城市模型反射率测量方法与运用

介绍了一种测试城市模型反射率的试验方法。制作10个条形和十字形的城市模型进行测试,观测路面不同反射率对城市反射率的影响,并将实测模型反射率与ASTM E1918-06规范计算结果进行对比。研究发现:瞬时太阳辐射强度变化值在规范允许范围内,模型计算的反射率与ASTM E1918-06测量值的误差在0~0.1之间。当峡谷纵横比(建筑物高度与路面宽度之比)为1.0时,路面反射率从0.15提高到0.65,城市峡谷反射率增幅在0~0.30之间;提高路面反射率并不能有效提高城市峡谷反射率,尤其是纵横比较大的深峡谷。城市峡谷中的多重反射抑制城市反射率的提高。同时,反射路面将给行人增加额外的辐射通量,可能带来热不适感和眩光刺眼等问题。因此,应谨慎看待反射路面作为一个缓解城市热岛效应策略。

Approach and procedure of measuring the albedo of urban prototype

A new method of measuring the albedo of urban prototype is proposed. The method is used to measure ten urban prototypes with different pavement reflectivity and with south-north orientation, west-east orientation and cross-street orientation, respectively. The results are compared with those obtained by the ASTM E1918-06 and the modified ASTM E1918-06. It is found that when the variation of the incident solar intensity is less than 20 W/m²(a tolerant error stated by ASTM E1918A), the ASTM E1918-06 can either underestimate or overestimate the albedo of the urban canyon prototype up to 0.10. For an urban canyon(UC) with an aspect ratio of 1.0, an change from 0.15 to 0.65 of pavement albedo would cause an increase of the albedo of the UC from about 0.15 to 0.35 if the albedo of the roof and wall is about 0.40. Raising the albedo of the pavement in a UC is not an effective way to increase the albedo of the urban area, especially for UC with great aspect ratio. For low aspect ratio UC, raising the albedo of the pavement or of the parking lot introduces a sizable additional diffuse reflected radiation to the pedestrians. Therefore, it should be cautious to developing reflective pavements as an urban cooling strategy.