Documents published in Scipedia

• Evaluation of alternatives for parameterization of momentum and water vapor roughness lengths in lakes

  B. Solheid, N. Dias, F. Armani, D. Junior

  Rev. int. métodos numér. cálc. diseño ing. (2020). Vol. 36, (2), 30

  
  

  Abstract

  An assessment of the performance of various parameterization alternatives for roughness lengths of momentum and water vapour was performed. The micrometereological data used in this work was measured in the Itaipu reservoir, Brazil. Four models was tested for momentum roughness length, and four for water vapour. The parameterization for horizontal momentum flux are based on the Charnock equation and generalizations while the water vapour model are based on equations proposed by Brutsaert. The four models for momentum flux produced very similar results, in terms of goodness of fit and errors, and turned out only weakly dependent on friction velocity. Already the parameterizations for water vapor produced more dispersed results, and the best parameterizations found very poorly depend on the Reynolds roughness number, or are independent of it. Both in the case of momentum and water vapour, the optimal parameter values? of each parameterization found for Itaipu are significantly larger than those reported in the literature.

  Abstract
  An assessment of the performance of various parameterization alternatives for roughness lengths of momentum and water vapour was performed. The micrometereological data used [...]

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• Evaluation of the optical contamination of open path CO2 gas analyzers in measurements on a freshwater surface

  F. Armani, N. Dias, D. Junior

  Rev. int. métodos numér. cálc. diseño ing. (2020). Vol. 36, (1), 11

  
  

  Abstract

  Measurements of air-sea CO₂ fluxes with Eddy Covariance (EC) are generally affected by the optical contamination of open path gas analyzers. Since the conditions of saltwater environments may be similar to those of freshwater environments, in this work we evaluate whether this contamination is occurring in the LI-7500 open path CO₂ gas analyzer (''LI-COR Biosciences Ltd''), used in an experiment to measure greenhouse gas fluxes over the reservoir of the Itaipu Hydroelectric Power Plant. We evaluated the optical contamination indicators in the CO₂ measurements and two corrections for this: the numerical method called PKT method, proposed for CO₂ flux correction over ocean, and a multiple linear regression model. We find that the PKT method does not produce physically plausible results and that, contrary to what has been reported in ocean measurements, the measurements of the Itaipu experiment suffer less interference in more humid conditions. CO₂ correction by the regression model preserved the pattern of CO₂ flux daily variation, but it attenuated the magnitude of the fluxes: the average of the uncorrected fluxes was <math>-24.35</math>μgm^-2s^-1, while the average of the fluxes corrected by the statistical model was <math>-11.73</math>μgm^-2s^-1.

  Abstract
  Measurements of air-sea CO₂ fluxes with Eddy Covariance (EC) are generally affected by the optical contamination of open path gas analyzers. Since the [...]

  • 129
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