用于激光云高仪的微分增强云检测方法

激光云高仪是对大气中云的时空分布进行自动连续监测的有力工具之一,现有的云检测算法在低信噪比或有气溶胶影响时容易产生误判或漏判。文中分析了激光云高仪回波的原始信号、一阶微分信号和二阶微分信号特征,构造了两个新的信号序列,提出了一种微分增强云检测方法。该算法可以实现对云回波信号中云峰和云边界特征的增强和分离,有效修正了低信噪比和气溶胶层对云检测带来的误差。通过实验对比了微分增强法和微分零交叉法的云检测结果,结果表明:微分增强法在不影响云高判别的情况下,能有效地减少云的漏判和误判。

Laser ceilometer is one of the most powerful instruments to monitor the spatial and temporal distribution of cloud automatically and uninterruptedly. For the reason of algorithm, low signal-to-noise ratio and existence of aerosol layer may lead to inaccuracy during cloud observation. Based on the analyses to raw signal, differential signal and second-order differential signal, the differential enhancing method for detection of cloud was presented as well as the construction of two new signal series. The new method could realize the enhancement and separation of the signal feature of cloud peak and boundary and results in reduction of influence of low signal-to-noise ratio and existence of aerosol layer. Comparison experiments using both the differential zero-crossing method and the differential enhancing method were conducted. The results show the differential enhancing method can reduce the rates of missing judgement and misjudgement while has no influence to the judgement of cloud heights.