激光雷达探测合肥云层高度方法研究及分析

Detection and analysis of cloud height in Hefei with lidar

为了通过雷达回波信号廓线图准确确定云底、云峰、云顶高度,采用微分识别法着重分析了多峰时如何判别单层云和多层云,介绍了雷达结构系统,讨论了2008年5月期间合肥地区云层的高度、厚度、光学厚度的激光雷达探测结果,并进行了理论分析和实验验证。为验证方法的可行性,将雷达和芬兰Vaisala云高仪(探测距离0km～7km)对准同一片云,取得了实测数据,并进行了对比分析。结果表明,用微分法所得云高数据与Vaisala在7km以下较吻合,7km以上所测的卷云和SAGEⅡ所测的卷云高度基本一致,且实验所测合肥上空的高层卷云基本上都是薄卷云,云峰主要分布在9km～12km范围之内。这一结果对以后研究云层高度反演、并与卫星数据进行校验对比是有帮助的。

In order to determine the cloud base, cloud peak and cloud top from the lidar backscatter profile, the differential retrieval method was put forward. The study was focused on distinguishing the single layer from the multi-layer cloud when confronted several backseatter signal peaks. The structure of the lidar used in the experiment was introduced; then the cloud height, cloud thickness and cloud optical depth detected from the lidar in May in Hefei was investigated. The related theory analysis and experiment were presented. In order to test the feasibility of the cloud detection approach, the results obtained from the lidar were compared with those obtained from Finland ceilometer Vaisala （detecting range： 0km -7km） after both the instruments aiming at the cloud in the same region. Resuhs show that the data below 7kin were identical; the data above the 7km were consistent with those from satellite SAGE 1[. The high layer clouds detected in Hefei, also called cirrus, were mostly thin cirrus with the cloud peak varying from 9km to 12km. The method of cloud detection is helpful for the future cloud retrieval and satellite validation.