• Affiliate Scientist, National Center for Atmospheric Research
  • Professor, Atmospheric Sciences

Research Statement

The overarching theme of Dr. Hallar's research is using high quality measurements of trace gases, aerosol physical and chemical properties, and cloud microphysics to understand connections between the biosphere, atmosphere, and climate, along with the impact of anthropogenic emissions on these connections. More specifically, currently her research uses high elevation sites, combined with airborne measurements, to study the formation processes of Cloud Condensation Nuclei and Ice Nuclei.



  • Hallar, A.G., S. Lance, J. Lin, D. Jaffe, Need for Mountain Observatories for Composition of the Atmosphere (MOCA) Network in U.S., American Geophysical Union Meeting, San Francisco, CA, December, 11, 2019. Invited Talk/Keynote, Presented, 12/11/2019.


  • Hallar AG, Brown SS, Crosman E, Barsanti K, Cappa CD, Faloona I, Fast J, Holmes HA, Horel J, Lin J, Middlebrook A, Mitchell L, Murphy J, Womack CC, Aneja V, Baasandorj M, Bahreini R, Banta R, Bray C, Brewer A, Caulton D & de Gouw J (2021). Coupled Air Quality and Boundary-Layer Meteorology in Western U.S. Basins during Winter: Design and Rationale for a Comprehensive Study. Bulletin of the American Meteorological Society. Vol. 0, 1-94. Published, 08/01/2021.
  • Lowenthal, D. H., Hallar, A. G., David, R. O., McCubbin, I. B., Borys, R. D., and Mace, G. G.: Mixed-phase orographic cloud microphysics during StormVEx and IFRACS, Atmos. Chem. Phys., 19, 5387-5401,, 2019. Published, 04/24/2019.
  • Ross C. Petersen, Anna G. Hallar, Ian B. McCubbin, John A. Ogren, Elisabeth Andrews, Douglas Lowenthal, Riley Gorder, Rick Purcell, Darrah Sleeth & Igor Novosselov (2019) Numerical, wind-tunnel, and atmospheric evaluation of a turbulent ground-based inlet sampling system, Aerosol Science and Technology, DOI: 10.1080/02786826.2019.1602718. Accepted, 03/07/2019.
  • Andrews E., Sheridan P., Ogren J., Hageman D., Jefferson A., Wendell J., Alástuey A., Alados-Arboledas L., Bergin M., Ealo M., Gannet Hallar A., Hoffer A., Kalapov I., Keywood M., Kim J., Kim S., Kolonjari F., Labuschagne C., Lin N., Macdonald A., Mayol-Bracero O., McCubbin I., Pandolfi M., Reisen F., Sharma S., Sherman J., Sorribas M. & Sun J. (2019). Overview of the NOAA/ESRL federated aerosol network. (pp. 123-135). Vol. 100. Bulletin of the American Meteorological Society. Published, 01/01/2019.
  • Coen M., Andrews E., Aliaga D., Andrade M., Angelov H., Bukowiecki N., Ealo M., Fialho P., Flentje H., Gannet Hallar A., Hooda R., Kalapov I., Krejci R., Lin N., Marinoni A., Ming J., Nguyen N., Pandolfi M., Pont V., Ries L., Rodríguez S., Schauer G., Sellegri K., Sharma S., Sun J., Tunved P., Velasquez P. & Ruffieux D. (2018). Identification of topographic features influencing aerosol observations at high altitude stations. (pp. 12289-12313). Vol. 18. Atmospheric Chemistry and Physics. Published, 08/24/2018.
  • Kassianov E. , M. Pekour, C. Flynn, L.K. Berg, J. Beranek, A. Zelenyuk, C. Zhao, L.R. Leung, P.L. Ma, J. Barnard, A.G. Hallar, I.B. McCubbin, E.W. Eloranta, A. McComiskey & P.J. Rasch (2017). Large Contribution of Coarse Mode to Aerosol Microphysical and Optical Properties: Evidence from Ground-based Observations of a Trans-Pacific Asian Dust Outbreak at a High-Elevation North American Site. Journal of Atmospheric Sciences. Vol. 75, 1431-1443. Published, 05/01/2017.
  • Taylor N., Collins D., Lowenthal D., McCubbin I., Gannet Hallar A., Samburova V., Zielinska B., Kumar N. & Mazzoleni L. (2017). Hygroscopic growth of water soluble organic carbon isolated from atmospheric aerosol collected at US national parks and Storm Peak Laboratory. (pp. 2555-2571). Vol. 17. Atmospheric Chemistry and Physics. Published, 02/20/2017.
  • Hallar A., Molotch N., Hand J., Livneh B., McCubbin I., Petersen R., Michalsky J., Lowenthal D. & Kunkel K. (2017). Impacts of increasing aridity and wildfires on aerosol loading in the intermountain Western US. Vol. 12. Environmental Research Letters. Published, 01/01/2017.
  • Sullivan R., Crippa P., Hallar A., Clarisse L., Whitburn S., Van Damme M., Leaitch W., Walker J., Khlystov A. & Pryor S. (2016). Using satellite-based measurements to explore spatiotemporal scales and variability of drivers of new particle formation. (pp. 12,217-12,235). Vol. 121. Journal of Geophysical Research. Published, 10/27/2016.
  • Lowenthal, D., Hallar, A.G., McCubbin, I., David, R., Borys, R., Blossey, P., Muhlbauer, A., Kuang, Z. and Moore,M., 2016. Isotopic Fractionation in Wintertime Orographic Clouds. Journal of Atmospheric and Oceanic Technology, 33(12), pp.2663-2678. Published, 10/01/2016.
  • Hallar, A.G. E. Andrews, N. Bukowiecki, D. A. Jaffe, N-H Lin, 2016: Overview of the Special Issue “Selected Papers from the 2nd Atmospheric Chemistry and Physics at Mountain Sites Symposium” Aerosol and Air Quality Research, Volume 16, No. 3, March 2016, Pages 471-477, doi: 10.4209/aaqr.2016.02.0077. Published, 08/22/2016.
  • Yu F., Luo G. & Hallar A. (2016). Vertical profiles and seasonal variations of key parameters controlling particle formation and growth at storm peak laboratory. (pp. 900-908). Vol. 16. Aerosol and Air Quality Research. Published, 03/01/2016.
  • Hallar A., Petersen R., McCubbin I., Lowenthal D., Lee S., Andrews E. & Yu F. (2016). Climatology of new particle formation and corresponding precursors at storm peak laboratory. (pp. 816-826). Vol. 16. Aerosol and Air Quality Research. Published, 03/01/2016.
  • Lowenthal D., Hallar A., McCubbin I., David R., Borys R., Blossey P., Muhlbauer A., Kuang Z. & Moore M. (2016). Isotopic fractionation in wintertime orographic clouds. (pp. 2663-2678). Vol. 33. Journal of Atmospheric and Oceanic Technology. Published, 01/01/2016.
  • Yu F., Luo G., Pryor S., Pillai P., Lee S., Ortega J., Schwab J., Hallar A., Leaitch W., Aneja V., Smith J., Walker J., Hogrefe O. & Demerjian K. (2015). Spring and summer contrast in new particle formation over nine forest areas in North America. (pp. 13993-14003). Vol. 15. Atmospheric Chemistry and Physics. Published, 12/18/2015.
  • Hallar A., Petersen R., Andrews E., Michalsky J., McCubbin I. & Ogren J. (2015). Contributions of dust and biomass burning to aerosols at a Colorado mountain-top site. (pp. 13665-13679). Vol. 15. Atmospheric Chemistry and Physics. Published, 12/10/2015.
  • Kristensen T., Du L., Nguyen Q., Nøjgaard J., Bender Koch C., Faurskov Nielsen O., Hallar A., Lowenthal D., Nekat B., Van Pinxteren D., Herrmann H., Glasius M., Kjaergaard H. & Bilde M. (2015). Chemical properties of HULIS from three different environments. (pp. 65-80). Vol. 72. Journal of Atmospheric Chemistry. Published, 01/01/2015.
  • Yu F. & Hallar A. (2014). Difference in particle formation at a mountaintop location during spring and summer: Implications for the role of sulfuric acid and organics in nucleation. (pp. 12246-12255). Vol. 119. Journal of Geophysical Research Atmospheres. Published, 11/16/2014.
  • Yu H., Gannet Hallar A., You Y., Sedlacek A., Springston S., Kanawade V., Lee Y., Wang J., Kuang C., McGraw R., McCubbin I., Mikkila J. & Lee S. (2014). Sub-3 nm particles observed at the coastal and continental sites in the United States. (pp. 860-879). Vol. 119. Journal of Geophysical Research Atmospheres. Published, 01/27/2014.
  • Zhao Y., Hallar A. & Mazzoleni L. (2013). Atmospheric organic matter in clouds: Exact masses and molecular formula identification using ultrahigh-resolution FT-ICR mass spectrometry. (pp. 12343-12362). Vol. 13. Atmospheric Chemistry and Physics. Published, 12/18/2013.
  • Friedman B., Zelenyuk A., Beranek J., Kulkarni G., Pekour M., Gannet Hallar A., McCubbin I., Thornton J. & Cziczo D. (2013). Aerosol measurements at a high-elevation site: Composition, size, and cloud condensation nuclei activity. (pp. 11839-11851). Vol. 13. Atmospheric Chemistry and Physics. Published, 12/09/2013.
  • Samburova V., Gannet Hallar A., Mazzoleni L., Saranjampour P., Lowenthal D., Kohl S. & Zielinska B. (2013). Composition of water-soluble organic carbon in non-urban atmospheric aerosol collected at the Storm Peak Laboratory. (pp. 370-380). Vol. 10. Environmental Chemistry. Published, 11/08/2013.
  • Avallone L., Hallar A., Thiry H. & Edwards L. (2013). Supporting the retention and advancement of women in the atmospheric sciences: What women are saying. (pp. 1313-1316). Vol. 94. Bulletin of the American Meteorological Society. Published, 09/01/2013.
  • Amin H., Russo R., Sive B., Richard Hoebeke E., Dodson C., McCubbin I., Gannet Hallar A. & Huff Hartz K. (2013). Monoterpene emissions from bark beetle infested Engelmann spruce trees. (pp. 130-133). Vol. 72. Atmospheric Environment. Published, 06/01/2013.
  • Berg A., Heald C., Huff Hartz K., Hallar A., Meddens A., Hicke J., Lamarque J. & Tilmes S. (2013). The impact of bark beetle infestations on monoterpene emissions and secondary organic aerosol formation in western North America. (pp. 3149-3161). Vol. 13. Atmospheric Chemistry and Physics. Published, 04/08/2013.
  • Asmi A., Collaud Coen M., Ogren J., Andrews E., Sheridan P., Jefferson A., Weingartner E., Baltensperger U., Bukowiecki N., Lihavainen H., Kivekäs N., Asmi E., Aalto P., Kulmala M., Wiedensohler A., Birmili W., Hamed A., O'Dowd C., Jennings S., Weller R., Flentje H., Fjaeraa A., Fiebig M., Myhre C., Hallar A., Swietlicki E., Kristensson A. & Laj P. (2013). Aerosol decadal trends-Part 2: In-situ aerosol particle number concentrations at GAW and ACTRIS stations. (pp. 895-916). Vol. 13. Atmospheric Chemistry and Physics. Published, 02/01/2013.
  • Matrosov S., Mace G., Marchand R., Shupe M., Hallar A. & Mccubbin I. (2012). Observations of ice crystal habits with a scanning polarimetric W-band radar at slant linear depolarization ratio mode. (pp. 989-1008). Vol. 29. Journal of Atmospheric and Oceanic Technology. Published, 08/01/2012.
  • Mazzoleni L., Saranjampour P., Dalbec M., Samburova V., Hallar A., Zielinska B., Lowenthal D. & Kohl S. (2012). Identification of water-soluble organic carbon in non-urban aerosols using ultrahigh-resolution FT-ICR mass spectrometry: Organic anions. (pp. 285-297). Vol. 9. Environmental Chemistry. Published, 07/10/2012.
  • Amin H, Atkins PT, Russo RS, Brown AW, Sive B, Hallar AG & Huff Hartz KE (2012). Effect of bark beetle infestation on secondary organic aerosol precursor emissions. Environmental science & technology. Vol. 46, 5696-703. Published, 06/01/2012.
  • Bowers R., McCubbin I., Hallar A. & Fierer N. (2012). Seasonal variability in airborne bacterial communities at a high-elevation site. (pp. 41-49). Vol. 50. Atmospheric Environment. Published, 04/01/2012.
  • Kristensen T., Wex H., Nekat B., Njgaard J., Van Pinxteren D., Lowenthal D., Mazzoleni L., Dieckmann K., Bender Koch C., Mentel T., Herrmann H., Gannet Hallar A., Stratmann F. & Bilde M. (2012). Hygroscopic growth and CCN activity of HULIS from different environments. Vol. 117. Journal of Geophysical Research Atmospheres. Published, 01/01/2012.
  • Baustian K., Cziczo D., Wise M., Pratt K., Kulkarni G., Hallar A. & Tolbert M. (2012). Importance of aerosol composition, mixing state, and morphology for heterogeneous ice nucleation: A combined field and laboratory approach. Vol. 117. Journal of Geophysical Research Atmospheres. Published, 01/01/2012.
  • Hallar A., Chirokova G., McCubbin I., Painter T., Wiedinmyer C. & Dodson C. (2011). Atmospheric bioaerosols transported via dust storms in the western United States. Vol. 38. Geophysical Research Letters. Published, 09/01/2011.
  • Hallar A., Lowenthal D., Chirokova G., Borys R. & Wiedinmyer C. (2011). Persistent daily new particle formation at a mountain-top location. (pp. 4111-4115). Vol. 45. Atmospheric Environment. Published, 08/01/2011.
  • Hallar A., McCubbin I. & Wright J. (2011). Change: A place-based curriculum for understanding climate change at Storm Peak Laboratory, Colorado. (pp. 909-918). Vol. 92. Bulletin of the American Meteorological Society. Published, 07/01/2011.
  • Hoyle C., Boy M., Donahue N., Fry J., Glasius M., Guenther A., Hallar A., Huff Hartz K., Petters M., Petäjä T., Rosenoern T. & Sullivan A. (2011). A review of the anthropogenic influence on biogenic secondary organic aerosol. (pp. 321-343). Vol. 11. Atmospheric Chemistry and Physics. Published, 01/21/2011.
  • Samy S., Mazzoleni L., Mishra S., Zielinska B. & Hallar A. (2010). Water-soluble organic compounds at a mountain-top site in Colorado, USA. (pp. 1663-1671). Vol. 44. Atmospheric Environment. Published, 04/01/2010.
  • Hallar A., McCubbin I., Hallar B., Levine R., Stockwell W., Lopez J. & Wright J. (2010). Science in the mountains: A unique research experience to enhance diversity in the geosciences. (pp. 95-100). Vol. 58. Journal of Geoscience Education. Published, 03/01/2010.
  • Strawa A., Kirchstetter T., Hallar A., Ban-Weiss G., McLaughlin J., Harley R. & Lunden M. (2010). Optical and physical properties of primary on-road vehicle particle emissions and their implications for climate change. (pp. 36-50). Vol. 41. Journal of Aerosol Science. Published, 01/01/2010.
  • Faïn X., Obrist D., Hallar A., McCubbin I. & Rahn T. (2009). High levels of reactive gaseous mercury observed at a high elevation research laboratory in the rocky mountains. (pp. 8049-8060). Vol. 9. Atmospheric Chemistry and Physics. Published, 11/30/2009.
  • Wiedinmyer C., Bowers R., Fierer N., Horanyi E., Hannigan M., Hallar A., McCubbin I. & Baustian K. (2009). The contribution of biological particles to observed particulate organic carbon at a remote high altitude site. (pp. 4278-4282). Vol. 43. Atmospheric Environment. Published, 09/01/2009.
  • Wekker S., Ameen A., Song G., Stephens B., Hallar A. & McCubbin I. (2009). A preliminary investigation of boundary layer effects on daytime atmospheric CO2 concentrations at a mountaintop location in the Rocky Mountains. (pp. 904-922). Vol. 57. Acta Geophysica. Published, 08/24/2009.
  • Bowers R., Lauber C., Wiedinmyer C., Hamady M., Hallar A., Fall R., Knight R. & Fierer N. (2009). Characterization of airborne microbial communities at a high-elevation site and their potential to act as atmospheric ice nuclei. (pp. 5121-5130). Vol. 75. Applied and Environmental Microbiology. Published, 08/01/2009.
  • Bowers RM, Lauber CL, Wiedinmyer C, Hamady M, Hallar AG, Fall R, Knight R & Fierer N (2009). Characterization of airborne microbial communities at a high-elevation site and their potential to act as atmospheric ice nuclei. Applied and environmental microbiology. Vol. 75, 5121-30. Published, 07/01/2009.
  • Obrist D., Hallar A., McCubbin I., Stephens B. & Rahn T. (2008). Atmospheric mercury concentrations at Storm Peak Laboratory in the Rocky Mountains: Evidence for long-range transport from Asia, boundary layer contributions, and plant mercury uptake. (pp. 7579-7589). Vol. 42. Atmospheric Environment. Published, 10/01/2008.
  • Davis S., Hallar A., Avallone L. & Engblom W. (2007). Measurement of total water with a tunable diode laser hygrometer: Inlet analysis, calibration procedure, and ice water content determination. (pp. 463-475). Vol. 24. Journal of Atmospheric and Oceanic Technology. Published, 03/01/2007.
  • Lopez J., Fridlind A., Jost H., Loewenstein M., Ackerman A., Campos T., Weinstock E., Sayres D., Smith J., Pittman J., Hallar A., Avallone L., Davis S. & Herman R. (2006). CO signatures in subtropical convective clouds and anvils during CRYSTAL-FACE: An analysis of convective transport and entrainment using observations and a cloud-resolving model. Vol. 111. Journal of Geophysical Research Atmospheres. Published, 05/16/2006.
  • Hallar A., Strawa A., Schmid B., Andrews E., Ogren J., Sheridan P., Ferrare R., Covert D., Elleman R., Jonsson H., Bokarius K. & Luu A. (2006). Atmospheric Radiation Measurements Aerosol Intensive Operating Period: Comparison of aerosol scattering during coordinated flights. Vol. 111. Journal of Geophysical Research Atmospheres. Published, 03/16/2006.
  • Strawa A., Elleman R., Hallar A., Covert D., Ricci K., Provencal R., Owano T., Jonsson H., Schmid B., Luu A., Bokarius K. & Andrews E. (2006). Comparison of in situ aerosol extinction and scattering coefficient measurements made during the Aerosol Intensive Operating Period. Vol. 111. Journal of Geophysical Research Atmospheres. Published, 03/16/2006.
  • Schmid B., Ferrare R., Flynn C., Elleman R., Covert D., Strawa A., Welton E., Turner D., Jonsson H., Redemann J., Eilers J., Ricci K., Hallar A., Clayton M., Michalsky J., Smirnov A., Holben B. & Barnard J. (2006). How well do state-of-the-art techniques measuring the vertical profile of tropospheric aerosol extinction compare?. Vol. 111. Journal of Geophysical Research Atmospheres. Published, 03/16/2006.
  • Hallar A., Avallone L., Herman R., Anderson B. & Heymsfield A. (2004). Measurements of ice water content in tropopause region Arctic cirrus during the SAGE III Ozone Loss and Validation Experiment (SOLVE). Vol. 109. Journal of Geophysical Research D: Atmospheres. Published, 09/16/2004.