HR: 0800h
AN: B41B-0199    [Abstracts]
TI: Estimating Mean Boundary Layer Turnover from Radon Concentration to Retrieve Surface Fluxes of CO2
AU: * Wolf, A
EM: adamwolf@stanford.edu
AF: Carnegie Institution of Washington, Department of Global Ecology 260 Panama St., Stanford, CA 94305 United States
AU: Berry, J A
EM: joeberry@stanford.edu
AF: Carnegie Institution of Washington, Department of Global Ecology 260 Panama St., Stanford, CA 94305 United States
AU: Helliker, B
B41B-0199 AF: University of Pennsylvania, Department of Biology 415 S University Avenue, Philadelphia, PA 19104
AB: Chemical transport models have been widely used in inversion studies to infer sources and sinks of carbon dioxide from CO₂ concentration measurements at remote marine boundary layer sites. In this study, we evaluate an alternative method of inferring sources and sinks of CO₂ from land-based concentration measurements using the equilibrium boundary layer (EBL) method (Helliker et al., JGR 109:D20106). This gives estimates regional-scale fluxes of carbon dioxide between the planetary boundary layer (PBL) and free troposphere (FT) using mean concentration measurements of CO₂ and an estimate of the mean vertical wind vector. Although the EBL method has been successfully applied at a tall tower site in Wisconsin, there are a number of practical and theoretical impediments to its operational use. First, there are few long-term measurements of CO₂ in the troposphere. Second, the mean vertical wind velocity is a very small value (~0.01 m/s) and difficult to observe relative to the dramatic growth of the daytime boundary layer. In this study we use an atmospheric tracer transport model to simulate the FT CO₂ concentration and to calculate the effective turnover time of the boundary layer air mass. We then evaluate the ability of the EBL method to retrieve surface fluxes of CO₂ from land concentration data and modeled vertical winds. Atmospheric concentrations of CO₂ and 222-Rn were simulated using the Paramaterized Chemical Transport Model (PCTM). PCTM uses the GEOS-4 assimilated wind fields of the NASA Global Modeling and Assimulation Office. We inferred the effective conductance between the PBL and FT using the concentration difference across the PBL-FT boundary, assuming a constant, known land surface radon flux (1 atom cm^-2 s^-1). This vertical velocity is then used to calculate the PBL-FT flux of CO₂. We also evaluate the use of PBL climatology estimated from PCTM to reconstruct surface fluxes in conjunction with CO₂ measurements at the WLEF tall tower in Wisconsin. This is shown as a step toward using statistics derived from transport models in conjunction with a CO₂ monitoring network to continously monitor CO₂ fluxes at a continental scale.
DE: 0368 Troposphere: constituent transport and chemistry
DE: 0428 Carbon cycling (4806)
DE: 0438 Diel, seasonal, and annual cycles (4227)
SC: Biogeosciences [B]
MN: Fall Meeting 2005