A Large-Eddy Simulation Study of Water Vapour and Carbon Dioxide Isotopes in the Atmospheric Boundary Layer
- 402 Downloads
A large-eddy simulation model developed at the National Center for Atmospheric Research (NCAR) is extended to simulate the transport and diffusion of C18OO, H218O and 13CO2 in the atmospheric boundary layer (ABL). The simulation results show that the 18O compositions of leaf water and the ABL CO2 are moderately sensitive to wind speed. The variations in the 18O composition of water vapour are an order of magnitude greater than those in the 13C and 18O compositions of CO2 both at turbulent eddy scales and across the capping inversion. In a fully-developed convective ABL, these isotopic compositions are well mixed as with other conserved atmospheric quantities. The Keeling intercepts determined with the simulated high-frequency turbulence time series do not give a reliable estimate of the 18O composition of the surface water vapour flux and may be a reasonable approximation to the 13C and 18O compositions of the surface CO2 flux in the late afternoon only after a deep convective ABL has developed. We suggest that our isotopic large-eddy simulation (ISOLES) model should be a useful tool for testing and formulating research hypotheses on land–air isotopic exchanges.
KeywordsIsotopes Keeling plot Kinetic fractionation Land-surface model Large-eddy simulation
Unable to display preview. Download preview PDF.
- Barbour MM, Fischer RA, Sayre KD, Farquhar GD (2000) Oxygen isotope ratio of leaf and grain material correlates with stomatal conductance and grain yield in irrigated wheat. Aust J Plant Physiol 27: 625–637Google Scholar
- Chen B, Chen JM, Tans PP, Huang L (2006) Simulating dynamics of 13C of CO2 in the planetary boundary layer over a boreal forest region: covariation between surface fluxes and atmospheric mixing. Tellus 58B: 537–549Google Scholar
- Craig H, Gordon LI (1965) Deuterium and oxygen-18 variations in the ocean and the marine atmosphere. In: Tongiorgi E (ed) Stable isotopes in oceanographic studies and paleotemperatures. Lab di Geol Necl, Pisa, pp 9130Google Scholar
- Helliker BR, Berry JA, Betts AK, Bakwin PS, Davis KJ, Denning AS, Ehleringer JR, Miller JB, Butler MP, Ricciuto DM (2004) Estimates of net CO2 flux by application of equilibrium boundary layer concepts to CO2 and water vapor measurements from a tall tower. J Geophys Res 109: D20106. doi:10.1029/2004JD004532 CrossRefGoogle Scholar
- Lai C, Schauer A, Owensby C, Ham J, Helliker B, Tans P, Ehleringer J (2006) Regional CO2 fluxes inferred from mixing ratio measurements: estimates from flask air samples in central Kansas, USA. Tellus 58B: 523–536Google Scholar
- Lee X, Smith R, Williams J (2006) Water vapor 18O/16O isotope ratio in surface air in New England, USA. Tellus 58B: 293–304Google Scholar
- Lloyd J, Francey R, Mollicone D, Raupach M, Sogachev A, Arneth A, Byers J, Kelliher F, Rebmann C, Valentini R, Wong S, Bauer G, Schulze E (2001) Vertical profiles, boundary layer budgets, and regional flux estimates for CO2 and its 13C/12C ratio and for water vapor above a forest/bog mosaic in central Siberia. Glob Biogeochem Cycles 15: 267–284CrossRefGoogle Scholar
- Ogée J, Peylin P, Ciais P, Bariac T, Brunet Y, Berbigier P, Roche C, Richard P, Bardoux G, Bonnefond JM (2003) Partitioning net ecosystem carbon exchange into net assimilation and respiration using 13CO2 measurements: a cost-effective sampling strategy. Glob Biogeochem Cycles 17: 1070. doi:10.1029/2002GB001995 CrossRefGoogle Scholar
- Ogée J, Peylin P, Cuntz M, Bariac T, Brunet Y, Berbigier P, Richard P, Ciais P (2004) Partitioning net ecosystem carbon exchange into net assimilation and respiration with canopy-scale isotopic measurements: an error propagation analysis with 13CO2 and C18OO data. Glob Biogeochem Cycles 18: GB2019CrossRefGoogle Scholar