and ice core samples (see our laboratory facilities).
2.Modeling using global three-dimensional models of atmospheric chemistry and climate (mostly GEOS-Chem).
- Paleoclimate
- Atmospheric chemistry
- Aerosols
- Stable isotope geochemistry
- ATMOS 358: “Fundamentals of Atmospheric Chemistry” (Spring 2017)
- ATMOS 451 “Instruments and Observations” (last taught Winter 2017)
- ATMOS 220 “Exploring the Atmospheric and Climate Science” (last taught Winter 2017)
- ATMOS 212 “Air pollution: From Urban Smog to the Ozone Hole” (last taught Autumn 2016)
- ATMOS 523 “Seminar on Atmospheric Physics and Chemistry” (last organized Winter 2016)
- ATMOS 211 “Climate and Climate Change” (last taught Autumn 2015)
- ATMOS 558 “Atmospheric Chemistry” (last taught Spring 2013)
- ATMOS 520 “Atmospheric and Climate Science Colloquium” (last organized Spring 2012)
- ATMOS 458 “Global Atmospheric Chemistry” (last taught Autumn 2010)
- ATMOS 340 “Thermodynamics and Cloud Processes” (last taught Winter 2009)
- ATMOS/OCE/ESS 554 “Paleoclimate Proxies” (last taught Fall 2007 with Julian Sachs)
- ATMOS/OCE/ESS 588 “The Global Carbon Cycle and Greenhouse Gases” (last taught Spring 2006 with Steve Emerson)
- University of Washington ADVANCE Professor 2005
- NOAA CGC Postdoctoral Fellow 2003 – 2004
- Daly Postdoctoral Fellow, Harvard University, 2003 – 2004
- Invited ACCESS (Atmospheric Chemistry Conference for Emerging Senior Scientists) Participant 2003
- U.S. Environmental Protection Agency STAR Fellow 2000 – 2002
- Participant, AMS/UCAR Summer Policy Colloquium, Washington, D.C., June 2001
- U.S. Department of Education GAAN Fellow 1997 – 2000
- McGregory Fellowship in Chemistry, Colgate University, 1997
- Phi Eta Sigma Research Council Award, Colgate University, 1996
- WITCO Chemical Corporation Scholarship, Colgate University 1996
- Lila and Curtiss Frank Scholarship, Colgate University, 1995
- Associate Chair, Department of Atmospheric Sciences
- Undergraduate Program Coordinator, Department of Atmospheric Sciences
- Director, UW Program on Climate Change
- Member, Ice core Working Group
- Member, GEOS-Chem Steering Committee
- Co-Chair, GEOS-Chem Aerosols Working Group
Wang, X., D.J. Jacob, W. Downs, S. Zhai, L. Zhu, V. Shah, C.D. Holmes, T. Sherwen, B. Alexander, M.J. Evans, S.D. Eastham, J.A. Neuman, P. Veres, T.K. Koenig, R. Volkamer, L.G. Huey, T.J. Bannan, C.J. Percival, B.H. Lee, and J.A. Thornton, Global tropospheric halogen (Cl, Br, I) chemistry and its impact on oxidants, Atmos. Chem. Phys., 21, 13973-13996, doi:10.5194/acp-21-13973-2021 (2021).
Tilgner, Andreas, Thomas Schaefer, Becky Alexander, Mary Barth, Jeffrey L. Collett, Jr., Kathleen M. Fahey, Athanasios Nenes, Havala O. T. Pye, Hartmut Herrmann, and V. Faye McNeill, Acidity and the multiphase chemistry of atmospheric aqueous particles and clouds, Atmos. Chem. Phys., 21, 13483-13536, https://doi.org/10.5194/acp-21-13483-2021 (2021).
Jiang, Z., B. Alexander, J. Savarino, J. Erbland, and L. Geng, Impacts of the photo-driven post-depositional processing on snow nitrate and its isotopes at Summit, Greenland: a model-based study, The Cryosphere, 15, 4207-4220 (2021).
Zhai, S., X. Wang, J.R. McConnell, L. Geng, J. Cole-Dai, N. Chellman, T. Sherwen, R. Pound, K. Fujita, S. Hattori, J.M. Moch, L. Zhu, M.J. Evans, M. Legrand, P. Liu, D. Pasteris, Y.-C. Chan, L.T. Murray, and Becky Alexander, Anthropogenic impacts on tropospheric reactive chlorine since the preindustrial, Geophys. Res. Lett. 48 (14), e2021GL093808, doi: 10.1029/2021GL093808 (2021).
Hattori, S., Y. Iizuka, B. Alexander, S. Ishino, K. Fujita, S. Zhai, T. Sherwen, N. Oshima, R. Uemura, A. Yamada, N. Suzuki, S. Matoba, A. Tsuruta, J. Savarino, and N. Yoshida, Isotopic evidence for acidity-driven enhancement of sulfate formation after SO2 emission control, Science Adv., 7(19), eabd4610, doi:10.1126/sciadv.abd4610 (2021). UW press release.
Chan, Y.C., M.J. Evans, P. He, C.D. Holmes, L. Jaegle, P. Kasibhatla, X.-Y. Liu, T. Sherwen, J.A. Thornton, X. Wang, Z. Xie, S. Zhai, and B. Alexander, Heterogeneous nitrate production mechanisms in intense haze events in North China, J. Geophys. Res., e2021JD034688, doi:10.1029/2021JD034688 (2021).
Alexander, B., T. Sherwen, C.D. Holmes, J.A. Fisher, Q. Chen, M.J. Evans, and P. Kasibhatla, Global inorganic nitrate production mechanisms: Comparison of a global model with nitrate isotope observations, Atmos. Chem. Phys., 20, 3859-3877, https://doi.org/10.5194/acp-20-3859-2020 (2020).
Horowitz, H.; C.D. Holmes; A. Wright; T. Sherwen, M. Evans; J. Huang, L. Jaeglé, Q. Chen; and B. Alexander, Effects of sea salt aerosol emissions for Marine Cloud Brightening on atmospheric chemistry: Implications for radiative forcing, Geophys. Res. Lett., 47, e2019GL085838, https://doi.org/10.1029/2019GL085838 (2020).