edu.ucar.opensky::articles:18500 UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact 2025-12-26T02:48:20.861335 ISO 19115-2 Geographic Information - Metadata - Part 2: Extensions for Imagery and Gridded Data ISO 19115-2:2009(E) https://n2t.org/ark:/85065/d7hq41j4 Understanding isoprene photooxidation using observations and modeling over a subtropical forest in the southeastern US 2016-06-24T00:00:00Z publication https://n2t.org/ark:/85065/d7hq41j4 https://doi.org/10.5194/acp-16-7725-2016 Su, L. author Patton, Edward G. author Vila-Guerau de Arrelano, J. author Guenther, A. author Kaser, Lisa author Yuan, B. author Xiong, F. author Shepson, P. author Zhang, L. author Miller, D. author Brune, W. author Baumann, K. author Edgerton, E. author Weinheimer, Andrew author Misztal, P. author Park, J. author Goldstein, A. author Skog, K. author Keutsch, F. author Mak, J. author UCAR/NCAR - Library publisher The emission, dispersion, and photochemistry of isoprene (C5H8) and related chemical species in the convective boundary layer (CBL) during sunlit daytime were studied over a mixed forest in the southeastern United States by combining ground-based and aircraft observations. Fluxes of isoprene and monoterpenes were quantified at the top of the forest canopy using a high-resolution proton transfer reaction time-of-flight mass spectrometer (PTR-TOF-MS). Snapshot (∼20min sampling duration) vertical profiles of isoprene, methyl vinyl ketone (MVK)+methacrolein (MACR), and monoterpenes were collected from aircraft every hour in the CBL (100-1000m). Both ground-based and airborne collected volatile organic compound (VOC) data are used to constrain the initial conditions of a mixed-layer chemistry model (MXLCH), which is applied to examine the chemical evolution of the O3-NOx-HOx-VOC system and how it is affected by boundary layer dynamics in the CBL. The chemical loss rate of isoprene (∼10h) is similar to the turbulent mixing timescale (0.1-0.50h), which indicates that isoprene concentrations are equally dependent on both photooxidation and boundary layer dynamics. Analysis of a model-derived concentration budget suggests that diurnal evolution of isoprene inside the CBL is mainly controlled by surface emissions and chemical loss; the diurnal evolution of O3 is dominated by entrainment. The NO to HO2 ratio (NO:HO2) is used as an indicator of anthropogenic impact on the CBL chemical composition and spans a wide range (1-163). The fate of hydroxyl-substituted isoprene peroxyl radical (HOC5H8OO·; ISOPOO) is strongly affected by NO:HO2, shifting from NO-dominant to NO-HO2-balanced conditions from early morning to noontime. This chemical regime change is reflected in the diurnal evolution of isoprene hydroxynitrates (ISOPN) and isoprene hydroxy hydroperoxides (ISOPOOH). 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) 2016. This work is distributed under the Creative Commons Attribution 3.0 License. None eng geoscientificInformation