南京夏季城市热岛时空分布特征的观测分析

Observation analysis on spatial and temporal distribution characteristics of summer urban heat island in Nanjing

摘要:

利用2010年南京夏季城市热岛三维观测试验资料，分析了南京夏季典型天气条件下城市热岛的时空分布特征。结果表明，南京夏季高温晴天日平均热岛强度达1 ℃以上，夜间热岛强度稳定且强于白天，热岛分布具有方向性特征并与城市土地利用现状对应较好。白天，城市大气混合层的发展速度和高度均大于郊区；夜间，由于城市大气层结的不稳定及下垫面的粗糙特性，致使城市低空始终存在着一个对流混合层，其高度至少有250 m。城市下垫面高热量储存和强湍流输送的共同作用形成边界层内热岛，热岛强度总体上随高度递减，影响高度在白天约900 m、夜间约300 m。

Abstract:

Using the three dimensional observation test data of urban heat island(UHI) in Nanjing in summer 2010,spatial and temporal distribution characteristics of urban heat island under typical weather conditions were analyzed.The results showed that daily mean UHI intensity on sunny days was over 1 ℃ in Nanjing in summer.UHI intensity was stronger and more stable during nighttime than that in daytime,with UHI distribution displaying directional characteristic and corresponding well to urban land-use conditions.During daytime,mixed layer in urban areas developed faster and was higher than that in the suburbs.During nighttime,there existed a long lasting convective mixed layer at low altitude in the city due to the unstable atmospheric stratification and the roughness of the underlying surface,which was as thick as more than 250 m.Owing to the storage of a large amount of heat and strong turbulent transport in urban underlying surface,heat island came into being in urban boundary layer,with UHI intensity decreasing with height.Heat island in boundary layer extended up to 900 m in daytime and maintained at 300 m at nighttime.