Development of Instrumentation to Measure Atmospheric Light Extinction and its Scattering and Absorption Components

在短波光学领域，缺乏足够的仪器阻碍了各种研究领域的科学进步。大气中光的消光、散射和吸收的局部测量可以应用于以下几个科学问题：气溶胶辐射强迫及其对气候变化的影响。使用主动或被动系统的光学遥感。区域空气质量研究所需的大气能见度。主要研究人员将开发能够测量大气总光消光及其散射和吸收成分的仪器。该系统包括三个具体的仪器：(1)消光仪，将几十公里的光路折叠成1米长的光腔，通过测量光腔内光功率的指数衰减来确定消光。(2)一种基于逆浊度计概念的散射仪新概念，它可以收集几乎所有的散射光，包括大颗粒的前向散射。(3)利用共振光声检测光吸收，实时测量光吸收的光吸收仪器。全固态激光器的使用使得该仪器比之前的仪器更紧凑，耗电量更少。创新的声学设计使这款仪器比以前的设计更敏感一个数量级。拟议的这些仪器的发展将形成一组仪器，这将比单独使用的三种仪器有用得多。例如，吸收和散射测量相结合可以确定单散射气溶胶反照率。消光仪的加入将使大气光消光及其散射和吸收分量的实验问题得到圆满解决。这种封闭性对于质量保证是极其重要的，即通过检查测量的吸收和散射消光之和是否等于测量的消光，可以直接评估测量精度。

In the shortwave optical regions, lack of adequate instrumentation hinders scientific progress across a variety of research areas. The local measurement of light extinction, scattering and absorption in the atmosphere has applications to a number of scientific problems related to:1. Aerosol radiative forcing and its influence on climate change.2. Optical remote sensing using either active or passive systems.3. Atmospheric visibility as needed for regional air quality studies.The Principal Investigators will develop instrumentation capable of measuring total atmospheric light extinction and its scattering and absorption components. The system to be developed includes three specific instruments:(1) An extinction instrument which folds several tens of kilometers of optical path into a one-meter length optical cavity and determines extinction by measuring the exponential decay of the optical power contained in the cavity. (2) A novel scattering instrument concept based on the inverse nephelometer concept which collects virtually all scattered light including the forward scattering from large particles. (3) A light absorption instrument which yields a real time in situ measurement of optical light absorption by utilizing resonant photoacoustic detection of light absorption. The use of an all-solid-state laser makes this instrument much more compact and less power hungry than its predecessors. Innovative acoustic design makes this instrument more than an order of magnitude more sensitive than previous designs. The proposed development of these instruments will result in an instrument cluster which will be far more useful than the three individual instruments used separately. For example, the combination of absorption and scattering measurements can determine the single-scattering aerosol albedo. Addition of the extinction instrument will result in experimental closure on the problem of atmospheric light extinction and its scattering and absorption components. This closure is extremely important for quality assurance purposes, i.e., measurement accuracy can directly be assessed by checking if the sum of measured absorption and scattering extinction equals the measured extinction.