Characterization of Wind-Heat Environments in Megacities with Different Subsurface Based on Local Climate Zoning
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Abstract:
In order to clarify the heterogeneous characteristics of urban wind and thermal environments of different subsurface types, this paper analyses the characteristic differences of different subsurfaces on the local wind field and air temperature of urban blocks based on the method named Local Climate Zone by using the miniature intelligent meteorological station in Haidian District, Beijing, and the wind profile radar high-altitude wind observation data in the same region. The results show that: (1) The average wind speed of the six types of sites decreases with the increase of the roughness of the subsurface. The urban sites integrate urban buildings, green areas, water bodies and other environments to buffer sudden changes in local wind speeds compared to the sites adjacent to mountains. The larger the ratio of building footprints around the site, the smaller the sky openness, and the higher the ratio of impervious surfaces, the more significant the blocking effect of the environment on low-level wind speeds over the site. The wind speed obstruction effect is significant and the intensity of obstruction is highest for the LCZ 3. Low building density or building distribution parallel to the prevailing wind direction contributes to low-level winds. (2) During the daytime in all seasons, the temperature of LCZ 3 and LCZ 2 is higher, which highlights the influence of the local heat island effect on the increase of temperature; the average temperature of LCZ 4 near the water environment has a significant temperature increase effect during the nighttime in the spring, summer, and autumn, and the greater the area of the water body, the more significant the increase in temperature. At night in autumn and winter, the heat storage and exotherm of the impermeable subsurface of LCZ 6 exacerbate the local heat build-up and inhibit the cooling trend. Using LCZ 8 as a reference, LCZ A causes localised cooling averaging 1.5 ℃, with the largest temperature deviation of more than 2 ℃ from 19:00 to 01:00 the following day. The average daily difference in temperature is 10 ℃ in LCZ 3, highlighting the interaction between the local urban heat island warming effect and the park cold island cooling effect, with the heat island significantly stronger than the cold island during the day, and the cold island cooling dominating at night. The research results of this paper provide a research basis for subsequent mega-city planning and climate environment assessment.
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Supported by:Beijing E-Tiller Technology Development Co., Ltd.
Supported by:Beijing E-Tiller Technology Development Co., Ltd.