Displaced-Beam Small Aperture Scintillometer Test. Part Ii: Cases-99 Stable Boundary-Layer Experiment |
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| Authors: | O K Hartogensis H A R De Bruin B J H Van De Wiel |
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| Institution: | (1) Meteorology and Air Quality Group, Wageningen University, Duivendaal 2, 6701 AP Wageningen, The Netherlands |
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| Abstract: | The performance of the Scintec displaced-beam small aperture scintillometer (DBSAS) in the stable boundary layer (SBL) is investigated using data gathered during the CASES-99 experiment in Kansas, U.S.A. The DBSAS is superior to the eddy-covariance method in determining vertical fluxes of sensible heat and momentumclose to the ground and/or over short (< 1 min) averaging intervals. Both aspects are of importance in the shallow and non-stationary SBL.The friction velocity, u*, the temperature scale,  *, and from these the sensible heat flux, H, were calculated from the indirectly determined dissipation rate,  , and the structure parameter of temperature, CT
2, by the DBSAS, which was operated over a path length of 112 m. All these variables are compared with eddy-covariance data for 10-minute time averages. Previously reported systematic errors in the DBSAS, overestimation of u* for low u* values and underestimation of u* for high u* values, have in part been dealt with by adjusting the beam displacement distance from 2.7 mm to 2.6 mm in the calculations. The latter adjustment is presented as a working hypothesis, not a general solution. |
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| Keywords: | CASES-99 Dissipation rate Fluxes Scintillometer Stable boundary layer Structure parameter |
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