Liu Alan Z, Guo Yafang
Appl Opt. 2016 Nov 20;55(33):9467-9475. doi: 10.1364/AO.55.009467.
Na lidar can measure vertical wind and temperature at high temporal and vertical resolutions, enough to resolve gravity wave perturbations. Heat flux due to dissipating gravity waves is an important quantity that can be derived from such perturbations. When lidar signals are high, a photomultiplier tube (PMT) used to count incoming photons may suffer from the saturation effect, and its output count is not linearly related to incoming photon counts. Corrections to this effect can be measured in a laboratory setting but may have large errors at high count rates. We show that the errors in the PMT correction can cause significant bias in the heat flux calculation due to the inherent correlation between wind and temperature errors. Using the measurements made by Na lidar at the Andes Lidar Observatory with Hamamatsu PMTs, we developed a calibration procedure to remove such PMT correction errors from laboratory measurements. By applying the revised PMT correction curve we demonstrated that the heat flux bias can be removed through this procedure.
钠激光雷达能够以高时间分辨率和垂直分辨率测量垂直风速和温度，足以解析重力波扰动。因重力波耗散产生的热通量是一个重要的量，可从此类扰动中推导得出。当激光雷达信号很强时，用于计数入射光子的光电倍增管（PMT）可能会受到饱和效应的影响，其输出计数与入射光子计数并非线性相关。这种效应的校正可以在实验室环境中测量，但在高计数率下可能会有较大误差。我们表明，由于风速和温度误差之间的内在相关性，PMT校正中的误差会在热通量计算中导致显著偏差。利用安第斯激光雷达天文台使用滨松PMT的钠激光雷达测量数据，我们开发了一种校准程序，以消除实验室测量中的此类PMT校正误差。通过应用修正后的PMT校正曲线，我们证明了通过此程序可以消除热通量偏差。
