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Professional Interests

The overarching theme of my 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 my research uses high elevation sites, combined with airborne measurements, to study the formation processes of Cloud Condensation Nuclei (CCN) and Ice Nuclei (IN) and how differing formation processes impact mixed-phase cloud microphysics. This research topic is stemmed in many potential formation mechanisms of aerosols, including nucleation, secondary organic aerosols, and primary biological aerosol particles (PBAP's).

In addition to my research, I guided two large National Science Foundation programs to support diversity in the atmospheric sciences. Geoscience Research at Storm Peak (GRASP) is a program providing mentoring and field research experiences for a diverse group of undergraduate students. Atmospheric Science Collaborations and Enriching NeTworks (ASCENT) is a program focusing on women in atmospheric science/meteorology to initiate positive professional relationships among female faculty of different ranks and postdoctoral researchers. Finally, I am interested in science administration and have served as the Program Director of Physical and Dynamic Meteorology within the Division of Atmospheric and Geospace Sciences at the National Science Foundation.

Research Areas

• Cloud Microphysics
• In Situ Trace Gas Measurements
• Aerosol Optical Properties

Education

Degree	Institution	Field
Ph.D.	University of Colorado at Boulder	Atmospheric and Oceanic Sciences
M.S.	University of Colorado at Boulder	Atmospheric and Oceanic Sciences
B.S.	Truman State University	Physics

Publications

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. Discuss., https://doi.org/10.5194/acp-2018-822, 2018. link

 

Collaud Coen, M., Andrews, E., Aliaga, D., Andrade, M., Angelov, H., Bukowiecki, N., Ealo, M., Fialho, P., Flentje, H., Hallar, A. G., Hooda, R., Kalapov, I., Krejci, R., Lin, N.-H., Marinoni, A., Ming, J., Nguyen, N. A., Pandolfi, M., Pont, V., Ries, L., Rodríguez, S., Schauer, G., Sellegri, K., Sharma, S., Sun, J., Tunved, P., Velasquez, P., and Ruffieux, D.: Identification of topographic features influencing aerosol observations at high altitude stations, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-18-12289-2018, 2018. link

 

Hallar, A.G., N. Molotch, J. Hand, B. Livneh, I. McCubbin, R. Petersen, J. Michalsky, and D. Lowenthal (2017), Impacts of Increasing Aridity and Wildfires on Aerosol Loading in the Intermountain Western U.S., Environ. Res. Lett., 12(1) link

 

Taylor, N., D. Collins, D. Lowenthal, B. Zielinska, V. Samburova, N. Kumar, G. Hallar, L. Mazzoleni, and I. McCubbin (2016), Hygroscopic growth of water soluble organic carbon isolated from atmospheric aerosol collected at U.S. national parks and Storm Peak Laboratory, Atmospheric Chemistry and Physics., 17, 2555-2571, doi:10.5194/acp-17-2555-2017 link

 

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 (2016), 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 doi:10.1175/JAS-D-16-0256.1 link

 

Sullivan, R. C., Crippa, P., Hallar A. G., Clarisse, L., Leaitch, W. R., Aneja, V. P., and Pryor S.C. (2016), Using satellite-based measurements to explore spatiotemporal scales and variability of drivers of new particle formation, J. of Geophysical Research, 121(20), doi:10.1002/2016JD025568 link

 

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, 16(3), 471-477, doi:10.4209/aaqr.2016.02.0077 link

 

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), 2663-2678. doi:10.1175/JTECH-D-15-0233.1 link

 

Yu, F., G. Luo, A. G. Hallar (2016), Vertical profiles and seasonal variations of key parameters controlling particle formation and growth at Storm Peak Laboratory, Aerosol and Air Quality Research, 16(3), 900-908, doi:10.4209/aaqr.2015.05.0341 link

 

Hallar, A.G. R. Petersen, I. B. McCubbin, D. Lowenthal, S. Lee, E. Andrews, F. Yu (2016), Climatology of New Particle Formation and Corresponding Precursors at Storm Peak Laboratory, Aerosol and Air Quality Research, 16(3), 816-826, doi:10.4209/aaqr.2015.05.0341, link

 

Hallar, A.G., R. Petersen, E. Andrews, J. Michalsky, I. B. McCubbin, J. A. Ogren (2015), Contributions of Dust and Biomass burning to Aerosols at a Colorado Mountain-top Site, Atmos. Chem. Phys., 15, 13665-13679, doi:10.5194/acp-15-13665-2015 link

 

Yu, F., G. Luo, S. C. Pryor, P. R. Pillai, S. H. Lee, J. Ortega, J. J. Schwab, A. G. Hallar, W. R. Leaitch, V. P. Aneja, J. N. Smith, J. T. Walker, O. Hogrefe, and K. L. Demerjian (2015), Spring and summer contrast in new particle formation over nine forest areas in North America, Atmos. Chem. Phys., 15,13993-14003, doi:10.5194/acp-15-13993-2015 link

 

Goliff, W., M. Luria, D. R. Blake, B. Zielinska, A.G. Hallar, R. J. Valente, C. V. Lawson, W.R. Stockwell (2015), Nighttime air quality under desert conditions, Atmospheric Environment, 114,102-111, doi:10.1016/j.atmosenv.2015.05.041 link

 

Kristensen, T.B., L. Du, Q. T. Nguyen, J. K. Nojgaard, C. Bender Koch, O. Faurskov Nielsen, A. G. Hallar, D. H. Lowenthal, B. Nekat, D. van Pinxteren, H. Herrmann, M. Glasius, H. G. Kjaergaard, M. Bilde (2015), Chemical Properties of HULIS from Different Environments, Journal of Atmospheric Chemistry, 72 (1), 65-80, doi:10.1007/s10874-015-9302-8 link

 

Yu, F. and A. G. Hallar (2014), Difference in particle formation at a mountaintop location during spring and summer: Implications for the role of sulfuric acid and organics in nucleation, J. of Geophysical Research, 119(21), doi:10.1002/2014JD022136 link

 

Yu, H., A. G. Hallar, Y. You, A. Sedlacek, S. Springston, V. P. Kanawade, Y. N. Lee, J. Wang, C. Kuang, R. L. McGraw, I.B. McCubbin, J. Mikkila and S. H. Lee (2013), Sub-3 nm Particles Observed at the Coastal and Continental Sites in the United States, J. of Geophysical Research, 119, doi:10.1002/2013JD020841. link

 

Hallar, A.G., D. H. Lowenthal, S. L. Clegg, V. Samburova, N. Taylor, L. R Mazzoleni, B. K. Zielinska, T. B Kristensen, G. Chirokova, I. B. McCubbin, C. Dodson, D. Collins (2013), Chemical and Hygroscopic Properties of Aerosol Organics at Storm Peak Laboratory, J. of Geophysical Research, 118, 4767-4779, doi:10.1002/jgrd.50373. link

 

Zhao, Y., A. G. Hallar, and L. R. Mazzoleni (2013), Atmospheric organic matter in clouds: exact masses and molecular formula identification using ultrahigh- resolution FT-ICR mass spectrometry, Atmos. Chem. Phys., 13, 12343-12362, doi:10.5194/acp-13-12343-2013 link

 

Friedman, B., A. Zelenyuk, J. Beránek, G. Kulkarni, M. Pekour, A.G. Hallar, I.B. McCubbin, J. A. Thornton, and D. J. Cziczo (2013), Aerosol measurements at a high-elevation site: composition, size, and cloud condensation nuclei activity, Atmos. Chem. Phys., 13, 11839-11851, doi:10.5194/acp-13-11839-2013 link

 

Asmi, A., M. Collaud Coen,, J.A. Ogren, E. Andrews, P. Sheridan, A. Jefferson, E. Weingartner, U. Baltensperger, N. Bukowiecki, H. Lihavainen, N. Kivekäs, E. Asmi, P. P. Aalto, M. Kulmala,, A. Wiedensohler, W. Birmili, A. Hamed, C. O'Dowd, S.G. Jennings, R. Weller, H. Flentje, A.M. Fjaeraa, M. Fiebig, C.L. Myhre, A. G. Hallar, E. Swietlicki, A. Kristensson, and P. Laj (2013), Aerosol decadal trends – Part 2: In-situ aerosol particle number concentrations at GAW and ACTRIS stations, Atmos. Chem. Phys., 13, 895-916, doi:10.5194/acp-13-895-2013 lnik

 

Amin, H. S, R. S. Russo, B. Sive, E. R. Hoebeke, C. Dodson, I. B. McCubbin, A. G. Hallar, K. E. Huff Hartz (2013), Monoterpene emissions from bark beetle infested Engelmann spruce trees, Atmospheric Environment, 72, 130-133, doi:10.1016/j.atmosenv.2013.02.025 link

 

Berg, A. R., C.L. Heald, K. E. Huff Hartz, A.G. Hallar, A. J. H. Meddens, J.A. Hicke, J.-F. Lamarque, and S. Tilmes (2013), The impact of bark beetle infestations on monoterpene emissions and secondary organic aerosol formation in western North America, Atmos. Chem. Phys., 13, 3149-3161, doi:10.5194/acp-13-3149-2013 link

 

Samburova, V., A. G. Hallar, L. R. Mazzoleni, P. Saranjampour, D. Lowenthal, S. Kohl, and B. Zielinska (2013), Composition of the water-soluble organic carbon in non-urban atmospheric aerosol collected at Storm Peak Laboratory, Environmental Chemistry, 10(5), 370-380, doi:10.1071/EN1309 link

 

Marchand, R., G. G. Mace, A. G. Hallar, I. B. McCubbin, S. Y. Matrosov and M. Shupe (2013), Enhanced Radar Backscattering due to Oriented Ice Particles at 95 GHz during StormVEx, J. of Atmospheric and Oceanic Technology, doi:10.1175/JTECH-D-13-00005.1 lnik

 

Hallar, A.G., L. Avallone, H. Thiry, and L. Edwards (2015), ASCENT, A Discipline Specific Model to Support the Retention and Advancement of Women in Science, American Geophysical Union Book Series, Best Practices towards Gender Parity in the Academic Science Departments, 70, 135. link

 

Avallone, L, A. G. Hallar, H. Thiry, L. M. Edwards (2013), Supporting the Retention and Advancement of Women in the Atmospheric Sciences: What women are saying" Bulletin of the American Meteorological Society, 94, 1313–1316, doi:10.1175/BAMS-D-12-00078.1 link

 

Hallar, A.G., A. Fridlind, J. A. Huffman (2012), Biological Aerosol Effects on Clouds and Precipitation, EOS, Meeting Summary, 93, 51, December 18.

 

Kristensen, T., H. Wex, B. Nekat, J. K. Nųjgaard, D. van Pinxteren, D. H. Lowenthal, L. R. Mazzoleni, K. Dieckmann, C.B. Koch, T. F. Mentel, H. Herrmann, A. G. Hallar, F. Stratmann, and Merete Bilde (2012), Hygroscopic growth and CCN activity of HULIS from different environments, J. of Geophysical Research, 117(D22), 27, doi:10.1029/2012JD018249 link

 

Mazzoleni, L.R., P. Saranjampour, M. M. Dalbec, V. Samburova, A. G. Hallar, B. Zielinska, D. Lowenthal, and Steve Kohl (2012), Identification of water-soluble organic carbon in non-urban aerosols using ultrahigh-resolution FT-ICR mass spectrometry: organic anions, Environmental Chemistry, 9(3) doi:10.1071/EN11167 link

 

Amin, H., P.T. Atkins, R. Russo, A. W. Brown, B. Sive, A. G. Hallar, K.E. Huff Hartz (2012), Effect of Bark Beetle Infestation on Secondary Organic Aerosol Precursor Emissions, Environmental Science and Technology, 46(11), 5696–5703, doi:10.1021/es204205m link

 

Matrosov, S.Y., G. G. Mace, R. Marchand, M. D. Shupe, A. G. Hallar, I. B. McCubbin, 2012: Influence of Ice Hydrometeor Habits on Scanning Polarimertic Cloud Radar Measurements, J. of Atmospheric and Oceanic Technology, 29, 989-1008.

 

Baustian, K. J., D. J. Cziczo, M. E. Wise, K. A. Pratt, G. Kulkarni, A. G. Hallar, and M. A. Tolbert (2012), Importance of aerosol composition, mixing state, and morphology for heterogeneous ice nucleation: A combined field and laboratory approach, J. of Geophysical Research, 117(D6), D06217, doi:10.1029/2011JD016784 link

 

Bowers, R.M., I. B. McCubbin, A.G. Hallar, N. Fierer (2012), Seasonal variability in airborne bacterial communities at a high-elevation site, Atmospheric Environment, 50, 41–49, doi: 10.1016/j.atmosenv.2012.01.005 link

 

Hallar, A.G., G. Chirokova, I.B. McCubbin, T.H. Painter, C. Wiedinmyer, C. Dodson (2011), Atmospheric Bioaerosols Transported Via Dust Storms in the Western United States, Geophysical Res. Letters, an AGU Journal, 38(17), doi:10.1029/2011GL048166 link

 

Hallar, A.G., I. B. McCubbin, J. M. Wright (2011), CHANGE: A Place-Based Curriculum for Understanding Climate Change at Storm Peak Laboratory, Colorado, Bulletin of the American Meteorological Society, doi: 10.1175/2011BAMS3026.1 link

 

Hallar, A.G., D. H. Lowenthal, G. Chirokova. C. Wiedinmyer, R.D. Borys (2011), Persistent Daily New Particle Formation at a Mountain-Top Location, Atmospheric Environment, 45(24), 4111-4115 doi:10.1016/j.atmosenv.2011.04.044 link

 

Hoyle, C.R., M. Boy, N.M. Donahue, J.L. Fry, M. Glasius, A. Guenther, A.G. Hallar, K. Huff Hartz, M.D. Petters, T. Petäjä, T. Rosenoern, and A.P. Sullivan, 2010: Anthropogenic influence on biogenic secondary organic aerosol, Atmos. Chem. Phys., 10, 19515-19566, doi:10.5194/acpd-10-19515-2010 link

 

Strawa, A.W., T.W. Kirchstetter, A.G. Hallar, G.A. Ban-Weiss, J.P. McLaughlin, R.A. Harley, and M.M. Lunden (2010), Optical and physical properties of primary on-road vehicle particle emissions and their implications for climate change, J. of Aerosol Science, 41(1), 36-50. link

 

Hallar, A.G., I.B. McCubbin, B. Hallar, R. Levine, W. Stockwell, J. Lopez, J. Wright (2010), Science in the Mountains: A Unique Research Experience to Enhance Diversity in the Geosciences, J. GeoScience Education, 58(2), 213-220. link

 

Samy, S., L.R. Mazzoleni, S. Mishra, B. Zielinska, and A.G. Hallar (2010), Water-soluble organic compounds at a mountain-top Site in Colorado, USA, Atmos. Environ., 44(13), 1663-1671. lnk

 

de Wekker, S.F.J., A. Ameen, G. Song, B.B. Stephens, A.G. Hallar, and I.B. McCubbin (2009), A preliminary investigation of boundary layer effects on daytime atmospheric CO2 concentrations at a mountaintop location in the Rocky Mountains, Acta Geophysica, 57(4), 904-922 doi:10.2478/s11600-009-0033-6 link

 

Wiedinmyer, C., R.M. Bowers, N. Fierer, E. Horanyi, M. Hannigan, A.G. Hallar, I. McCubbin, K. Baustian (2009), The contribution of biological particles to observed particulate organic carbon at a remote high altitude site. Atmos. Environ., 43(28), 4278–4282, doi:10.1016/j.atmosenv.2009.06.012 link

 

Faĩn, X., D. Obrist, A. G. Hallar, I. McCubbin, and T. Rahn (2009), High levels of reactive gaseous mercury observed at a high elevation research laboratory in the Rocky Mountains, Atmos. Chem. Phys., 9, 8049-8060. link

 

Bowers, R.M., C.L. Lauber, C. Wiedinmyer, M. Hamady, A.G. Hallar, R. Fall, R. Knight, and N. Fierer (2009), Characterization of Airborne Microbial Communities at a High-Elevation Site and their Potential to Act as Atmospheric Ice Nuclei, Applied and Environmental Microbiology, 75(15), 1–2, doi:10.1128/AEM.00447-09 link

 

Obrist D., A.G. Hallar, I. McCubbin, B.B. Stephens, and T. Rahn (2008), Measurements of atmospheric mercury at Storm Peak Laboratory in the Rocky Mountains: Evidence for local/ regional emissions and influence of long-range transport from Asia, boundary layer contributions, and plant mercury uptake. Atmos. Environ., doi:10.1016/j.atmosenv.2008.06.051 link

 

Davis, S., A. G. Hallar, L. M. Avallone, T. Campos, B. Engblom (2006), Measurement of total water with a tunable diode laser hygrometer: Inlet analysis calibration procedure, and ice water content determination, J. Atmos. and Oceanic Technol., 24(3), 463–475, doi:10.1175/JTECH1975.1 link

 

Hallar, A.G., A.W. Strawa, B. Schmid, E. Andrews, J. Ogren, P. Sheridan, R. Ferrare, D. Covert, R. Elleman, H. Jonsson, K. Bokarius, A. Luu (2006), Atmospheric Radiation Measurements Aerosol Intensive Operating Period: Comparison of aerosol scattering during coordinated flights, J. of Geophysical Research, 111(D5), doi:2005JD006250RR link

 

Thornton, B.F., D.W. Toohey, L.M. Avallone, A. G. Hallar, H. Harder, M. Martinez, J. B. Simpas, W. H. Brune, M. Koike, Y. Kondo, N. Takegawa, B. E. Anderson, M. A. Avery (2005), Variability of active chlorine in the lowermost Arctic stratosphere, J. of Geophysical Research, 110(D22), doi:10.1029/2004JD005580 link

 

Strawa, A.W., R. Elleman, A.G. Hallar, D. Covert, K. Ricci, R. Provencal, T. Owano, H. Jonsson, B. Schmid, A. Luu, K. Bokarius, E. Andrews (2005), Comparison of in situ aerosol extinction and scattering coefficient measurements made during the Aerosol Intensive Operating Period, J. of Geophysical Research, 111(D5), doi:10.1029/2005JD006056 link

 

Schmid, B., R. Ferrare, C. Flynn, R. Elleman, D. Covert, A. Strawa, E. Welton, D. Turner, H. Jonsson, J. Redemann, J. Eilers, K. Ricci, A. G. Hallar, M. Clayton, J. Michalsky, A. Smirnov, B. Holben, J. Barnard (2005) How well do state-of-the-art techniques measuring the vertical profile of tropospheric aerosol extinction compare? J. of Geophysical Research, 111(D5), doi:10.1029/2005JD005837 link

 

Lopez, J., A. Fridlind, H-J Jost, M. Loewenstein, A. Ackerman, T. Campos, E. Weinstock, D. Sayres, J.B. Smith, J. Pittman, A. G. Hallar, L. Avallone, S. Davis, R. Herman (2005), 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, J. of Geophysical Research, 111(D9), doi:10.1029/2005JD006104 link

 

Hallar, A.G., L.M. Avallone, R.L. Herman, B.E. Anderson, and A.J. Heymsfield, 2004: Measurements of ice water content in tropopause region Arctic cirrus during the SAGE III Ozone Loss and Validation Experiment (SOLVE). J. of Geophysical Research, 109(D17), doi:10.1029/2003JD004348 link

 

Kondo, Y., O.B. Toon, H. Irie, B. Gamblin, M. Koike, N. Takegawa, M.A. Tolbert, P.K. Hudson, A.A. Viggiano, L.M. Avallone, A.G. Hallar, B.E. Anderson, G.W. Sachse, D.E. Hunton, J.O. Balentine, and T.M. Miller (2003), Uptake of reactive nitrogen on cirrus cloud particles in the upper troposhpere and lowermost stratosphere. Geophysical Research Letters, 30(4), 1154, doi:10.1029/2002GL016539 link