On 20 and 22 August 2019, a small tripod was outfitted with a sonic anemometer and placed in a highway shoulder to compare with measurements made on an instrumented car as it traveled past the tripod. The rural measurement site in this investigation was selected so that the instrumented car traveled past many upwind surface obstructions and experienced the occasional passing vehicle. To obtain an accurate mean wind speed and mean wind direction on a moving car, it is necessary to correct for flow distortion and remove the vehicle speed from the measured velocity component parallel to vehicle motion (for straight-line motion). In this study, the velocity variances and turbulent fluxes measured by the car are calculated using two approaches: (1) eddy covariance and (2) wavelet analysis. The results show that wavelet analysis can better resolve low frequency contributions, and this leads to a reduction in the horizontal velocity variances measured on the car, giving a better estimate for some measurement averages when compared to the tripod. A wavelet-based approach to remove the effects of sporadic passing traffic is developed and applied to a measurement period during which a heavy-duty truck passes in the opposite highway lane; removing the times with traffic in this measurement period gives a reduction of approximately 10 % in the turbulent kinetic energy. The vertical velocity variance and vertical turbulent heat flux measured on the car are biased low compared to the tripod. This low bias may be related to a mismatch in the flux footprint of the car versus the tripod or perhaps to rapid flow distortion at the measurement location on the car. When random measurement uncertainty is considered, the vertical momentum flux is found to be consistent with the tripod in the 95 % confidence interval and statistically different than 0 for most measurement periods.

中文翻译：

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农村环境中装有仪表的移动汽车的平均风、方差和协方差的测量

2019 年 8 月 20 日至 22 日，一个装有声波风速计的小型三脚架被放置在高速公路路肩上，以与一辆经过三脚架的仪表汽车进行的测量结果进行比较。本次调查选择农村测量点，使仪器车行驶经过多个逆风面障碍物，并经历偶尔经过的车辆。为获得移动汽车的准确平均风速和平均风向，有必要校正流动畸变并从平行于汽车运动（对于直线运动）的测得速度分量中去除车速。在这项研究中，使用两种方法计算汽车测量的速度变化和湍流通量：(1) 涡协方差和 (2) 小波分析。结果表明，小波分析可以更好地解决低频贡献，这导致汽车上测量的水平速度变化减少，与三脚架相比，可以更好地估计某些测量平均值。开发了一种基于小波的方法来消除零星过往交通的影响，并将其应用于重型卡车在对面高速公路车道上通过的测量期间；除去该测量期间的交通时间，湍流动能减少了大约 10%。与三脚架相比，在汽车上测得的垂直速度变化和垂直湍流热通量偏低。这种低偏差可能与汽车与三脚架的通量足迹不匹配有关，或者可能与汽车测量位置处的快速流动畸变有关。当考虑随机测量不确定性时，发现垂直动量通量在 95% 置信区间内与三脚架一致，并且在大多数测量期间统计上不同于 0。