杭州公园绿地冷岛效应及其主要影响因素

Cold Island Effect of Park Green Space and Its Influencing Factors in Hangzhou

过快推进城镇化是加剧城市热岛效应的重要原因。研究表明,城市公园绿地对缓解城市热环境具有重要作用。利用Landsat8遥感数据,通过辐射传输方程法反演杭州市研究区地表温度,从公园景观构成角度量化研究公园降温效应的主要影响因素,并进一步分析公园冷岛强度的方向性,得出如下结论。1)公园冷岛效应由多个因素共同影响。公园内部地表温度随着公园面积、水体面积和绿地面积的增大而降低;水体面积20hm^(2)以上、绿地面积30hm^(2)以上时,公园降温明显;拥有水体和林地的公园比仅有林地的公园降温幅度高约3℃。2)场地面积有限的情况下,可使公园水体占比达到30%以上、绿地占比20%~40%,当不透水面占比低于30%时,降温效果相对较佳。3)公园内增加水体、绿地斑块形状复杂度和不透水面分离度可有效降低公园内部温度。4)公园冷岛强度方向受水体面积和水体长轴方向影响较大。所得结论对城市公园空间结构的合理规划具有一定的指导意义,可为相似城市缓解热岛效应提供科学理论支撑。

Excessive urbanization is an important reason for aggravating the urban heat island effect.Studies have shown that urban parks and green spaces play an important role in alleviating the urban thermal environment.With Landsat8 remote sensing data,the surface temperature in Hangzhou study area was inverted by radiative transfer equation method.From the perspective of park landscape composition,the main influencing factors of the park’s cooling effect are quantitatively studied,and the directionality of the park’s cold island intensity is further analyzed.The results show that:1)The cold island effect in gardens is influenced by several factors.The surface temperature in the park decreases with the increase of park area,water body area and green space area;when the area of water body is more than 20hm^(2)and the area of green space is more than 30hm^(2),the park is obviously cooled.The park with a combination of water and woodland has a cooling rate of about 3℃better than that of the park without water.2)Under the condition of limited site,the proportion of water body in the park should better be more than 30%,the proportion of green space be between 20%and 40%,and the proportion of impervious surface be less than 30%,which makes the cooling effect relatively better.3)Increasing the complexity of the shape of water bodies,green patches and the degree of separation of impervious surfaces in the park can effectively reduce the internal temperature of the park.4)The intensity direction of the cold island in the park is greatly affected by the water body area and the long axis direction of the water.The obtained conclusions have certain guiding significance for the rational planning of the spatial structure of urban parks,and provide scientific theoretical support for mitigating the heat island effect in similar cities.