A Method for Estimating the Turbulent Kinetic Energy Dissipation Rate from a Vertically Pointing Doppler Lidar, and Independent Evaluation from Balloon-Borne In Situ Measurements
A Method for Estimating the Turbulent Kinetic Energy Dissipation Rate from a Vertically Pointing Doppler Lidar, and Independent Evaluation from Balloon-Borne In Situ Measurements
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DOI：
10.1175/2010jtecha1455.1
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发表时间：
2010-10-01
影响因子：
2.2
通讯作者：
Brooks, Barbara J.
中科院分区：
文献类型：
--
作者：
O'Connor, Ewan J.;Illingworth, Anthony J.;Brooks, Barbara J.
通过与来自球载声波风速计的独立测量值进行比较，评估了一种从具有高时间和空间分辨率的垂直指向多普勒激光雷达估计耗散率的方法。该方法利用了来自多个连续样本的平均多普勒速度的方差，并且需要对水平风速的估计。噪声对方差的贡献可以从观察到的信噪比估计，并在适当的情况下去除。噪声方差与观测方差的相对大小提供了检索置信度的度量。与来自球载声波风速计的原位耗散率的比较表明，这种特殊的多普勒激光雷达是能够检索耗散率的范围内的至少三个数量级的magnesium.This方法是最适合的对流混合边界层内的耗散率的检索的运动尺度，多普勒激光雷达探头保持良好的惯性子范围内。在更静态的条件下估计耗散率时必须谨慎。对于这里描述的特定多普勒激光雷达，选择适当短的积分时间将允许该方法适用于这种情况，但以牺牲多普勒速度估计的准确性为代价。这里提出的两个案例研究表明，每4秒的配置文件，可靠的估计可以得出的范围内的至少一个数量级的几乎所有的最低2公里，在对流边界层，在50%。将单个剖面的积分时间增加到30 s可以大大提高精度，但可能会将检索限制在对流边界层内。因此，对于特定的实施方式，可能需要优化某些仪器参数。
A method of estimating dissipation rates from a vertically pointing Doppler lidar with high temporal and spatial resolution has been evaluated by comparison with independent measurements derived from a balloon-borne sonic anemometer. This method utilizes the variance of the mean Doppler velocity from a number of sequential samples and requires an estimate of the horizontal wind speed. The noise contribution to the variance can be estimated from the observed signal-to-noise ratio and removed where appropriate. The relative size of the noise variance to the observed variance provides a measure of the confidence in the retrieval. Comparison with in situ dissipation rates derived from the balloon-borne sonic anemometer reveal that this particular Doppler lidar is capable of retrieving dissipation rates over a range of at least three orders of magnitude.This method is most suitable for retrieval of dissipation rates within the convective well-mixed boundary layer where the scales of motion that the Doppler lidar probes remain well within the inertial subrange. Caution must be applied when estimating dissipation rates in more quiescent conditions. For the particular Doppler lidar described here, the selection of suitably short integration times will permit this method to be applicable in such situations but at the expense of accuracy in the Doppler velocity estimates. The two case studies presented here suggest that, with profiles every 4 s, reliable estimates of epsilon can be derived to within at least an order of magnitude throughout almost all of the lowest 2 km and, in the convective boundary layer, to within 50%. Increasing the integration time for individual profiles to 30 s can improve the accuracy substantially but potentially confines retrievals to within the convective boundary layer. Therefore, optimization of certain instrument parameters may be required for specific implementations.