Jet engine power loss due to ice particle accumulation is a recognized aviation hazard occurring in cloud conditions difficult to forecast or visually recognize. High-altitude cirrus clouds can have ice particle concentrations high enough to be dangerous; therefore, pilots must be informed when aircraft enter such environments. One approach to determining ice particle concentration is an onboard lidar system. Concurrent lidar measurements are compared to backscatter coefficients derived from particle size distributions obtained from wing-mounted, in situ probes during four case studies consisting of sixty-second flight segments at different temperatures: +7 and +4 ^∘C for water droplet analysis, and −33 and −46 ^∘C for ice particle analysis. Backscatter coefficients derived from external cloud probes (ECP) are correlated (0.91) with measurements by an airborne lidar system known as the Optical Ice Detector (OID). Differences between OID and ECP backscatter coefficients range from less than 1 to over 3 standard deviations in terms of uncertainties. The backscatter coefficients are mostly in agreement for liquid clouds and are in disagreement for the −33 and −46 ^∘C cases, with ECP-derived backscatter coefficients lower than the OID for three out of the four cases. Measurements over four 60 s research flight segments show that measured total water content is correlated (0.74) with the OID backscatter coefficient, which indicates that the OID is a useful instrument for determining ice particle concentrations over a broad range of environments, including at ice water contents as low as 0.02 g m⁻³. Additionally, concurrent measurements from cloud imaging probes and the OID provide improved knowledge of cloud conditions, which may help in understanding cloud processes.

中文翻译：

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将原位云探测器测量得出的反向散射系数与并发机载激光雷达进行比较的技术

由于冰颗粒积聚导致的喷气发动机功率损失是公认的航空危险，发生在难以预测或目视识别的云条件下。高空卷云的冰粒浓度高到足以造成危险；因此，当飞机进入此类环境时，必须通知飞行员。确定冰颗粒浓度的一种方法是机载激光雷达系统。在由不同温度下的 60 秒飞行段组成的四个案例研究中，将并发激光雷达测量值与从机翼安装的原位探头获得的粒度分布得出的反向散射系数进行比较：+ 7 和+ 4  ^∘ C 用于水滴分析，以及- 33 和-46  ^∘ C 用于冰粒分析。来自外部云探测器 (ECP) 的反向散射系数与称为光学冰探测器 (OID) 的机载激光雷达系统的测量值相关 (0.91)。就不确定性而言，OID 和 ECP 后向散射系数之间的差异范围从小于 1 到超过 3 个标准差。后向散射系数大多与液态云一致，而与− 33 和− 46  ^∘不一致C 种情况，在四种情况中的三种情况下，ECP 派生的后向散射系数低于 OID。对四个 60 年代研究飞行航段的测量表明，测得的总水含量与 OID 后向散射系数相关 (0.74)，这表明 OID 是一种有用的工具，可用于确定广泛环境中的冰颗粒浓度，包括在冰水中含量低至 0.02 g m ^-3。此外，来自云成像探测器和 OID 的并行测量提供了对云条件的改进知识，这可能有助于理解云过程。