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对流层大气温度的垂直分布特征直接关联天气现象和大气污染物扩散,一直是气象和环境部门的重点观测对象。当前激光雷达技术已经成为探测对流层大气温度垂直分布和时间演变的有效手段。然而由于对流层中含有大量的气溶胶粒子,因此利用传统的振动拉曼和瑞利散射激光雷达技术测量大气温度具有一定的局限性,尤其是边界层内存在高浓度的气溶胶粒子会严重降低大气温度测量精度。采用纯转动拉曼激光雷达技术可有效降低气溶胶粒子对测量温度精度的影响。纯转动拉曼测温激光雷达的核心是分光单元设计,国内外研究普遍使用基于双光栅干涉仪的分光方法。文中将采用基于滤光片法的纯转动拉曼信号分光设计,相比而言该方法具有更高的分光效率,并且能够通过调节滤光片的角度改变激光雷达系统的灵敏度,操作更为简单。在中国科学院“大气灰霾追因与控制”先导专项支持下,该激光雷达与2014年11月安置在中国科学技术大学超级大气观测站。在亚太经济合作组织北京会议期间,展开大气环境测量试验。激光紫外波段能量约为200 m J,频率为20 Hz,激光脉冲数为5 000发,空间分辨率为7.5 m。实验结果表明,在晴朗无云气溶胶浓度较小的天气条件下温度测量统计误差小于1.5 K,测量高度可达10 km,在7.5 km以下统计误差小于1 K;在有薄云或者轻度雾霾天气条件下,温度测量统计误差在±3K左右,测量有效高度通常在6~8 km,在4.8 km以下统计误差小于1 K。
The vertical distribution of the tropospheric temperature directly correlates with the weather phenomenon and the diffusion of atmospheric pollutants. It has been the key observational object of the meteorological and environmental departments. Current laser radar technology has become an effective means of detecting the vertical distribution and temporal evolution of tropospheric atmospheric temperature. However, due to the large amount of aerosol particles in the troposphere, the use of traditional vibrational Raman and Rayleigh-scattering lidar techniques to measure atmospheric temperature has some limitations. In particular, the presence of high concentrations of aerosol particles in the boundary layer can severely degrade the atmosphere Temperature measurement accuracy. The purely rotating Raman lidar technology can effectively reduce the impact of aerosol particles on the measurement of temperature accuracy. Purely rotating Raman temperature measurement lidar is the core of the design of the spectroscopic unit, widely used at home and abroad based on the double grating interferometer spectroscopy method. In this paper, the filter based purely rotational Raman signal spectroscopy is adopted, which has a higher spectral efficiency and can change the sensitivity of the laser radar system by adjusting the angle of the filter, making the operation easier . The Lidar was placed with the Super Atmosphere Observation Station of the University of Science and Technology of China in November 2014 under the support of the Chinese Academy of Sciences under the pilot project “Atmospheric Haze Chase and Control”. During the Beijing conference of the Asia-Pacific Economic Cooperation (APEC), the atmospheric environment test was conducted. The energy of UV laser band is about 200 mJ, the frequency is 20 Hz, the number of laser pulses is 5000 and the spatial resolution is 7.5 m. The experimental results show that the statistical error of temperature measurement is less than 1.5 K under the condition of sunny cloudless aerosol, the measurement error is up to 10 km, and the statistical error is less than 1 K below 7.5 km. In the case of thin clouds or mild haze Under weather conditions, the statistical error of temperature measurement is about ± 3K, and the effective measurement height is usually 6 ~ 8 km. The statistical error under 1 km is less than 1 K under the condition of 4.8 km.