Publications [#58540] of Gabriel Katul

Papers Published

1. Juang, J.Y. and Katul, G.G. and Siqueira, M.B.S. and Stoy, P.C. and Palmroth, S. and McCarthy, H.R. and Kim, H.-S. and Oren, R., Modeling nighttime ecosystem respiration from measured CO₂ concentration and air temperature profiles using inverse methods, J. Geophys. Res, D, Atmos. (USA), vol. 111 no. D8 (2006), pp. 16 pp. - [2005JD005976] .
   (last updated on 2007/04/09)

   Abstract:
   A major challenge for quantifying ecosystem carbon budgets from micrometeorological methods remains nighttime ecosystem respiration. An earlier study utilized a constrained source optimization (CSO) method using inverse Lagrangian dispersion theory to infer the two components of ecosystem respiration (aboveground and forest floor) from measured mean CO₂ concentration profiles within the canopy. This method required measurements of within-canopy mean velocity statistics and did not consider local thermal stratification. We propose a Eulerian version of the CSO method (CSO_E) to account for local thermal stratification within the canopy for momentum and scalars using higher-order closure principles. This method uses simultaneous mean CO₂ concentration and air temperature profiles within the canopy and velocity statistics above the canopy as inputs. The CSO_E was tested at a maturing loblolly pine plantation over a 3-year period with a mild drought (2001), a severe drought (2002), and a wet year (2003). Annual forest floor efflux modeled with CSO_E averaged 111 g C m^-2 less than that estimated using chambers during these years (2001: 1224 versus 1328 gCm^-2; 2002: 1127 versus 1230 gCm^-2; 2003: 1473 versus 1599 gCm^-2). The modeled ecosystem respiration exceeded estimates from eddy covariance measurements (uncorrected for storage fluxes) by at least 25%, even at high friction velocities. Finally, we showed that the CSO_E annual nighttime respiration values agree well with independent estimates derived from the intercept of the ecosystem light-response curve from daytime eddy covariance CO₂ flux measurements

   Keywords:
   atmospheric boundary layer;atmospheric composition;atmospheric temperature;