广州3种树冠覆盖度绿地的微气候与人体舒适度研究

Microclimate and Human Comfort of Three Green Spaces with Different Canopy Coverage in Guangzhou

城市绿地能有效调节局部微气候及缓解城市热岛。研究绿地的微气候与人体舒适度可为城市绿地规划提供参考。以广州市二沙岛为例,在夏季日间对岛上3种不同树冠覆盖度绿地的风速、空气温度和相对湿度等微气候因子进行连续3天的实测,并采用热舒适度预测不满意率(predictive dissatisfaction rate,PPD),将其作为人体舒适度评价指标。结果表明,树冠覆盖度越大,越舒适,其影响因素如下。(1)空气温度,高树冠覆盖度的绿地降温作用最明显,其日均温度比低树冠覆盖度的绿地低1.38℃,其中10:00-16:00高树冠覆盖度与低树冠覆盖度绿地的温度差异达显著水平,而低树冠覆盖度的绿地在18:00时温度在三者中最低;(2)相对湿度,高树冠覆盖度的绿地增湿和保湿作用最明显,其日均相对湿度比低树冠覆盖度的绿地高5.98%,3种类型绿地全天的相对湿度差异均不显著;(3)风速,树冠覆盖度越低的绿地风速越大,高树冠覆盖度的绿地与低、中树冠覆盖度的绿地风速差异达到显著水平;(4)PPD值,其与温度和风速均呈极显著正相关,与相对湿度呈负相关。调节城市微气候功能最佳的是高树冠覆盖度型绿地,且其人体舒适度最好,适宜人们在夏季高温天气进行户外活动。

Urban green space can effectively regulate local microclimate and mitigate the urban heat island effect,and the study of the microclimate and human comfort of green space can provide reference for urban green space planning.The wind speed,air temperature,and relative humidity in three green spaces with different canopy coverage on the Ersha island,Guangzhou were measured in day time for three consecutive days in summer,and thermal comfort was adopted to evaluate human comfort by using the index of predicted percentage of dissatisfied(PPD).The results showed that the greater the canopy coverage the green spaces on the Ersha island the more comfortable the people feel.The resultant factors include air temperature,relative humidity and PPD index.For air temperature,the green space with the high canopy coverage has the most obvious cooling effect;its daily average temperature is 1.38℃lower than that of the green space with the low canopy coverage;the temperature difference between the green spaces with the high and low canopy coverage is significant from 10:00 am to 16:00 pm,and the green space with the low canopy coverage is the lowest in temperature among the three spaces at 18:00 pm.For relative humidity,the green space with the high canopy coverage has the most obvious effect of humidification and moisture retention,and its daily average relative humidity is 5.98%higher than that of the green space with the low canopy coverage.The relative humidity throughout the day are not significantly different among the three green spaces.For wind speed the lower the canopy coverage,the greater the wind speed in the green space,and the difference in wind speed between the green space with high canopy coverage and the green spaces with low and moderate canopy coverage reached a significant level.For the PPD index the PPD value is highly significantly positively correlated with temperature and wind speed,and negatively correlated with the relative humidity.Green space with high canopy coverage works the best in regulating the function of the urban microclimate,under which human comfort is optimal and hence suitable for human outdoor activities in hot summer weather.