Turbulent Dissipation Rate In The Boundary Layer Via UHF Wind Profiler Doppler Spectral Width Measurements
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The study is focused on the retrieval and validation of the turbulent kinetic energy dissipation rate εfrom spectral width measurements made by a UHF wind profiler in the convective atmospheric boundary layer. The possibility to deduce ε, which is one of the most important parameters for boundary-layer study and monitoring, from Doppler radar spectral width measurements has a firm theoretical basis established by numerous earlier works. However, the major drawback of this approach lies in various meteorological and instrumental sources of non-turbulent spectral width broadening which have to be recognised and accounted for. In the first part of the study, the theoretical background of the ε retrieval is detailed and all possible causes of spectral broadening are listed and evaluated. In the second part, the method is applied to four days of UHF diurnal boundary-layer observations, collected during the TRAC-98 experiment, for which in situ aircraft ε measurements were available. Comparison between radar-retrieved εand in situ aircraft measurements yields a fairly good agreement with a linear correlation coefficient of about 0.9 and a residual bias less than 2 × 10-4 m2 s-3. The analysis of εderived from vertical and off-zenith observation leads to the recommendation, that in the boundary layer, where the wind is usually moderate, data collected by off-zenith beams should be used. Indeed, the measurement of the vertical spectral width, less affected by the large-scale broadening factor, can still be altered by the ground clutter removal.
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