Real-time, wide field-of-view monitoring of the atmosphere by means of a novel imaging lidar system

大气气溶胶，特别是对流层气溶胶，通过辐射散射及其作为云凝结核的行为对气候产生重大影响。然而，它们在真实大气中的微观特性，迄今为止还没有从观测中完全掌握。超高能宇宙射线粒子的起源和传输是全天巡天高分辨率空气淋浴（Ashra）望远镜项目的研究对象。本研究项目在美国夏威夷岛部署了一套全半球观测望远镜阵列系统，将新型Ashra望远镜与激光雷达技术相结合，实现了对低层大气气溶胶和云层二维分布的实时监测。虽然在传统的单静态激光雷达观测中，发射激光系统和接收望远镜系统是同时配置的，但Ashra望远镜的高灵敏度使得可以分别定位发射和接收系统。这种双基地方法的优点是可以直接详细地监测地表附近气溶胶/云的分布。如果在望远镜探测视场区域固定的情况下对激光束进行扫描，则可以在前向散射区附近测量目标粒子的密度，该区域的散射强度通常比传统的后向散射区高得多。通过这个项目，我们充分检验了成像激光雷达系统的基本性能，并展示了其获取二维大气图像的能力。

Atmospheric aerosols, in particular, tropospheric aerosols significantly impact the climate through the scattering of radiation and their behavior as the cloud-condensation nuclei. Their microscopic properties in the real atmosphere, however, have not been fully grasped from observations so far. The origin and transportation of extremely high-energy cosmic-ray particles are investigated in the All-sky Survey High Resolution Air-shower (Ashra) telescope project. A telescope array system for the whole hemisphere observation is currently deployed on the Hawaii Island USA Iron the present research project, we have combined this novel Ashra telescope with lidar technique in order to achieve the real-time monitoring of two-dimensional distributions of aerosols and clouds in the lower atmosphere. Although a transmitting laser system and receiving telescope system are collocated in conventional mono-static lidar observations, the highly sensitive nature of the Ashra telescope makes it possible to locate the transmitter and receiver systems separately. This bistatic approach has the advantage that the aerosol/cloud distribution near the surface level can be directly monitored in detail. If the laser beam is scanned while the detection field-of-view sector of the telescope is fixed, the density of target particles can be measured in the vicinity of the forward-scattering regime, where the scattered intensity is generally much higher than the conventional, back-scattering regime. Through this project, we have fully checked the basic performance of our imaging lidar system, and have demonstrated its capability in obtaining the atmospheric images in a two-dimensional way.