Abstract:

The rapid urbanization process leads to changes in the urban thermal environment, which have an important impact on human health and urban sustainability. Improving the urban thermal environment through scientific planning and management is of great significance for improving urban livability. This study used the main urban area of Xi 'an as an example to analyze the changes in the urban thermal environment and its influencing factors based on the ECOSTRESS data from 2019 to 2022, with a resolution of 70 meters. The classification of local climate zone (LCZ), correlation analysis and zoning statistics were used for analysis. The study can provide a decision-making basis for scientific urban planning and management. The results show that 1) the study area was dominated by the local climate zone of building type (LCZ1-7), accounting for 72.94 % of the total area. The compact low-rise building type (LCZ2-3) was distributed within the first ring road of the city, while the open building type (LCZ4-7) was distributed between the first ring road of the city and the ring expressway. The natural type (LCZA, LCZB) and large low-rise and hard ground (LCZ7) were mainly distributed around the ring expressway. 2) During the daytime, the surface temperature was highest in the local climate zone of compact building type (LCZ3) and lowest in the water body (LCZA). At night, the surface temperature was highest in the water body (LCZA) and the lowest in the vegetation (LCZB). The surface temperature of the compact building type (LCZ1-3) was higher than that of the open building type (LCZ4-6), with the surface temperature of compact high-rise (LCZ1) being lower than compact middle-rise (LCZ2) and compact low-rise (LCZ3) during the daytime, and vice versa at night. 3) The high value area of surface temperature during the daytime was mainly located in the second ring road, primarily within the local climate area of compact building type (LCZ1-3), while the low value area of surface temperature was found in the vegetation (LCZA) and water body (LCZB) in the northeastern and southeastern parts of the study area. The high value area of surface temperature at night was mainly distributed in the water body (LCZB) in the northeast of the study area and the building type (LCZ1-6) area within the high-speed vicinity of the city, and the low value area of surface temperature was similar to that during the daytime. 4) The land surface temperature showed a significantly negative correlation with NDVI and a significantly positive correlation with population and nighttime light. According to these results, future urban planning in Xi’an should focus on open buildings and strengthen urban greening in the local climate zone of open building type (LCZ4-7). Additionally, the construction of ventilation corridors in the local climate zone of compact building type (LCZ1-3) can help improve the urban thermal environment.

Key words: land surface temperature, local climate zone, urban thermal environment, ECOSTRESS, diurnal scale, Xi’an city

摘要：

快速城市化过程引起的城市热环境变化，对人类健康和城市可持续发展产生了重要影响。通过科学规划与管理改善城市热环境对于提高城市宜居性具有重要意义。以西安市主城区为例，基于2019－2022年9期70 m分辨率的ECOSTRESS数据，结合局地气候区（Local Climate Zone，LCZ）分类，利用相关性分析及分区统计等方法，对城市热环境变化及其影响因素进行了分析，可为城市科学规划与管理提供决策依据。研究结果表明，1）研究区以建筑类型（LCZ1－7）局地气候区为主，占区域总面积的72.94%。其中紧凑型中低层建筑（LCZ2－3）局地气候区分布在城市一环路以内，开敞型建筑类型（LCZ4－7）局地气候区分布在城市一环和绕城高速之间，自然类型（LCZA，LCZB）局地气候区和大型低层和硬地面（LCZ7）局地气候区分布于绕城高速周边。2）日间，紧凑型建筑类型（LCZ3）局地气候区地表温度最高，水体（LCZA）地表温度最低；夜间，水体（LCZA）地表温度最高，植被（LCZB）地表温度最低。紧凑型建筑类型（LCZ1－3）地表温度高于开敞型建筑类型（LCZ4－6），且日间地表温度表现为紧凑型高层 (LCZ1)<紧凑型中层 (LCZ2)<紧凑型低层（LCZ3），夜间反之。3）日间，地表温度高值区主要分布于以紧凑型建筑类型（LCZ1－3）局地气候区为主的城市二环路内，地表温度低值区分布于研究区东北部、研究区东南部和二环西北部边缘区域的植被（LCZA）和水体（LCZB）局地气候区内；夜间地表温度高值区分布于研究区东北部水体（LCZB）和绕城高速内的建筑类型（LCZ1－6）区域，地表温度低值区与日间相似。4）地表温度与NDVI呈显著负相关，与人口和夜间灯光呈显著正相关。研究认为西安市未来建筑类型应多以开敞型建筑为主，并在开敞型建筑类型（LCZ4－7）局地气候区中加强城市绿化，同时，在紧凑型建筑类型（LCZ1－3）局地气候区中建设通风廊道，可起到改善城市热环境的作用。

关键词: 地表温度, 局地气候区, 城市热环境, ECOSTRESS, 日尺度, 西安市