Estimating Momentum, Heat and Moisture Fluxes from Structure Parameters

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  • 1 Cooperative Institute for Research in Environmental Sciences, University of Colorado/N0AA, Boulder 80309 and Wave Propagation Laboratory, NOAA, Boulder, CO 80302
  • | 2 Wave Propagation Laboratory, NOAA, Boulder, CO 80302
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Abstract

A theory is developed for obtaining the vertical fluxes of momentum, heat and moisture in a quasi-steady, locally-homogeneous surface layer from measurements of the structure parameters of velocity, temperature and humidity. The momentum flux is shown to be generally more sensitive to measurement errors in the structure parameters and to uncertainties in certain turbulence parameters than are the heat and moisture fluxes. The structure parameters can, in principle, be obtained from path-averaged wave propagation measurements; for example, the temperature structure parameter CT2, is readily obtained from optical scintillations. It is estimated that in the case of CT2 a path-averaged optical measurement requires about 1% of the averaging time of a conventional measurement of CT2 under typical conditions.

Abstract

A theory is developed for obtaining the vertical fluxes of momentum, heat and moisture in a quasi-steady, locally-homogeneous surface layer from measurements of the structure parameters of velocity, temperature and humidity. The momentum flux is shown to be generally more sensitive to measurement errors in the structure parameters and to uncertainties in certain turbulence parameters than are the heat and moisture fluxes. The structure parameters can, in principle, be obtained from path-averaged wave propagation measurements; for example, the temperature structure parameter CT2, is readily obtained from optical scintillations. It is estimated that in the case of CT2 a path-averaged optical measurement requires about 1% of the averaging time of a conventional measurement of CT2 under typical conditions.

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