A global perspective on the urban heat island effect

城市热岛效应的全球视角

• 批准号: 2109383
• 金额: --
• 依托单位: University of Reading
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2018
• 资助国家: 英国
• 起止时间: 2018 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2109383
• 关键词: global; perspective; urban; heat; island

The areal coverage of urban areas is expanding in many parts of the globe, with 70% of the world's population projected to live in towns and cities by 2050. The urban heat island effect can cause cities to be 6-12C warmer than the surrounding rural areas, which is of great concern due to the increased fatalities associated with heatwaves, an issue that will be exacerbated by climate change.As in many models used for global weather and climate prediction, urban areas are currently absent from the model of the European Centre for Medium-Range Weather Forecasts (ECMWF), but they are in the process of being introduced with a view to becoming operational at 9-km resolution in the next few years. This involves modification of the surface roughness and water availability, and a rigorous treatment of the turbulent and radiative exchanges at the principal elements of an urban area (the streets, walls and roofs). This PhD project is an excellent opportunity to be involved in this exciting work, from development of the underpinning science of modelling urban areas, through to the implementation and exploitation of this new capability in the ECMWF system to answer important scientific questions on a global scale.The proposed approach to the fast treatment of 3D radiative exchanges in urban areas is at the forefront of the science of radiative transfer modelling but will require several additional features to be developed and evaluated. A potential advantage will be that very few parameters will be required to describe the morphology of urban areas. An important task will be to examine existing global datasets to determine appropriate values to use for different urban forms globally.With urban areas added in on a global scale, there will be the capacity to run a fully interactive global weather forecast model. This will enable s a large number of new questions about the impact of urban areas, and the importance of cities of different sizes, to be addressed more comprehensively than has been done to date.The PhD project would have three components involving a number of key questions:1.How can we optimally represent 3D radiative transfer in urban areas? A good starting point will be a new method "SPARTACUS" that has recently been developed for efficiently representing the 3D interaction of solar and thermal-infrared radiation with randomly distributed objects and has been applied successfully to both clouds and vegetation. The studentship will address what changes will be needed to adapt it for buildings? What is the impact on radiation of incorporating trees and parks into the urban landscape? How well does this approach match benchmark calculations from much more detailed (and computationally expensive) radiation models?2.How well does the new urban treatment in the ECMWF model predict near-surface variables (e.g. air temperature and surface fluxes of heat and moisture)? A systematic evaluation will be performed against existing observations from a number of contrasting city areas from around the world, and possibly also using satellite observations of skin temperature. By re-running the global land-surface module (which is fast) of the ECMWF model, the student will investigate how improvements in the treatment of urban areas in the model can improve performance relative to observations.3.Many intriguing scientific questions could then be asked using the full model. For example, What is the impact of urban areas globally on the weather? Whether or not the impact is significant is a topic of controversy in the literature, but the student will be able to exploit existing ECMWF software tools to determine whether forecasts are improved downstream of cities. What will be the impact of future increases in urban cover and possible mitigation efforts such as building greener cities? By modifying the global maps of urban properties used by the model it'll be possible to explore how the urban heat island effect could change in future

在地球仪的许多地方，城市地区的覆盖面正在扩大，预计到2050年，世界人口的70%将生活在城镇。城市热岛效应会导致城市比周围的农村地区高6- 12摄氏度，这是一个非常令人担忧的问题，因为与热浪相关的死亡人数增加，气候变化将加剧这一问题。正如许多用于全球天气和气候预测的模型一样，欧洲中期天气预报中心（ECMWF）的模型目前没有城市地区。但这些系统正在引进过程中，以期在今后几年内以9公里分辨率投入使用。这包括改变地表粗糙度和水的可用性，以及严格处理城市地区主要元素（街道、墙壁和屋顶）的湍流和辐射交换。这个博士项目是一个很好的机会，参与这一令人兴奋的工作，从城市地区建模的基础科学的发展，通过在ECMWF系统中实施和利用这一新的能力来回答全球范围内的重要科学问题，所提出的快速处理城市地区三维辐射交换的方法处于辐射传输模拟科学的前沿但是需要开发和评估几个附加特征。一个潜在的优势是，描述城市地区形态所需的参数很少。一项重要的任务将是审查现有的全球数据集，以确定适用于全球不同城市形态的适当数值。随着全球范围内城市地区的加入，将有能力运行一个完全互动的全球天气预报模型。这将使大量的新问题的影响，城市地区，不同规模的城市的重要性，要解决更全面比已经做了迄今为止。博士项目将有三个组成部分，涉及一些关键问题：1.我们如何才能最佳地表示三维辐射传输在城市地区？一个良好的起点将是最近开发的一种新方法“SPARTACUS”，用于有效地表示太阳和热红外辐射与随机分布的物体的三维相互作用，并已成功地应用于云和植被。学生奖学金将解决什么样的变化将需要适应它的建筑？将树木和公园纳入城市景观对辐射有什么影响？这种方法与更详细（计算成本更高）的辐射模型的基准计算结果的匹配程度如何？2. ECMWF模式中新的城市处理方法对近地表变量（如空气温度和地表热量和水分通量）的预测效果如何？将根据世界各地一些对比鲜明的城市地区的现有观测结果进行系统评价，并可能利用卫星对表面温度的观测结果。通过重新运行ECMWF模式的全球陆地表面模块（速度很快），学生将研究如何改进模式中城市地区的处理，以提高相对于观测的性能。例如，全球城市地区对天气的影响是什么？影响是否显著是文献中有争议的话题，但学生将能够利用现有的ECMWF软件工具来确定预测是否改善了城市的下游。未来城市覆盖率的增加和可能的减缓努力（如建设更绿色的城市）将产生什么影响？通过修改模型使用的城市属性的全球地图，可以探索城市热岛效应在未来如何变化