土地利用变化对京津冀热环境时空演变的影响

Impact of land use change on the spatiotemporal evolution of the regional thermal environment in the Beijing-Tianjin-Hebei urban agglomeration

选取中国三大城市群之一的京津冀城市群作为研究区,利用Getis-Ord Gi*指数、贡献指数等分析方法,探究了2001~2020年不同土地利用类型对京津冀城市群夏季昼夜区域热环境的影响.结果发现,夏季昼夜相对地表温度空间分布差异较大.白天,西北部和东南部的相对地表温度都较高.夜晚,西北部以冷点为主,而热点主要聚集于东南部.京津冀城市群主要以耕地、林地、草地和建设用地为主.耕地、建设用地主要分布于东南部,林地和草地主要位于西北部.其中,耕地面积最大,约占总体面积的45.5%.然而自2001~2020年,随着城市化的发展,耕地面积降低了5.2%,而建设用地面积增加了2.3%.土地利用在夏季昼夜的相对地表温度变化较大.水体在白天的相对地表温度基本低于0℃,对区域热环境具有明显的降温作用,在夜晚水体的相对地表温度则位于3~4℃,具有明显的增温作用.草地在白天对区域的降温作用不明显,而在夜晚的降温作用明显强于林地.本文通过研究不同土地利用类型对区域热环境的昼夜影响,将有助于理解区域热环境分布特征及影响机制,从而为区域层面的热岛缓解策略制定提供理论依据.

In this study, the Beijing-Tianjin-Hebei urban agglomeration(BTH), one of the three largest urban agglomerations in China, was selected as the study area.The effects of different land use types on the diurnal regional thermal environment of BTH in summer were investigated by using Getis-Ord Gi* index and contribution index.The results illustrated that the spatial distribution of relative land surface temperature(RLST) varied greatly between day and night in summer.The RLST was higher in the northwest and southeast of BTH during the day.At night, the northwest was dominated by cold spots, while the hot spots were mainly located in the southeast.BTH was mainly dominated by cropland, forest, grassland and built-up area.The cropland and built-up area were mainly located in the southeast, while the forest and grassland were mainly located in the northwest.The cropland was the largest,accounting for about 45.5% of the overall area.However, with the urbanization, the cropland decreased by 5.2% and the built-up area increased by 2.3%.In summer, the RLST of land use varied greatly during the day and night.The RLST of water body was below 0 ℃ during the day, which had significant cooling effect on the regional thermal environment.At night, the RLST of the water body was 3~4℃, which had significant warming effect.Grassland has no significant cooling effect in the daytime, but it was stronger than that of forest at night.Through analyzing the diurnal impact of different land use types on the regional thermal environment, this study could help to understand the distribution characteristics and impact mechanism of the regional thermal environment, thus expect to provide a theoretical basis for the formulation of mitigation strategies for regional heat islands.