Coupling Regional and Urban processes: Effects on Air Quality

空气污染是欧洲对人类健康影响最大的环境因素。尽管有大量的排放控制，但排放和空气质量之间的联系过程非常复杂，这意味着相当大的比例--分别占欧洲人口的80%和97%--生活在颗粒物(PM)和臭氧(O3)水平超过欧盟限值和目标值的城市。据估计，这两种污染物在整个欧洲造成了35万至20万人过早死亡。NERC的战略文件指出：“在英国，空气污染每年给经济造成150亿GB的人类健康损失，这还不包括对我们的环境和农作物造成的损害。”了解在相关空间尺度上驱动空气质量的关键过程，特别是在污染超标和时段期间，对于为政策制定者和公众提供有效预测至关重要。对于政策监管机构来说，了解可以由国家政策监管的当地空气质量的驱动因素，以及来自欧洲大陆或其他地方的区域污染的贡献，这一点尤为重要。城市地区尤其令人关切，因为它们既是区域污染的接受者，又与人口密度高相关的供暖和道路运输产生的高当地排放量。它们还受到城市热岛效应的影响，这可能会影响空气污染的化学成分。我们的总体目标是使用最先进的模型和测量来量化和减少目前和未来控制城市地区糟糕空气质量的关键区域和本地过程中的不确定性。这项提议将开发一个新的模型框架，使用一套嵌套的模型来桥接从区域到城市的尺度，以模拟整个英国和伦敦的大气成分和天气，包括城市热岛效应。该提案将进一步利用最近伦敦ClearfLo和REPATITE现场活动中最先进的NERC测量结果，将建模和测量专家聚集在一起，以确定高臭氧和PM事件的控制因素。基于这些现场测量，将建立一个详细的化学环境的盒子模型，并用于计算在平均和幕间条件下的臭氧的现场化学产生。将根据这些盒子模式和实地运动结果以及广泛的网络测量对区域与城市耦合模式进行评估。将使用多种方法来探讨高臭氧事件期间区域和局地对臭氧的贡献。驱动PM事件的关键过程也将使用特定的现场测量和耦合的模式结果来确定。亚硝酸在城市地区臭氧和颗粒物氧化化学中的作用是一个关键的不确定性，将被量化。英国的空气污染事件通常与停滞事件有关，而在夏季，停滞事件可能与热浪重合。在热浪期间，天气条件可能会改变排放和沉积过程。将确定这些过程的相对重要性，例如减少臭氧沉积，从而导致污染水平上升。为了调查未来排放和气候变化对城市空气质量的影响，将进行高分辨率气候化学模拟，持续考虑从区域到城市尺度上的化学和交通变化，并评估未来对空气质量极端情况的影响。利用耦合模式框架和高分辨率气候预测进行的概念验证研究证明了预期研究的可行性。这一建议包括基础化学、大气成分和气候变化等学科的建模和测量科学家之间的密切合作，以促进我们对现在和未来推动区域到城市规模空气质量的过程的理解。

Air pollution is the environmental factor with the greatest impact on human health in Europe. Despite substantial emission controls, the complexities of the processes linking emissions and air quality, means that substantial proportions - 80% and 97%, respectively, of the population in Europe lives in cities with levels of particulate matter (PM) and ozone (O3) exceeding EU limit and target values. The two pollutants are estimated to contribute 350,000 and 200,000 premature deaths across Europe. NERC's strategy document states: "In the UK, air pollution costs the economy £15 billion every year in damage to human health, not including the cost of damage to our environment and crops." Understanding the key processes driving air quality across the relevant spatial scales, especially during pollution exceedances and episodes, is essential to provide effective prediction for both policymakers and the public. It is particularly important for policy regulators to understand the drivers of local air quality that can be regulated by national policies versus the contribution from regional pollution transported from mainland Europe or elsewhere. Urban areas are of particular concern since as well as being receptors of regional pollution, they have high local emissions from heating and road transport associated with their high population densities. They are also subject to an urban heat island effect which can impact on the chemistry of air pollution. Our overall aim is to use state-of-the-art modelling and measurements to quantify and reduce uncertainties in the key regional and local processes that control poor air quality in urban areas, both for present-day and in the future.This proposal will develop a novel model framework using a nested suite of models to bridge scales from regional to urban for simulating atmospheric composition and weather including urban heat island effects across the UK and over London. The proposal will further exploit state-of-the-art NERC measurements from recent ClearfLo and REPARTEE field campaigns in London bringing together modelling and measurements experts to determine controlling factors of high O3 and PM events. A detailed box model of the chemical environment based on these field measurements will be constructed, and used to calculate in situ chemical production of O3 during both average and episodic conditions. The coupled regional to urban model will be evaluated against these box model and field campaign results as well as extensive network measurements. Multiple approaches will be used to probe the regional and local contributions to O3 during high O3 events. The key processes driving PM episodes will also be determined using speciated field measurements and coupled model results. The role of nitrous acid on O3 and PM oxidation chemistry in urban areas is a key uncertainty that will be quantified. Air pollution events in the UK are usually associated with stagnation events, which in summer may be coincident with heatwaves. During heatwaves weather conditions may alter emission and deposition processes. The relative importance of these processes, such as reduced O3 deposition, that lead to elevated pollution levels will be established. To investigate the impact of future emissions and climate change on urban air quality, high-resolution climate-chemistry simulations that consistently account for changes in chemistry and transport from the regional to city scale will be performed and future impacts on air quality extremes evaluated. Proof of concept studies with the coupled model framework and with high-resolution climate projections demonstrate the viability of the intended research. This proposal comprises a strong collaboration between modelling and measurement scientists spanning the disciplines of fundamental chemistry, atmospheric composition, and climate change, to advance our understanding of the processes driving regional to urban-scale air quality now and in the future.