Development of a portable water vapor profiler in the lower troposphere using a small Raman lidar

我们研制了一台用于水汽廓线探测的便携式拉曼激光雷达，该雷达位于L波段风廓线雷达的下限200m左右。用倍频为532 nm的小激光进行传输，利用35.5 cm望远镜，用光子计数系统接收到相同波长(532 Nm)、N_2拉曼(607 Nm)和H_20拉曼(660 Nm)的散射体。水汽混合比在200米左右白天黑夜都能观测到，该系统长期安装在日本滋贺茂名MU天文台。系统校准系数在4-5%的偏差范围内连续6个多月没有变化。除了罕见的低海拔云或雾之外，大多数时候水蒸气的轮廓都很好。当我们调整系统以使用更大的虹膜时，可以在3-4公里的高度观察到水汽混合比剖面。这台激光雷达已经经过改进，可以通过网络进行远程控制。另一方面，在水平方向上进行了观测，并在车辆上进行了现场观测。我们发现茂名观测站周围国家森林上空的波动水汽波动高达10%，并与气溶胶强度相关。Nakadake火山喷发气体中水蒸气含量的测定ASO成功开展，这是首次对火山气中H20进行遥感测量。如上所述，作为一种小型拉曼激光雷达的应用，这项研究取得了比我们一开始预期的更多的成果。

We have developed a transportable Raman lidar for water vapor profiling at around 200 m altitude, which is the lower boundary of a L-band wind profiler radar. A small Nd:YAG laser with a SHG of 532 nm is used for transmission and the same wavelength (532 nm), N2 Raman (607 nm) and H20 Raman (660 nm) scatters are received with a photon counting system, by means of a 35.5 cm telescope. The water vapor mixing ratio around 200 m could be observed both day and night, and the system was equipped at the Shigaraki MU observatory, Shiga, Japan for a long time. The system calibration factor did not change for more than 6 months within a deviation of 4 - 5 %. Water vapor could be profiled well for most of the times except for a rare case of the low altitude clouds or fogs. When we adjust the system to use a larger iris, water vapor mixing ratio profiles could be observed up to 3 - 4 km altitude. This lidar has been improved to be controlled remotely through a network. On the other hand, observations in a horizontal direction as well as a field observation on board a vehicle have been carried out. We found that fluctuations of waver vapor as large as 10 % over the national forest around Shigaraki observatory, as well as correlation with aerosol intensity. The measurement of water vapor content in the volcanic gas emitted from Nakadake, Mt. Aso has been successfully carried out, which is the first time of the remote-sensing measurement of H20 in the volcanic gas. As mentioned above, this study has achieved much more than we had expected at the beginning, as an application of a small Raman lidar.