Research of Index Mechanism Affecting Urban Thermal Environment

Abstract

Urban form has important influence on urban climate and thermal environment. Any essential index in urban form is more or less related to thermal environment. As pointed out above, urban thermal environment has scale characteristics. Therefore, it is particularly important to explore the influence mechanism of urban form indexes on thermal environment on different scales thus to lead thermal environment via urban form control, improve outdoor thermal comfort and reduce the energy consumption of urban buildings. Urban scale, city size, overall land layout and ventilation corridor can affect thermal environment. However, the practicality is quite low; while for neighborhood scale in the central area, urban form combination, underlying surface pattern and materials significantly affect thermal environment. The spatial form is irreversible. The underlying surface form and material can relatively be easily improved. Therefore, for urban planning, it seems very important to consider its influence on urban thermal environment before urban form planning. Simulation verification was carried out based on existing research achievements on thermal environment and urban climate. In addition, simulation of form index and thermal environment under the influence of single variable was performed as well. A total of 13 index factors including overall layout index, special form indexes and underlying surface index were selected (Fig. 2.1): ① overall layout: density/height/intensity; ② special form indexes: sky visibility factor (SVF)/height-width ratio of street/enclosure degree of street/street and building direction/enclosure coefficient/shadow coefficient/dispersion degree; ③underlying surface: vegetation coverage/impervious surface area/material and albedo. The influencing mechanism of urban land use and anthropologic heat on urban thermal environment was discussed on two aspects, namely land for temperature rising and land for temperature reduction.