MRI: Development of a Photo-Acoustic Light Absorption and Albedo Spectrometer for the Characterization of Aerosol Radiative Transfer in the Solar Spectrum

MRI：开发光声光吸收和反照率光谱仪，用于表征太阳光谱中的气溶胶辐射传输

• 批准号: 1040046
• 负责人: Hans Moosmuller
• 金额: $ 64.98万
• 依托单位: Nevada System of Higher Education, Desert Research Institute
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-10-01 至 2014-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1040046&HistoricalAwards=false
• 关键词: MRI; Development; Photo; Acoustic; Light

The goal of this project is to develop a novel Photoacoustic Aerosol Light Absorption and Albedo Spectrometer (PALAAS) for real time, in situ, first principle measurement of aerosol light absorption, scattering, and single scattering albedo spectra. Applications of PALAAS will include research into the optical properties of (1) brown carbon, which is emitted in large quantities by smoldering biomass burning and has largely unknown optical properties; (2) mineral dust, which by mass is the dominant ambient aerosol, and has a complex absorption spectrum; and (3) the connection between aerosol absorption spectra and modification of snow and ice surface albedo spectra due to aerosol deposition.Intellectual merit: Atmospheric aerosols and their radiative forcing cause the largest uncertainties in understanding and modeling global and regional climate change. Additional uncertainties are caused after aerosol deposition on snow and ice surfaces due to surface albedo modification. Common filter measurements of aerosol light absorption coefficients suffer from a large number of systematic errors; single wavelength photoacoustic measurements of aerosol light absorption coefficients are insufficient to characterize the radiative impact of aerosols with a strong and unknown wavelength dependence of absorption (e.g., brown carbon and mineral dust aerosols), which may make a very significant contribution to atmospheric aerosol absorption and to the lowering of aerosol single scattering albedo, a key quantity in aerosol radiative forcing. In addition, optical satellite remote sensing is needed for global, spatially-, and time-resolved coverage of aerosol radiative forcing because of the large spatial and temporal inhomogeneities of ambient aerosol concentration and optics. However, detailed knowledge of aerosol absorption spectra is needed for satellite monitoring. PALAAS will utilize a novel broadband super continuum laser covering the solar spectral range from 400 to 2000 nm for simultaneous measurement of aerosol light absorption and scattering coefficients and aerosol single scattering albedo in 32 customizable spectral bands, thereby increasing the number of bands by about one order of magnitude over state-of-the-art three-wavelength photoacoustic instruments. Simultaneous absorption and scattering measurements in these 32 bands will be enabled using a prism pulse compressor to (1) spatially separate the super continuum spectrum, (2) modulate each spectral band at an individual acoustic frequency with a custom optical chopper, (3) recombine the spectrum into a laser beam, and (4) send the laser beam through a photoacoustic resonator. Measurements of the scattering coefficient with a scattering sensor in the photoacoustic instrument and the absorption coefficient with the photoacoustic instrument can be achieved for all 32 wavelength bands simultaneously by decoding modulation frequencies with fast Fourier transform (FFT) analysis. This instrument will be potentially transformative for the field of aerosol optics, radiative forcing, and satellite remote sensing by providing the first real time, in situ, first principle measurements of aerosol light absorption, scattering, and albedo spectra.Broader impacts: Due to the uncertainties in radiative forcing and climate change modeling caused by aerosols and their poorly known optical properties, it is more challenging to predict global and regional climate change, formulate and put into place mitigation strategies, and convince society of the accuracy of scientific predictions in the face of these uncertainties. Therefore, the intellectual merits discussed above will have important broader societal impacts in the context of climate change affecting humanity. An educational component will involve high school, undergraduate, graduate, and postdoctoral students, specifically targeting underrepresented groups. In particular, the project will provide research experiences for (1) a diverse group of high school students through an existing partnership with the Washoe County School District Gifted and Talented Program; (2) undergraduate and graduate students through inclusion in formal classes at the University of Nevada, Reno, student employment, senior thesis, and Ph.D. dissertations; and (3) employment of a postdoctoral research associate participating in the instrument development. The postdoc will be mentored by the project PIs in instrument development, aerosol spectroscopy, and interdisciplinary environmental research.Instrument categorization: The Photoacoustic Aerosol Light Absorption and AlbedoSpectrometer will be developed to expand research capabilities in the area of aerosol shortwave radiative transfer with applications to climate change and satellite remote sensing research.

本项目的目标是研制一种新型的光声气溶胶光吸收和反照率光谱仪（PALAAS），用于气溶胶光吸收、散射和单次散射光谱的真实的实时、原位、第一原理测量。 PALAAS的应用将包括研究以下物质的光学特性：（1）褐色碳，这种物质是生物质阴燃燃烧时大量排放的，其光学特性基本上不为人知;（2）矿物粉尘，按质量计，它是主要的环境气溶胶，具有复杂的吸收光谱;（3）气溶胶吸收光谱与气溶胶沉积对冰雪表面吸收光谱的修正之间的关系。大气气溶胶及其辐射强迫是理解和模拟全球和区域气候变化的最大不确定因素。 在雪和冰的表面上由于表面微扰的改变，气溶胶沉积后引起额外的不确定性。 气溶胶光吸收系数的普通滤波器测量遭受大量的系统误差;气溶胶光吸收系数的单波长光声测量不足以表征具有强且未知的吸收波长依赖性的气溶胶的辐射影响（例如，棕色碳和矿物尘埃气溶胶），这可能对大气气溶胶吸收和降低气溶胶单次散射率（气溶胶辐射强迫中的一个关键量）做出非常重要的贡献。 此外，由于环境气溶胶浓度和光学在空间和时间上的不均匀性很大，因此需要光学卫星遥感对气溶胶辐射强迫进行全球、空间和时间分辨。 然而，卫星监测需要详细了解气溶胶吸收光谱。 PALAAS将利用一种新型的宽带超连续激光器，覆盖400至2000纳米的太阳光谱范围，在32个可定制的光谱波段内同时测量气溶胶光吸收和散射系数以及气溶胶单次散射系数，从而使波段数量比最先进的三波长光声仪器增加约一个数量级。 将使用棱镜脉冲压缩器实现这32个波段中的同时吸收和散射测量，以（1）在空间上分离超连续光谱，（2）使用自定义光学斩波器在单独的声学频率下调制每个光谱波段，（3）将光谱重新组合成激光束，以及（4）通过光声谐振器发送激光束。 利用光声仪器中的散射传感器测量散射系数和利用光声仪器测量吸收系数可以通过利用快速傅里叶变换（FFT）分析对调制频率进行解码来同时针对所有32个波长带实现。 该仪器将通过提供对气溶胶光吸收、散射和散射光谱的第一个真实的实时、原位、第一原理测量，对气溶胶光学、辐射强迫和卫星遥感领域产生潜在的变革性影响。由于气溶胶及其鲜为人知的光学特性造成的辐射强迫和气候变化模拟的不确定性，面对这些不确定性，预测全球和区域气候变化，制定和实施减缓战略，以及使社会相信科学预测的准确性，都更具挑战性。因此，在气候变化影响人类的背景下，上文讨论的知识价值将产生重要的更广泛的社会影响。 教育部分将涉及高中、本科、研究生和博士后学生，特别针对代表性不足的群体。 特别是，该项目将提供研究经验，为（1）高中学生通过与瓦肖县学区资优计划现有的合作伙伴关系，（2）本科生和研究生通过纳入正式班在内华达州，里诺，学生就业，高级论文，博士学位的大学。论文;（3）聘请博士后研究助理参与仪器开发。 博士后将由项目PI指导仪器开发，气溶胶光谱学和跨学科环境研究。仪器分类：将开发光声气溶胶光吸收和反照率光谱仪，以扩大气溶胶短波辐射传输领域的研究能力，并将其应用于气候变化和卫星遥感研究。