北京市区车辆热排放及其对小气候的影响

摘要

The urban heat island effect is worsening with the rapid urbanization of Beijing.Vehicle heat emissions are regarded as one of the most significant factors affecting the urban thermal environment.The intensity and scale of the impact of vehicle heat should not be ignored given the sharp increase in car ownership in recent years.Taking the region inside Beijing 5th ring road as the study area,this paper proposes a feasible method to calculate vehicle heat intensity through the data of transportation index,traffic density,road length,etc.The microclimate data were collected through field sampling at several typical sites.These temperature and humidity data were used to explore the quantitative relationship with vehicle heat intensity in the Beijing metropolis.The results show that vehicle heat intensity distributes in radial pattern in Beijing.The mean heat intensity ranges from 8.6 to 10.8 W/m2 and reaches 32.2-53.9 W/m2 inside the 3th ring road.The average vehicle heat intensity at daytime is 2-10 times the intensity at nighttime.The maximum value of vehicle heat appears in the mornings and evenings.Interestingly,the spatial pattern of vehicle heat has no significant difference between weekends and weekdays.The vehicle heat intensity at 8:00 a.m.shows a significant correlation with its temperature difference on main roads.The temperature amplification reaches 0.91 ℃/10 W/m2 at 8:00 a.m.At some points,we observe a significantly positive correlation between vehicle heat intensity and its temperature difference.We also notice a lag effect (10-20 min)of vehicle heat on temperature amplification.This study could provide useful information for the scientific planning of roads and urban landscapes.%快速城市化导致城市热岛效应不断加剧,超大城市的车辆排热是影响城市热环境的重要因素之一.以北京五环区域为研究区,通过交通指数、交通密度、道路长度等指标计算了交通道路排热强度,辨识出北京市区街道尺度上车辆排热的时空动态规律;选择典型位点对小气候特征进行流动与连续监测,构建空间与时间序列上车辆排热与小气候特征的定量关系.结果表明,交通排热强度呈现辐射状空间分布,市区平均排热强度为8.6-10.8 W/m2,三环内地区达32.2-53.9 W/m2,白天平均排热强度约为夜间的2-10倍,且早晚高峰期排热强度最大,非工作日的排热空间特征同工作日并无明显差异;主要道路的温差同08:00时的交通排热相关性最显著,温差增幅为0.91℃/10 W/m2;车辆排热与道路草地监测点的温差有显著正相关关系,温差增幅约为0.15℃/10 W/m2,且排热对其温差有约10-20分钟的滞后效应.车辆排热的时空动态研究有助于科学规划城市道路和景观,改善城市热环境.