Observational constraints on the global organic aerosol budget

全球有机气溶胶预算的观测限制

基本信息

批准号：
NE/J014257/1
负责人：
Dominick Spracklen
金额：
$ 6.61万
依托单位：
University of Leeds
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2012
资助国家：
英国
起止时间：
2012 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FJ014257%2F1
关键词：
Observational constraints global organic aerosol

项目摘要

Understanding climate change is one of the most important challenges facing science today. Atmospheric particles (aerosol) impact the Earth's climate through absorbing and scattering sunlight and through changing the properties of clouds. Aerosols from human activity (e.g., from car exhausts and industrial activity) are the dominant cooling forcing of the Earth's climate and have partly counteracted greenhouse gas warming over the industrial period. Quantifying this aerosol cooling is a critical step to making more accurate predictions of climate change.Over the past few decades substantial effort has been spent trying to better understand how aerosols impact climate. Much of this early effort focussed on sulfate which was known to be an important anthropogenic aerosol. However, in the past few years new instruments have allowed a detailed evaluation of the chemical composition of aerosol. A surprising result from these studies was the importance of organic carbon aerosol. In fact, in many places in the atmosphere it was found that organic carbon aerosol actually dominated the mass loading of fine (submicron) particles. Climate and atmospheric aerosol models have been unable to reproduce the amount of organic aerosol observed in the atmosphere with the model underprediction being greatest in polluted regions. Evidence points to the major problem with the models being in the treatment of secondary organic aerosol (SOA): that is organic aerosol that is formed in the atmosphere from gas-phase precursors. Improving our understanding of SOA and organic aerosol will be challenging because many 1000s of organic components and 10 000s reactions are involved in their formation. However, it is an essential step in improving both air quality and climate predictions. A further complication comes from radio-carbon observations that suggest that the majority of the organic carbon aerosol in the atmosphere is modern (non-fossil). The typical interpretation of this observation is that the dominant source of organic carbon aerosol is from biogenic (vegetation) sources. If this were the case it would be expected that the highest concentrations of organic carbon aerosol would be found over forests. However, observations show the opposite, with high concentrations over polluted regions and much lower concentrations over forests. It has been suggested that this apparent contradiction could be due to organic vapours from biogenic sources more efficiently converting to organic carbon aerosol in the presence of anthropogenic pollution. In a recent study we used a model and organic carbon observations to suggest that as much as 60% of global organic carbon aerosol could be formed through this enhancement mechanism. If this is true it has substantial implications for our understanding of aerosol climate forcing. In this proposal we will synthesise observations of organic carbon aerosol from a wide range of different instruments. The different instruments complement each other in the information they provide and together provide a rigorous and demanding test for the model. We will use this database to evaluate a global aerosol model and to improve the treatment of the sources of organic aerosol in the model. It will be the most comprehensive test of organic carbon aerosol in a global model to date. We will test whether there is strong evidence for a substantial enhancement of secondary organic aerosol by anthropogenic pollution. This work will greatly improve our understanding of the sources and processes controlling organic carbon aerosol and will help guide future field and laboratory measurements.

了解气候变化是当今科学面临的最重要挑战之一。大气颗粒（气溶胶）通过吸收和散射阳光来影响地球的气候，并通过改变云的特性。人类活动中的气溶胶（例如，汽车排气和工业活动）是地球气候的主要冷却强迫，并在工业时期部分抵消了温室气体的变暖。量化这种气溶胶冷却是对气候变化进行更准确预测的关键步骤。除了过去几十年的大量努力，试图更好地了解气溶胶如何影响气候。这项早期努力的大部分集中在硫酸盐上，这是一种重要的人为气溶胶。但是，在过去的几年中，新仪器允许对气溶胶的化学成分进行详细评估。这些研究的一个令人惊讶的结果是有机碳气溶胶的重要性。实际上，在大气中的许多地方发现有机碳气溶胶实际上占据了细（亚微米）颗粒的质量负荷。气候和大气气溶胶模型无法再现大气中观察到的有机气溶胶量，而在受污染区域中，预测不高度的模型最大。有证据表明，模型是处理次级有机气溶胶（SOA）的主要问题：那是来自气相前体大气中形成的有机气溶胶。提高我们对SOA和有机气溶胶的理解将是具有挑战性的，因为许多有机成分和10 000秒的反应参与了它们的形成。但是，这是改善空气质量和气候预测的重要步骤。另一种并发症来自无线电碳观察结果，表明大气中的大多数有机碳气溶胶是现代的（非化石）。该观察结果的典型解释是有机碳气溶胶的主要来源来自生物（植被）来源。如果是这种情况，预计在森林中会发现最高浓度的有机碳气溶胶。但是，观察结果表明相反，污染区域高浓度高，森林的浓度较低。已经提出，这种明显的矛盾可能是由于生物源的有机蒸气在存在人为污染的情况下更有效地转化为有机碳气溶胶。在最近的一项研究中，我们使用了模型和有机碳观察结果，暗示可以通过这种增强机制形成多达60％的全球有机碳气溶胶。如果这是真的，它对我们对气溶胶气候强迫的理解具有重要意义。在此提案中，我们将综合各种不同仪器的有机碳气溶胶观察。不同的工具在他们提供的信息中相互补充，并共同为模型提供了严格且要求的测试。我们将使用此数据库评估全局气溶胶模型，并改善该模型中有机气溶胶来源的处理。迄今为止，这将是对全球模型中有机碳气溶胶的最全面测试。我们将测试是否有大量证据表明，通过人为污染对二次有机气溶胶大大增强。这项工作将大大提高我们对控制有机碳气溶胶的来源和过程的理解，并将有助于指导未来的现场和实验室测量。