Airborne Flux Measurements of BVOCs above Californian Oak Forests: Experimental Investigation of Surface and Entrainment Fluxes, OH Densities, and Damköhler Numbers
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Authors
Karl, T.
Misztal, P.K.
Jonnson, H.H.
Shertz, S.
Goldstein, A.H.
Guenther, A.B.
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2013-10
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Abstract
Airborne flux measurements of isoprene were performed over the Californian oak belts surrounding the
Central Valley. The authors demonstrate for the first time 1) the feasibility of airborne eddy covariance
measurements of reactive biogenic volatile organic compounds; 2) the effect of chemistry on the vertical
transport of reactive species, such as isoprene; and 3) the applicability of wavelet analysis to estimate regional
fluxes of biogenic volatile organic compounds. These flux measurements demonstrate that instrumentation
operating at slower response times (e.g., 1–5 s) can still be used to determine eddy covariance fluxes in the
mixed layer above land, where typical length scales of 0.5–3km were observed. Flux divergence of isoprene
measured in the planetary boundary layer (PBL) is indicative of OH densities in the range of 4–7 3 106
molecules per cubic centimeter and allows extrapolation of airborne fluxes to the surface with Damk€ohler
numbers (ratio between the mixing time scale and the chemical time scale) in the range of 0.3–0.9. Most of the
isoprene is oxidized in the PBL with entrainment fluxes of about 10% compared to the corresponding surface
fluxes. Entrainment velocities of 1–10 cm s21 were measured. The authors present implications for parameterizing
PBL schemes of reactive species in regional and global models.
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Article
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The article of record as published may be located at http://dx.doi.org/10.1175/JAS-D-13-054.1
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Meteorology
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Journal of the Atmospheric Sciences, Vol. 70, pp. 3277-3287, October 2013
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This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.