Atmospheric Oxidation in a Southeastern US Forest: Examination of the Discrepancies Between Modeled and Observed OH in a Forest Environment

Philip Allen Feiner1, William H Brune2, Li Zhang3, David Owen Miller2, Paul O Wennberg4, Alex Teng5, Tran Nguyen6, John D Crounse5, Jason Michael St Clair5, Ronald C Cohen7, Kaitlin Duffey8, Paul Romer Present9, Allen H Goldstein10, Pawel K Misztal11, Kevin Frederick Olson12, Frank N Keutsch13, Kate Skog14, Joost A de Gouw15 and Abigail Koss16, (1)Pennsylvania State University Main Campus, University Park, PA, United States, (2)Pennsylvania State University, University Park, PA, United States, (3)Pennsylvania State Univ, University Park, PA, United States, (4)California Institute of Technology, Division of Geological and Planetary Sciences, Pasadena, United States, (5)California Institute of Technology, Pasadena, CA, United States, (6)California Institute of Technology, Pasadena, United States, (7)University of California, Berkeley, Department of Chemistry, Berkeley, United States, (8)UC Berkeley, Berkeley, CA, United States, (9)University of California Berkeley, Berkeley, CA, United States, (10)University of California Berkeley, Department of Civil & Environmental Engineering, Berkeley, CA, United States, (11)University of North Texas, Austin, United States, (12)University of California, Berkeley, CA, United States, (13)Harvard University, Cambridge, MA, United States, (14)Picarro, Inc., Santa Clara, CA, United States, (15)University of Colorado Boulder, Department of Chemistry, Boulder, United States, (16)University of Colorado at Boulder, Boulder, CO, United States
Abstract:
Significant oxidation chemistry occurs in the atmosphere in and above forests. In forests where levels of nitrogen oxides (NOx) are low, this chemistry is influenced primarily by the emissions and chemistry of highly reactive Biogenic Volatile Organic Compounds (BVOCs), which both destroy hydroxyl (OH, the main oxidant), and may produce it. Quantifying OH in forest environments is crucial to a proper understanding of the specific oxidation mechanisms taking place. In some other low-NOx / high-BVOC environments, OH measurements have been found to be several times higher than predicted by models, leading to concern that perhaps the current BVOC oxidation mechanisms are missing some OH-producing chemistry. The Southern Oxidant and Aerosol Study (SOAS) presents an excellent opportunity to closely examine these mechanisms as well as the recycling of OH thanks to its extensive suite of measurements taken in an Alabama forest during summer 2013. OH and HO2 measurements made with the Ground-based Tropospheric Hydrogen Oxides Sensor (GTHOS) are compared to the results of a photochemical box model constrained by the other measurements taken at SOAS. For this presentation, we examine the discrepancy between the measurements and the model output and discuss potential sources for this discrepancy.
Back to: Atmospheric Gas-Phase and Aerosol Chemistry over the Southeastern United States V Posters