[H-TT17] Environmental Remote Sensing

[HTT17-P06] Meteorological and environmental observations of the near-surface atmosphere by an ultraviolet lidar system

*Masanori Yabuki¹, Kazuhiko Miura^2,3, Hiroaki Kuze⁴, Kazuto Matsuki⁵, Yuichi Uchiho⁵, Eiji Takeuchi⁵, Toshikazu Hasegawa⁵ (1.Kyoto University, 2.Tokyo University of Science, 3.Laboratory for Environmental Research at Mount Fuji, 4.Chiba University, 5.EKO Instruments Co., Ltd.)

Keywords:Ultraviolet lidar system, Meteorological and environmental observations

Understanding the processes of energy and mass exchange between the atmosphere and the Earth’s surface is essential to understand the urban heat island effect, localized torrential rain processes, and dynamics of the atmospheric pollutants associated with human life and health. We developed lidar techniques using an ultraviolet laser to observe the thermodynamic profiles and atmospheric pollutants. A rotational and vibrational Raman lidar system using a laser at a wavelength of 266 nm was constructed for continuous monitoring of temperature and water vapor. The use of deep ultraviolet wavelengths is convenient because of the low background noise during the daytime since, at those wavelengths, most of the solar radiation is absorbed by the ozone layer in the stratosphere. The newly developed optical system of our rotational Raman lidar comprises a double-grating spectrometer and photomultiplier tube array. This configuration determines the shape of the rotational Raman spectrum with easy optical alignment, reducing the influence of laser wavelength instability. We evaluated our Raman lidar data by comparing them with radiosonde observations at the Shigaraki MU observatory. In addition, we conducted a simultaneous operation of the temperature lidar with a WindCube v2 Doppler wind lidar manufactured by Leospher and provided by EKO Instruments Co., Ltd. (Japan) for studying the atmospheric structure up to altitudes of 200 m.

We constructed a mobile vehicle lidar for continuously monitoring atmospheric aerosols with high spatiotemporal resolutions. The lidar employed a laser with a wavelength of 355 nm. After passing through the beam expander, the outgoing laser energy satisfied the eye-safety requirements. Furthermore, a 360° obstacle detection sensor and mechanical beam shutter suspended laser emission when an overpass structure was detected in the vehicle’s travel direction. We developed wedge prism optics for attaining near-range observation, resulting in the near-measurable range from 7 m. The lidar was installed on an anti-vibration pallet in a car, and approximately 48 hours of non-powered continuous operation could be performed while driving. Through round-trip observations, we measured the spatial distribution of aerosols above roads surrounded by high-rise buildings, on bay bridges, and on several hundred kilometers between Kansai and Kanto. In this paper, we present the characteristics of aerosol distribution in the atmospheric boundary layer, including the surface inversion layer, observed using a mobile vehicle lidar in Tokyo, mainly in the transitional season from autumn to winter.