Measurement of Light Extinction and Scattering by Aerosols for Deriving the Wavelength and Humidity Dependence of Absorption and Single Scatter Albedo

该项目的目标是通过测量光消和光散射系数之间的差异，对环境气溶胶的光吸收系数作为相对湿度（RH）的函数进行现场测量。测量将在可见光范围内的三个波长（约450、550和700纳米）和相对湿度范围内进行。在现有原型的基础上，将开发一种能够测量环境气溶胶粒子消光系数的三波长光学消光单元，用于综合现场实验。积分浊度计将提供光散射系数。湿度控制系统将与第二个光学消光单元和浊度计结合使用。将组装和测试一个完整的系统，包括消光单元、集成浊度计、滤光片吸收光度计和必要的RH控制、数据采集等配套设备。随后，将在三个选定的具有显著吸光碳浓度和气溶胶中碳含量的地点进行实地测量。暂定的地点是：华盛顿州西雅图、伊利诺伊州邦迪维尔和泰国的一个地点。在后两个地点，研究人员将与更大规模、更密集的实地活动合作，利用其他研究小组进行的物理、化学和光学气溶胶测量。通过收集含有“黑碳”的气溶胶的详细现场数据，这项工作将为这些非常重要的气溶胶的光学特性提供更准确的信息。这些数据是建立地球-大气系统辐射收支模型所需要的。这项研究将与华盛顿大学和大气与海洋联合研究所的教学和推广活动结合起来。本项目将资助一名博士后科学家。

The goal of this project is to make in situ measurements of the light absorption coefficient for ambient aerosols as a function of relative humidity (RH) by measuring the difference between the coefficients of light extinction and light scattering. Measurements will be made at three wavelengths in the visible range (ca. 450, 550 and 700 nm) and over a range of relative humidities. A three-wavelength optical extinction cell capable of measuring the extinction coefficient of ambient aerosol particles for use in integrated field experiments will be developed, based on an existing prototype. An integrating nephelometer will provide the light scattering coefficient. A humidity control system will be incorporated with a second optical extinction cell and the nephelometer. A complete system consisting of extinction cells, integrating nephelometers, filter-based absorption photometers and necessary supporting equipment for RH control, data acquisition, etc. will be assembled and tested. Subsequently, field measurements will be carried out at three field sites selected to have significant light absorbing carbon concentration and fraction in the aerosol. The sites tentatively selected are: Seattle, WA, Bondville, IL, and a site in Thailand. At the latter two sites the investigators will collaborate with larger, intensive field campaigns to take advantage of the physical, chemical and optical aerosol measurements made by other research groups. By gathering detailed in situ data on "black carbon"-containing aerosols, this work will provide more accurate information on the optical properties of these very important aerosols. These data are needed for models of the radiation budget of the earth-atmosphere system. The research will be integrated with teaching and outreach activities at the University of Washington and the Joint Institute for the Study of the Atmosphere and Oceans. A post- doctoral scientist will be supported through this project.