A Lagrangian dispersion model for predicting CO{sub 2} sources, sinks, and fluxes in a uniform loblolly pine ({ital Pinus taeda L.}) stand
- School of the Environment, Duke University, Durham, North Carolina (United States)
- Department of Applied Sciences, Brookhaven National Laboratory, Upton, New York (United States)
A canopy Lagrangian turbulent scalar transport model for predicting scalar fluxes, sources, and sinks within a forested canopy was tested using CO{sub 2} concentration and flux measurements. The model formulation is based on the localized near-field theory (LNF) proposed by {ital Raupach} [1989a, b]. Using the measured mean CO{sub 2} concentration profile, the vertical velocity variance profile, and the Lagrangian integral timescale profile within and above a forested canopy, the proposed model predicted the CO{sub 2} flux and source (or sink) profiles. The model testing was carried out using eddy correlation measurements at 9 m in a uniform 13 m tall {ital Pinus taeda L.} (loblolly pine) stand at the Blackwood division of the Duke Forest near Durham, North Carolina. The tree height and spacing are relatively uniform throughout. The measured vertical profile leaf area index (LAI) was characterized by three peaks, with a maximum LAI occurring at 6.5 m, in qualitative agreement with the LNF source-sink predicted profile. The LNF CO{sub 2} flux predictions were in better agreement with eddy correlation measurements (coefficient of determination r{sup 2}=0.58; and standard error of estimate equal to 0.16mgkg{sup {minus}1}ms{sup {minus}1}) than K theory. The model reproduced the mean diurnal CO{sub 2} flux, suggesting better performance over longer averaging time periods. Two key simplifications to the LNF formulation were considered, namely, the near-Gaussian approximation to the vertical velocity and the absence of longitudinal advection. It was found that both of these assumptions were violated throughout the day, but the resulting CO{sub 2} flux error at 9 m was not strongly related to these approximations. In contrast to the forward LNF approach utilized by other studies, this investigation demonstrated that the inverse LNF approach is sensitive to near-field corrections.{copyright} 1997 American Geophysical Union
- OSTI ID:
- 526885
- Journal Information:
- Journal of Geophysical Research, Vol. 102, Issue D8; Other Information: PBD: Apr 1997
- Country of Publication:
- United States
- Language:
- English
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