基于ENVI-met的小尺度空间优化对近地表O3生成的影响

Influence of Spatial Optimization on Near-Surface O3 Production in Small-Scale Areas Based on ENVI-met

  • 摘要: 为研究城市下垫面空间优化对区域臭氧(O3)生成的影响,以北京市东四监测子站2023年数据为基础,选取近地表气温、风环境、相对湿度等气象因子,构建O3生成气象指数(OPMCI),采用ENVI-met模拟4种情景的小尺度空间近地表气象条件,其中,基准情景为实际下垫面情况,情景1较基准情景增加了硬化地面,情景2优化了建筑高度与朝向,情景3增加了城市空间绿化。结果表明:①北京市东四监测子站O3日最大8 h平均浓度(O3-8 h浓度)与气温和太阳短波辐射均呈显著正相关(R均大于0.7),与相对湿度和风速均呈负相关,但相关性不高。②增加城市绿化可实现近地表降温、增湿和遮挡太阳直射辐射,OPMCI整体可下降0.12,从而减缓O3生成。调整建筑高度和布局可影响近地表风环境,改变O3扩散条件,但风向和风速有明显的分布差异性,对O3浓度影响复杂。大面积连片的砖石或沥青等硬化地面可加剧城市低湿环境产生,进一步促进O3生成。③大气污染溯源应结合近地表空间微气候环境特点,判断O3生成及扩散是否存在不利因素。研究显示,城市下垫面条件是影响近地表O3生成的因素之一,优化城市空间可调节微气候环境,减缓近地表O3生成。未来应尽量避免出现大面积连片式城市集中建设区,以免促进近地表O3生成。可借力“双碳”目标,推进旧城建筑改造立体绿化、增加绿色空间,逐步实现城市下垫面更新,减少促进近地表O3生成的前提条件。

     

    Abstract: To understand the effects of urban surface spatial optimization on the production of ozone (O3), meteorological factors such as near-surface air temperature, wind environment, and relative humidity were selected to establish an Ozone Production Meteorological Condition Index (OPMCI). Using the data from Beijing Dongsi Monitoring Station in 2023, ENVI-met simulation was performed to simulate the near-surface meteorological conditions under four different scenarios. The baseline scenario reflected actual near-surface conditions. Scenario 1 incorporated increased impervious surfaces compared to the baseline, Scenario 2 optimized building height and orientation, and Scenario 3 enhanced urban greening spaces. The results showed that: (1) O3-8 h at Beijing Dongsi Monitoring Station exhibited strong positive correlations with temperature and shortwave solar radiation (R>0.7), and weak negative correlations with relative humidity and wind velocity. (2) Increasing urban greening reduced surface temperature, enhanced humidity, and mitigated direct solar radiation, resulting in a 0.12 decrease in the OPMCI and O3 production. Adjusting building heights and layouts altered wind dynamics, affecting O3 dispersion. However, variations in wind direction and speed introduced complexity to the effects on O3 concentrations. Widespread impervious surfaces, such as brick or asphalt, amplified arid conditions that are conducive to O3 production. (3) Source apportionment of atmospheric pollution should consider the microclimatic characteristics near the surface to assess the detrimental factors for O3 production and dispersion. This study shows that urban surface conditions are one of the factors influencing near surface O3 production, and optimizing urban spatial configuration can regulate the microclimate environment and reduce near surface O3 production. Future urban development should avoid large, contiguous construction zones to prevent O3 production. Leveraging the ‘carbon peak and carbon neutrality’ goals to promote the vertical greening of old city buildings and expand green spaces could facilitate urban surface revitalization and reduce the preconditions that promote O3 production at the surface level.

     

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