Light Absorption for Volatile Aerosol Particles: A New Measurement Approach

挥发性气溶胶颗粒的光吸收：一种新的测量方法

• 批准号: NE/X000036/1
• 负责人: Michael Cotterell
• 金额: $ 36.34万
• 依托单位: University of Bristol
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2023
• 资助国家: 英国
• 起止时间: 2023 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FX000036%2F1
• 关键词: Light; Absorption; Volatile; Aerosol; Particles

Aerosols are liquid or solid particles suspended in a gas and are pervasive in our atmosphere. Sources of atmospheric aerosol include anthropogenic emissions from burning of fossil fuels, and natural sources from sea spray, desert dust, and biomass burning sources such as wildfires. These aerosols have significant impacts on our environment, affecting regional air quality as well as global climate through interacting with sunlight and cloud droplets. Indeed, the representation of aerosols in atmospheric models is one of the largest uncertainties in predicting future climate. Globally, the net aerosol cooling effect provided by aerosol particles scattering sunlight back to space partially offsets the warming impact of greenhouse gases. On a regional basis, light absorbing aerosols such as those from combustion can heat the atmosphere, driving changes in atmospheric dynamics and regional meteorology such as the formation of clouds. However, large uncertainties in quantifications of aerosol-light interactions degrade the confidence we have in models of regional meteorology and of future climate. Improvements to our understanding of aerosol-light interactions could lead to more effective risk mitigation strategies in managing climate change impacts.Aerosol light absorption is particularly uncertain and is represented poorly in climate models. In part, this uncertainty arises from poor observations of aerosol absorption that hamper the development of accurate descriptions of aerosol optical properties and how these depend on factors such as aerosol source, lifetime, and ambient humidity. Thus, very recent years have seen the development of photoacoustic spectroscopy (PAS) techniques that can be deployed from atmospheric research aircraft for in situ sampling of aerosol absorption. Dr Cotterell has collaborated with Met Office researchers in developing bespoke, internationally-leading PAS instruments that are deployed from the FAAM research aircraft, providing the atmospheric science community with extensive observations of aerosol light absorption. However, as with other techniques that directly quantify aerosol absorption, PAS measurements are limited to particles that do not contain any volatile components (such as water); the presence of in-aerosol volatiles introduces significant biases in determined absorption coefficients arising from evaporative effects during spectroscopic interrogation. Indeed, there is very little knowledge of how aerosol absorption varies with water uptake in the elevated humidity environments often encountered, and thus the variation in absorption with humidity is neglected in atmospheric models. Thus, it is of paramount importance that new techniques are developed that enable observations of absorption for volatile-containing particles.This project develops a new implementation of photoacoustic spectroscopy, referred to as phase shift photoacoustic spectroscopy (PS-PAS), that provides additional phase shift information during measurements on aerosol samples. Through a series of laboratory experiments in combination with modelling of photoacoustic energy transfer processes, we will demonstrate that PS-PAS data enable the correction of measured aerosol absorption coefficients for evaporative effects. In addition to providing robust characterisations of light absorption, the new phase shift data products will allow studies of aerosol particle volatility, a key property needed in climate models to predict the evolving number concentration, size distribution, and chemical composition for atmospheric aerosols. Importantly, these instruments will be readily available for deployment from the FAAM research aircraft, providing the UK with new, world leading observational capability. For the first time, atmospheric scientists will have the critical data sets required for developing new and accurate descriptions of aerosol absorption, as well as volatility, for the next generation of climate models.

气溶胶是液体或固体颗粒悬浮在气体中，在我们的大气中普遍存在。大气气溶胶的来源包括燃烧化石燃料的人为排放，以及海上喷雾，沙漠灰尘和生物质燃烧来源（例如野火）的天然来源。这些气溶胶对我们的环境产生了重大影响，通过与阳光和云滴相互作用，影响区域空气质量以及全球气候。实际上，气溶胶在大气模型中的表示是预测未来气候的最大不确定性之一。在全球范围内，气溶胶颗粒提供的净气溶胶冷却效果将阳光散射回空间，部分抵消了温室气体的变暖影响。在区域基础上，吸收气溶胶（例如燃烧的气雾剂）可以加热大气，推动大气动力学和区域气象的变化，例如云的形成。然而，对气雾光相互作用的量化量化的很大不确定性降低了我们对区域气象学模型和未来气候的信心。改善我们对气雾光相互作用的理解可能会导致更有效的降低风险策略来管理气候变化影响。Aerosol的光吸收尤为不确定，并且在气候模型中的代表性很差。在某种程度上，这种不确定性是由于对气溶胶吸收的观察到不良的观察结果，从而阻碍了气溶胶光学特性的准确描述以及这些因素如何依赖于诸如气溶胶源，寿命和环境湿度等因素。因此，近年来已经看到了可以从大气研究飞机部署的光声学光谱（PAS）技术的发展，以原位采样气溶胶吸收。 Cotterell博士与Met Office研究人员合作开发了从FAAM研究飞机部署的定制，国际领先的PAS仪器，为大气科学界提供了广泛的气溶胶光吸收。但是，与直接量化气溶胶吸收的其他技术一样，PAS的测量仅限于不包含任何挥发性成分（例如水）的颗粒。摩塞溶性挥发物的存在引入了确定的吸收系数的显着偏见，这在光谱询问期间是由蒸发效应引起的。实际上，在经常遇到的湿度升高环境中气溶胶吸收如何随水吸收而变化的知识很少，因此在大气模型中忽略了吸收湿度的变化。因此，最重要的是，开发了新技术，可以使人们可以观察到含挥发性的颗粒的吸收。本项目开发了光声光谱的新实现，即相变光声光谱（PS-PAS），可在播放气溶胶样品上测量的其他相位移位信息。通过一系列实验室实验，结合了光声能量传递过程的建模，我们将证明PS-PAS数据能够校正测得的气溶胶吸收系数以蒸发效应。除了提供光吸收的强大特征外，新的相移数据产品还将允许研究气溶胶颗粒波动率，这是气候模型中所需的关键特性，以预测大气气溶胶的不断发展的数量浓度，尺寸分布和化学成分。重要的是，这些仪器将很容易从FAAM研究飞机上部署，从而为英国提供了新的，全球领先的观察能力。对于下一代气候模型，大气科学家首次将拥有开发新的和准确描述的气溶胶吸收以及波动性所需的关键数据集。