edu.ucar.opensky::articles:12465 UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact 2025-12-26T03:48:34.012755 ISO 19115-2 Geographic Information - Metadata - Part 2: Extensions for Imagery and Gridded Data ISO 19115-2:2009(E) https://n2t.org/ark:/85065/d751400j Evaluation of HOx sources and cycling using measurement-constrained model calculations in a 2-methyl-3-butene-2-ol (MBO) and monoterpene (MT) dominated ecosystem 2013-02-21T00:00:00Z publication https://n2t.org/ark:/85065/d751400j https://doi.org/10.5194/acp-13-2031-2013 Kim, Saewung author Wolfe, G. author Mauldin, Roy author Cantrell, Chris A. author Guenther, Alex B. author Karl, Thomas author Turnipseed, Andrew A. author Greenberg, James author Hall, Samuel R. author Ullmann, Kirk author Apel, Eric C. author Hornbrook, Rebecca author Kajii, Y. author Nakashima, Y. author Keutsch, F. author DiGangi, J. author Henry, S. author Kaser, L. author Schnitzhofer, R. author Graus, M. author Hansel, A. author Zheng, Wengang author Flocke, Frank M. author UCAR/NCAR - Library publisher We present a detailed analysis of OH observations from the BEACHON (Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H₂O, Organics and Nitrogen)-ROCS (Rocky Mountain Organic Carbon Study) 2010 field campaign at the Manitou Forest Observatory (MFO), which is a 2-methyl-3-butene-2-ol (MBO) and monoterpene (MT) dominated forest environment. A comprehensive suite of measurements was used to constrain primary production of OH via ozone photolysis, OH recycling from HO2, and OH chemical loss rates, in order to estimate the steady-state concentration of OH. In addition, the University of Washington Chemical Model (UWCM) was used to evaluate the performance of a near-explicit chemical mechanism. The diurnal cycle in OH from the steady-state calculations is in good agreement with measurement. A comparison between the photolytic production rates and the recycling rates from the HO₂ + NO reaction shows that recycling rates are ~20 times faster than the photolytic OH production rates from ozone. Thus, we find that direct measurement of the recycling rates and the OH loss rates can provide accurate predictions of OH concentrations. More importantly, we also conclude that a conventional OH recycling pathway (HO₂ + NO) can explain the observed OH levels in this non-isoprene environment. This is in contrast to observations in isoprene-dominated regions, where investigators have observed significant underestimation of OH and have speculated that unknown sources of OH are responsible. The highly-constrained UWCM calculation under-predicts observed HO2 by as much as a factor of 8. As HO₂ maintains oxidation capacity by recycling to OH, UWCM underestimates observed OH by as much as a factor of 4. When the UWCM calculation is constrained by measured HO₂, model calculated OH is in better agreement with the observed OH levels. Conversely, constraining the model to observed OH only slightly reduces the model-measurement HO₂ discrepancy, implying unknown HO₂ sources. These findings demonstrate the importance of constraining the inputs to, and recycling within, the ROx radical pool (OH + HO₂ + RO₂). UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact PDF Text theme Resource Type 2016-01-01T00:00:00Z publication Copyright Author(s) 2013. This work is distributed under the Creative Commons Attribution 3.0 License None eng geoscientificInformation