不同类型冷却屋顶方案对城市群热环境的缓解效果

利用耦合单层城市冠层模型的中尺度数值模式WRF/UCM,选取8组不同反照率和绿化比例的屋顶冷却方案进行敏感性试验,模拟研究不同冷却屋顶方案对长三角城市群2013年夏季城市热环境的影响,并分析其影响机制。结果表明：不同冷却屋顶方案对城市群热环境的缓解效果与屋顶参数之间呈很强的线性关系。高温热浪天气下,HR4（反照率为1.0）和GR4（屋顶绿化率为100%）方案的制冷度日数分别降低了14.7%和10.9%,节约的能源比普通夏日更多。同时,高温热浪天气会增强热岛强度,高反照率屋顶方案在白天对热岛起到更有效的缓解,热浪天气下日平均热岛强度最大可降低1.36℃。相同方案下,在高温热浪天气下的缓解效果均胜于普通夏日,平均而言,高反照率屋顶和屋顶绿化的降温效果分别增大38.5%和34.9%,增湿效果分别增大29.5%和21.9%,这主要是由于在高温热浪天气下,高反照率屋顶方案能够减少更多的净辐射通量,屋顶绿化方案能够释放更多的潜热通量。此外,城市格点密集区域的降温效果优于分散的城市区域,处于城市群中的常州区域较单独的杭州区域的降温幅度平均高32%。

Mitigation effect of different cool roof schemes on thermal environment of urban agglomeration

In this paper,a mesoscale numerical model coupled with a single-layer urban canopy model(WRF/UCM)was used to conduct sensitivity tests on eight roof cooling schemes with different albedo and greening ratio to simulate the impact of different cooling roof schemes on the urban thermal environment of Yangtze River Delta urban agglomeration in summer of 2013,and the influence mechanism was also analyzed.The results show that:there is a strong linear relationship between the mitigation effect of different cooling roof schemes on urban agglomeration thermal environment and the roof parameters,and the mitigation effect on heat-wave is better than that on normal summer under the same scheme.During heat wave,the cooling degree days of HR4(albedo of 1.0)and GR4(green fraction of 100%)are reduced by 14.7%and 10.9%,respectively,which saves more energy than normal summer.Heat-wave can enhance the intensity of heat island,and the high albedo roof scheme can reduce the heat island by 1.36℃in the daytime.On average,the cooling effect of high albedo roof and roof greening increased by 38.5%and 34.9%,respectively,and the humidification effect increased by 29.5%and 21.9%,respectively.This is mainly because the former can reduce more net radiation flux in heat wave,and the latter can release more latent heat flux in heat wave.In addition,the cooling effect of dense urban grid areas is better than that of scattered urban areas.The average cooling range of Changzhou area in urban agglomeration is 32%higher than that of Hangzhou area.