Impact of density fluctuations on flux measurements of trace gases: Implications for the relaxed eddy accumulation technique
✍ Scribed by E. Pattey; R. L. Desjardins; F. Boudreau; P. Rochette
- Publisher
- Springer
- Year
- 1992
- Tongue
- English
- Weight
- 486 KB
- Volume
- 59
- Category
- Article
- ISSN
- 0006-8314
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✦ Synopsis
A simple and fast approach to determine when density fluctuations are non-negligible in the calculation of the flux of trace gases (Fe) is proposed. The correction (Fc -Fc(raw)), when expressed as the percentage of the flux, is dependent on the ratio of background concentration of the trace gas over its flux (E/F& on the partitioning of available energy between sensible (Fr) and latent (F,) heat fluxes, and on the flux measuring system. An increase from 100 to 200 W mm2 in available energy and from 0 to 20% in F&F, + F,) led to a threefold reduction in the required value of z/F, to have a density correction of 10%. A trace gas with a 1 Fc l/E value above 0.014 m s-l has a density correction on flux of less than lo%, for even the worst case scenario. Values of Fe/z for several trace gases computed from typical situations show that the fluxes of N20, NO, C02, C& and 0s need to be corrected, while those of pesticides and volatile organic compounds, for example, do not. The corrections required with the newly developed relaxed eddy accumulation technique are discussed and equation development is shown for two sampling systems.