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。尽管实施了大量的排放控制措施，但将排放与空气质量联系起来的复杂过程意味着，相当大比例（分别为80%和97%）的欧洲人口生活在颗粒物（PM）和臭氧（O3）水平超过欧盟限值和目标值的城市。据估计，这两种污染物在欧洲造成35万至20万人过早死亡。NERC的战略文件指出：“在英国，空气污染每年给人类健康造成的经济损失达150亿英镑，这还不包括对环境和农作物的损害。”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发作期间，对于为决策者和公众提供有效的预测至关重要。尤其重要的是，政策监管者要了解可以由国家政策调节的本地空气质量驱动因素，而不是来自欧洲大陆或其他地方的区域污染。城市地区尤其令人关注，因为它们不仅是区域污染的受者，而且由于人口密度高，它们的供热和公路运输产生的当地排放量也很高。它们还受到城市热岛效应的影响，这可能影响空气污染的化学性质。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控制城市地区空气质量差的关键区域和本地过程中的不确定性，无论是现在还是将来。该提案将开发一个新的模型框架，使用一套嵌套的模型来模拟从区域到城市的大气成分和天气，包括整个英国和伦敦上空的城市热岛效应。该提案将进一步利用最近ClearfLo和REPARTEE在伦敦的现场活动中最先进的NERC测量，汇集建模和测量专家，以确定高臭氧和PM事件的控制因素。基于这些野外测量，将构建一个详细的化学环境盒模型，并用于计算平均和偶然条件下O3的原位化学产量。将根据这些盒模型和现场活动结果以及广泛的网络测量来评估耦合的区域-城市模型。将使用多种方法来探测高O3事件期间区域和地方对O3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模型结果来确定。亚硝酸对城市地区O3和PM氧化化学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同时发生。在热浪期间，天气条件可能改变排放和沉积过程。将确定这些导致污染水平升高的过程的相对重要性，例如减少O3沉积。为了研究未来排放和气候变化对城市空气质量的影响，将进行高分辨率的气候化学模拟，这些模拟始终能够解释化学变化和从区域到城市尺度的运输，并评估未来对空气质量极端事件的影响。耦合模式框架和高分辨率气候预估的概念验证研究证明了预期研究的可行性。该提案包括了基础化学、大气成分和气候变化等学科的建模和测量科学家之间的强有力合作，以促进我们对现在和未来驱动区域到城市尺度空气质量过程的理解。

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.