标题： 泰勒假设及其对林地采伐区通量测量的影响 显示英文标题

标题： Taylors hypothesis and its impact on flux measurements in a forest clearcut

摘要： 泰勒假设是将时间上的观测转换为湍流空间信息的支柱，而在微气象塔上进行湍流测量时使用。 为了验证其在高度异质的森林采伐地表的有效性，我们利用了广泛的分布式温度传感（DTS）和涡旋协方差（EC）数据集。 DTS测得的温度波动时空相关曲线用于计算在采伐地以上3.1米高度处浮力条件下的温度结构的整体对流速度。 这些对流速度与EC系统在采伐地中间测得的平均风速和顺流速度的湍流强度进行比较。 根据是否与森林边缘平行或垂直，和之间的关系显著不同。 然而，无论风向如何，惯性子区尺度的温度结构的对流速度随着波数的增加呈幂律变化。 这种幂律的指数不同于均质的大气表面层流动，从而指向异质性的影响。 尺度相关的对流速度非线性地将时间频率转换为顺流波数，这最终影响湍流（共）谱的特性。 更重要的是，这种非线性转换产生了一个关键频率极限，超过该极限后，从频率推导出的涡旋长度尺度小于声学风速仪的物理尺寸，因此无法被准确解析。 这个关键极限质疑了该频率以上的EC通量估计。 显示英文摘要

摘要： Taylors hypothesis is the backbone to convert observations done over time to spatial information of the flow while carrying out turbulence measurements on a micrometeorological tower. To address its validity over a highly heterogeneous forest clearcut surface, we utilize an extensive Distributed Temperature Sensing (DTS) and Eddy Covariance (EC) datasets. The DTS measured space-time correlation curves of temperature fluctuations are used to compute the bulk convective speeds of temperature structures in buoyant conditions at a height of 3.1 m above the clearing. These convective speeds are compared with the mean wind speed and turbulent intensities of streamwise velocities obtained from the EC system at the middle of the clearcut. Depending on if is parallel or perpendicular to the forest edge, the relationships between and are significantly different. However, irrespective of the wind direction, the convective speeds of temperature structures at inertial subrange scales behave in a power-law fashion with increasing wavenumbers. The exponent of this power-law differs from a homogeneous atmospheric surface layer flow, thereby pointing towards the effects of heterogeneity. The scale-dependent convective speeds non-linearly transform the temporal frequencies to streamwise wavenumbers, which, eventually, impacts the properties of turbulence (co) spectra. More importantly, this non-linear transformation yields a critical frequency limit, beyond which the eddy length scales derived from frequencies are smaller than the physical dimension of the sonic anemometers, and therefore, cannot be faithfully resolved. This critical limit questions the EC flux estimates beyond this frequency.