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消光系数和光散射系数之间的差异，现场测量环境气溶胶的光吸收系数作为相对湿度(RH)的函数。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颗粒消光系数的三波长光学消光池，用于综合野外实验。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相结合。将组装和测试一个完整的系统，包括消光电池、积分浊度计、基于滤光片的吸收光度计以及RH控制、数据采集等必要的辅助设备。随后，将在三个选定的气溶胶中具有显著光吸收碳浓度和分数的野外地点进行实地测量。初步选定的地点是：西雅图，华盛顿州，邦德维尔，伊利诺伊州，以及泰国的一个地点。在后两个地点，研究人员将与更大、更密集的实地活动合作，以利用其他研究小组进行的物理、化学和光学气溶胶测量。通过收集关于含“黑碳”气溶胶的详细的现场数据，这项工作将提供关于这些非常重要的气溶胶光学性质的更准确的信息。这些数据是建立地球-大气系统辐射收支模型所必需的。这项研究将与华盛顿大学和大气和海洋联合研究所的教学和外联活动结合起来。一名博士后科学家将通过该项目得到支持。

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.