The energetics of urban heat islands

城市热岛（Urban Heat Island，简称UHI）是指一个城镇或城市相对于其周边乡村的特征温度。对于一个人口约100万的城市来说，每年的城市热岛指数约为1摄氏度，但在有利的条件下，可能高达12摄氏度。这是人类对气候影响最明显的例子。UHIs看起来很简单：容易找到，测量，也许解释，并有许多实际意义的人的舒适和热应力，成本的加热或冷却的房子和长度的生长季节。它还影响空气污染物的混合和化学以及其他几种天气现象，包括湿度，雾，霜冻，当地微风，云的发展和雷暴。尽管UHI明显简单，但它们实际上是复杂的和多方面的，并且不幸的是，申请人认为还没有进行严格的研究。使用严格的新的科学协议，根据申请人的丰富经验，现有的工作将进行分析，以创建一个现代综合的城市热岛。它将澄清和量化城市热岛的真实性质，并提供一个可靠的数据库，对模型进行测试。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，其规模为街道峡谷和街区，以及与行星边界层其他部分的相互作用，该模型采用了现有的最佳物理和建模技术。它将包括所有通过辐射，传导和对流进行的热交换，建筑物周围的流动以及植被的作用。当根据观测结果进行验证时，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特性在改变城市热气候方面的作用。经过验证的模型将被用来回答有关世界任何地方的城市热岛的规模和动态的问题。这将有助于量化潜在设计解决方案的影响和价值，以减轻UHI的负面影响，并帮助设计更简单的工具，供能源和水设施，空气污染机构，卫生当局和其他人使用，以便在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.