The energetics of urban heat islands

城市热岛（UHI）是一个城镇或城市相对于其周围乡村的特有温暖。对于一个约有100万人口的城市来说，每年的热岛指数约为1摄氏度，但在有利条件下可能高达12摄氏度。这是人类对气候影响最明显的例子。UHIs似乎很简单：很容易发现、测量和解释，并且对人类的舒适度和热压力、供暖或制冷房屋的成本以及生长季节的长度有许多实际影响。它还影响空气污染物的混合和化学性质，以及其他几种天气现象，包括湿度、雾、霜、局部微风、云的发展和雷暴。尽管UHIs表面上看起来很简单，但实际上它们是复杂和多方面的，不幸的是，在申请人看来，它们没有得到严格的研究。将根据申请人的丰富经验，使用严格的新的科学方案，分析现有的工作，以创建一个现代的综合城市热岛。它将澄清和量化全民保健计划的真实性质，并提供一个可靠的数据库，供模型进行检验。这项工作的主要部分将开发一个新的最先进的城市热岛数值模型，该模型以街道峡谷和社区的规模以及与其他行星边界层的相互作用为基础，结合了最好的物理和建模技术。它将包括所有通过辐射、传导和对流进行的热交换，建筑周围的流动和植被的作用。当与观测数据进行对比验证后，该模型将用于进行敏感性测试，以确定城市系统的不同物理性质在改变城市热气候方面的作用。经过验证的模型将用于回答有关世界各地热岛规模和动态的问题。这将有助于量化潜在设计解决方案的影响和价值，以减轻全民健康卫生系统的负面影响，并有助于设计更简单的工具，供能源和水务公司、空气污染机构、卫生当局和其他机构使用，以便在一个更温暖的世界中更可持续地管理城市。

The urban heat island (UHI) is the characteristic warmth of a town or city compared with its surrounding countryside. For a city of about 1 million the annual UHI is about 1 Celsius degree but under favourable conditions may be as large as 12 degrees. It is the most obvious example of human impact on climate. UHIs seem simple enough: easy to find, measure and perhaps explain and have many practical implications for human comfort and heat stress, costs of heating or cooling house and the length of the growing season. It also affects the mixing and chemistry of air pollutants and several other weather phenomena including humidity, fog, frost, local breezes, cloud development and thunderstorms. Despite the apparent simplicity of UHIs they are in fact complex and multi-faceted and unfortunately in the applicant's opinion have not been studied rigorously. Using strict new scientific protocols, based on the extensive experience of the applicant, existing work will be analyzed to create a modern synthesis of the UHI. It will clarify and quantify the true nature of the UHI and provide a reliable database against which models can be tested. The main part of the work will develop a new state-of-the-art numerical model of the UHI at the scale of street canyons and neighbourhoods plus interaction with the rest of the planetary boundary layer, that incorporates the best physics and modeling techniques available. It will include all heat exchanges by radiation, conduction and convection, flow around buildings and the role of vegetation. When verified against observations the model will be used to conduct sensitivity tests to determine the role of different physical properties of urban systems in modifying urban thermal climates. The validated model will be used to answer questions about the magnitude and dynamics of UHI anywhere in the world. This will help to quantify the effect and value of potential design solutions to mitigate negative aspects of UHIs and to aid the design of simpler tools for use by energy and water utilities, air pollution agencies, health authorities and others to more sustainably manage cities in a warmer world.