Redai dili (Jun 2023)
Measurement and Optimization of the Urban Thermal Environment from the Perspective of Planning Control Elements: A Case Study of the Guangzhou Central Area
Abstract
The urban thermal environment problem, represented by the urban heat island effect, has recently attracted increasing attention. However, planning practitioners lack a method to fine-tune the control and management of urban thermal environments. An accurate, rapid, and quantitative urban heat island intensity (UHII) assessment tool is required that is fully integrated into the early planning process. Commonly used remote sensing and computational fluid dynamics methods have temporal and spatial limitations in the rapid and accurate quantitative evaluation and optimization of the urban thermal environment at the early stages of planning. In contrast, simplified numerical simulation methods are better choices considering computational cost and efficiency. In this study, the association between planning control elements and the urban thermal environment was determined, and the spatiotemporal differentiation characteristics of the UHII in the central area of Guangzhou were quantitatively analyzed based on the Local Climate Zone (LCZ) classification system. UHIIs are distinct from LCZs, and the open LCZ types (LCZ 4, LCZ 5, LCZ 8) have a lower average daily UHII of 0.41 °C than the compact LCZ types (LCZ 1, LCZ2, LCZ 3). The UHIIs were affected at different levels by adjusting the urban morphological parameters. The applicability of the simplified numerical simulation method Urban Weather Generator (UWG) was validated by comparing it with the measured data in the central area of Guangzhou. The results showed that the accuracy of the method was good (R2= 0.956, RMSE = 1.10 ℃, MBE = -0.28 ℃), the calculation speed was fast, the daily cycle variation of air temperature in the study area was roughly reflected, and the UWG model was suitable for fine-grained prediction with UHII. Eleven parameters related to the planning control elements were selected for global sensitivity analysis, and the average building density and average building height related to environmental capacity and building construction were observed to be the dominant factors of UHII. Building function and occupancy were secondary factors, whereas urban design guiding elements had less influence on UHII. Hence, combining the LCZ and UWG models not only simplifies the workflow of urban practitioners while analyzing and optimizing the urban thermal environment but also broadens the potential for analyzing the thermal environment in the early planning stage. In evaluating the planning design and implementation of operations and management, the pioneering role of planning control elements in regulating the urban heat environment must be fully considered. With proper planning of land use, environmental capacity, building construction, and guiding urban design, the UHII can effectively mitigate and optimize the urban thermal environment.
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