Abstract Urban form significantly impacts thermal conditions at the microscale. This research aims to understand how existing zoning regulations that prescribe urban form affect the microclimate of densely built redeveloped commercial and mixed-use urban areas. ENVI-met was used to simulate diurnal microclimatic conditions of two former indoor shopping malls in the Denver metropolitan area that were converted to walkable urban outdoor centers in the early 2000s – the 29th street Mall in Boulder, CO and Belmar in Lakewood, CO. Simulations were conducted for a typical summer day (June 29, 2015) and validated through on-site air temperature observations. To compare the impact of urban form on microclimate at both sites, four policy scenarios were developed to apply the hypothetical policy-driven morphology of one site to the other by changing building height, tree density, street direction, and a combination of the three factors. The combined scenario showed the largest differences in air temperature to the base case (up to 2.0 °C), which is in the order of magnitude of the RMSE (1.2 °C–2.4 °C). Site configuration influenced air temperature and wind speed creating hyperlocal cool and warm pockets. Mean radiant temperature (MRT) varied the most between the scenarios with differences of up to 15.0 °C due to tall buildings and increased shading. Urban form policies of Belmar contributed to more effective heat mitigation, particularly with respect to MRT. Findings from this empirical work demonstrate the importance of design guidelines and zoning to achieve desired microclimate outcomes and highlight the potential of planning policies to create climate-sensitive urban forms.

中文翻译：

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形式和设计政策对城市小气候的影响：评估城市再开发项目中的分区和设计指南选择

摘要 城市形态在微观尺度上显着影响热条件。本研究旨在了解规定城市形态的现有分区法规如何影响密集重建的商业和混合用途城市地区的小气候。ENVI-met 用于模拟丹佛大都市区的两个前室内购物中心的昼夜小气候条件，这些购物中心在 2000 年代初期被改造成适合步行的城市户外中心——位于科罗拉多州博尔德的第 29 街购物中心和位于科罗拉多州莱克伍德的贝尔马。是在一个典型的夏日（2015 年 6 月 29 日）进行的，并通过现场气温观测进行了验证。为了比较城市形态对两个地点小气候的影响，通过改变建筑物高度、树木密度、街道方向以及三个因素的组合，开发了四种政策情景，将一个地点的假设政策驱动形态应用于另一个地点。组合情景显示空气温度与基本情况的最大差异（高达 2.0 °C），其数量级为 RMSE（1.2 °C–2.4 °C）。场地配置影响了气温和风速，创造了超局部的凉爽和温暖的口袋。由于高层建筑和阴影增加，平均辐射温度 (MRT) 在不同情景之间变化最大，差异高达 15.0 °C。贝尔玛的城市形态政策有助于更有效地缓解热量，尤其是在捷运方面。