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.

气溶胶是悬浮在气体中的液体或固体颗粒，在我们的大气中无处不在。大气气溶胶的来源包括燃烧化石燃料产生的人为排放，以及海洋喷雾、沙漠灰尘和野火等生物质燃烧源产生的自然源。这些气溶胶对我们的环境有重大影响，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。事实上，大气模型中气溶胶的代表性是预测未来气候的最大不确定性之一。在全球范围内，气溶胶粒子将阳光散射回太空所产生的净气溶胶冷却效应部分抵消了温室气体的变暖影响。在区域基础上，吸收光的气溶胶，如燃烧产生的气溶胶，可以加热大气，推动大气动力学和区域气象学的变化，如云的形成。然而，气溶胶-光相互作用的量化存在很大的不确定性，这降低了我们对区域气象学和未来气候模型的信心。我们对气溶胶-光相互作用的理解的提高可能会导致在管理气候变化影响方面更有效的风险缓解策略。气溶胶光吸收特别不确定，在气候模型中表现不佳。在某种程度上，这种不确定性是由于对气溶胶吸收的观测不佳造成的，这种观测妨碍了对气溶胶光学特性的准确描述，以及这些特性如何取决于气溶胶来源、寿命和环境湿度等因素。因此，最近几年已经看到了光声光谱（PAS）技术的发展，可以部署从大气研究飞机上原位采样的气溶胶吸收。Cotterell博士与英国气象局的研究人员合作开发了定制的、国际领先的PAS仪器，这些仪器从FAAM研究飞机上部署，为大气科学界提供了对气溶胶光吸收的广泛观测。然而，与直接量化气溶胶吸收的其他技术一样，PAS测量仅限于不含任何挥发性组分（如水）的颗粒;气溶胶中挥发物的存在在光谱询问期间由蒸发效应引起的确定的吸收系数中引入了显著的偏差。事实上，有很少的知识，如何气溶胶的吸收与水的吸收在经常遇到的高湿度环境中变化，因此，吸收与湿度的变化被忽略在大气模型。因此，这是至关重要的，新技术的发展，使含挥发性particle.This项目开发的光声光谱，称为相移光声光谱（PS-PAS）的吸收观测，提供额外的相移信息在气溶胶样品的测量过程中的新的实现。通过一系列的实验室实验结合光声能量传递过程的建模，我们将证明，PS-PAS数据使测量的气溶胶吸收系数蒸发效应的校正。除了提供强有力的光吸收特性外，新的相移数据产品还将允许研究气溶胶粒子的挥发性，这是气候模型预测大气气溶胶数量浓度、尺寸分布和化学成分变化所需的一个关键特性。重要的是，这些仪器将随时可从FAAM研究飞机上部署，为英国提供新的世界领先的观测能力。大气科学家将首次拥有为下一代气候模型开发新的、准确的气溶胶吸收和挥发性描述所需的关键数据集。