First-order chemistry in the surface-flux layer

L. Kristensen, C.E. Andersen, Hans Ejsing Jørgensen, P. Kirkegaard, K. Pilegaard

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    We have discussed the behavior of a non-conserved scalar in the stationary, horizontally homogeneous, neutral surface-flux layer and, on the basis of conventional second-order closure, derived analytic expressions for flux and for mean concentration of a gas, subjected to a first-order removal process, The analytic flux solution showed a clear deviation from the constant flux, characterizing a conserved scalar in the surface-flux layer. It decreases with height and is reduced by an order of magnitude of the surface flux at a height equal to about the typical mean distance a molecule can travel before destruction. The predicted mean concentration profile, however, shows only a small deviation from the logarithmic behavior of a conserved scalar. The solution is consistent with assuming a flux-gradient relationship with a turbulent diffusivity corrected by the Damkohler ratio, the ratio of a characteristic turbulent time scale and the scalar mean lifetime. We show that if we use only first-order closure and neglect the effect of the Damkohler ratio on the turbulent diffusivity we obtain another analytic solution for the profiles of the flux and the mean concentration which, from an experimental point of view, is indistinguishable from the first analytic solution. We have discussed two cases where the model should apply, namely NO which, by night, is irreversibly destroyed by interaction with mainly O-3 and the radioactive Rn-220. Only in the last case was it possible to find data to shed light on the validity of our predictions. The agreement seemed such that a falsification of our model was impossible. It is shown how the model can be used to predict the surface flux of Rn-220 from measured concentration profiles.
    Original languageEnglish
    JournalJournal of Atmospheric Chemistry
    Issue number3
    Pages (from-to)249-269
    Publication statusPublished - 1997


    • atmospheric surface layer
    • constant-flux layer
    • ozone
    • nitric oxide
    • radon
    • thoron
    • thoron exhalation
    • Damkohler ratio
    • eddy diffusivity


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