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Featured researches published by R. F. Hansen.


Journal of Geophysical Research | 2016

Measurements of hydroxyl and hydroperoxy radicals during CalNex‐LA: Model comparisons and radical budgets

Stephen M. Griffith; R. F. Hansen; S. Dusanter; Vincent Michoud; J. B. Gilman; William C. Kuster; P. R. Veres; Martin Graus; J. A. de Gouw; James M. Roberts; Cora J. Young; Rebecca A. Washenfelder; Steven S. Brown; Ryan Thalman; Eleanor M. Waxman; R. Volkamer; Catalina Tsai; J. Stutz; James Flynn; N. Grossberg; Barry Lefer; S. Alvarez; Bernhard Rappenglueck; Levi H Mielke; Hans D. Osthoff; Philip S. Stevens

Measurements of hydroxyl (OH) and hydroperoxy (HO2*) radical concentrations were made at the Pasadena ground site during the CalNex-LA 2010 campaign using the laser-induced fluorescence-fluorescence assay by gas expansion technique. The measured concentrations of OH and HO2* exhibited a distinct weekend effect, with higher radical concentrations observed on the weekends corresponding to lower levels of nitrogen oxides (NOx). The radical measurements were compared to results from a zero-dimensional model using the Regional Atmospheric Chemical Mechanism-2 constrained by NOx and other measured trace gases. The chemical model overpredicted measured OH concentrations during the weekends by a factor of approximately 1.4 ± 0.3 (1σ), but the agreement was better during the weekdays (ratio of 1.0 ± 0.2). Model predicted HO2* concentrations underpredicted by a factor of 1.3 ± 0.2 on the weekends, while measured weekday concentrations were underpredicted by a factor of 3.0 ± 0.5. However, increasing the modeled OH reactivity to match the measured total OH reactivity improved the overall agreement for both OH and HO2* on all days. A radical budget analysis suggests that photolysis of carbonyls and formaldehyde together accounted for approximately 40% of radical initiation with photolysis of nitrous acid accounting for 30% at the measurement height and ozone photolysis contributing less than 20%. An analysis of the ozone production sensitivity reveals that during the week, ozone production was limited by volatile organic compounds throughout the day during the campaign but NOx limited during the afternoon on the weekends.


Atmospheric Chemistry and Physics | 2012

In-canopy gas-phase chemistry during CABINEX 2009: Sensitivity of a 1-D canopy model to vertical mixing and isoprene chemistry

A. M. Bryan; Steven B. Bertman; Mary Anne Carroll; S. Dusanter; G. D. Edwards; Renate Forkel; Stephen M. Griffith; Alex Guenther; R. F. Hansen; Detlev Helmig; B. T. Jobson; Frank N. Keutsch; Barry Lefer; Shelley Pressley; Paul B. Shepson; Philip S. Stevens; Allison L. Steiner


Atmospheric Chemistry and Physics | 2012

OH and HO 2 radical chemistry during PROPHET 2008 and CABINEX 2009 – Part 1: Measurements and model comparison

Stephen M. Griffith; R. F. Hansen; S. Dusanter; Philip S. Stevens; M. Alaghmand; S. B. Bertman; Mary Anne Carroll; M. Erickson; M. M. Galloway; N. Grossberg; John Robert Hottle; J. Hou; B. T. Jobson; Aster E Kammrath; Frank N. Keutsch; Barry Lefer; Levi H Mielke; A. O'Brien; Paul B. Shepson; M. Thurlow; W. Wallace; N. Zhang; X. Zhou


Atmospheric Chemistry and Physics | 2013

Measurements of total hydroxyl radical reactivity during CABINEX 2009 – Part 1: field measurements

R. F. Hansen; Stephen M. Griffith; S. Dusanter; P. S. Rickly; Philip S. Stevens; S. B. Bertman; Mary Anne Carroll; M. H. Erickson; James Flynn; N. Grossberg; B. T. Jobson; Barry Lefer; H. W. Wallace


Atmospheric Measurement Techniques | 2015

Detailed characterizations of the new Mines Douai comparative reactivity method instrument via laboratory experiments and modeling

Vincent Michoud; R. F. Hansen; Nadine Locoge; Philip S. Stevens; S. Dusanter


Atmospheric Environment | 2012

Observations and modeling of formaldehyde at the PROPHET mixed hardwood forest site in 2008

M. M. Galloway; Joshua Digangi; John Robert Hottle; Andrew J. Huisman; Levi H Mielke; M. Alaghmand; Paul B. Shepson; Joanna Weremijewicz; Hugh Klavon; Fredrick M. McNeal; Mary Anne Carroll; Stephen M. Griffith; R. F. Hansen; S. Dusanter; Philip S. Stevens; Steven B. Bertman; Frank N. Keutsch


Atmospheric Chemistry and Physics | 2016

Differences in BVOC oxidation and SOA formation above and below the forest canopy

Benjamin C. Schulze; H. W. Wallace; James Flynn; Barry Lefer; M. H. Erickson; B. Tom Jobson; S. Dusanter; Stephen M. Griffith; R. F. Hansen; Philip S. Stevens; Timothy M. VanReken; Robert J. Griffin


Archive | 2009

Measurements of Product-Specific VOC Reactivities during the PROPHET 2008 field intensive using proton transfer reaction linear ion trap (PTR-LIT) mass spectrometry

Levi H Mielke; Jonathan H. Slade; M. Alaghmand; Stephen Bertman; Mary Anne Carroll; Steve Griffith; R. F. Hansen; S. Dusanter; Paul Stevens; Armin Hansel; Paul B. Shepson


Journal of Geophysical Research | 2016

Measurements of hydroxyl and hydroperoxy radicals during CalNex-LA: Model comparisons and radical budgets: HOxRadicals During CalNex-LA

Stephen M. Griffith; R. F. Hansen; S. Dusanter; Vincent Michoud; J. B. Gilman; William C. Kuster; P. R. Veres; Martin Graus; J. A. de Gouw; James M. Roberts; Cora J. Young; Rebecca A. Washenfelder; Steven S. Brown; Ryan Thalman; Eleanor M. Waxman; R. Volkamer; Catalina Tsai; J. Stutz; James Flynn; N. Grossberg; Barry Lefer; S. Alvarez; Bernhard Rappenglueck; Levi H Mielke; Hans D. Osthoff; Philip S. Stevens


Atmospheric Measurement Techniques Discussions | 2015

Detailed characterizations of a Comparative Reactivity Method (CRM) instrument: experiments vs. modelling

Vincent Michoud; R. F. Hansen; Nadine Locoge; Philip S. Stevens; S. Dusanter

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M. M. Galloway

University of Wisconsin-Madison

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Philip S. Stevens

Indiana University Bloomington

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Aster E Kammrath

University of Wisconsin-Madison

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