2005-2016年北京中心城区热岛时空格局及影响因子多元建模

Spatio-temporal Pattern of Heat Island and Multivariate Modeling of Impact Factors of Beijing Downtown from 2005 to 2016

城市热岛效应作为城市范围的一种典型气候特征,在近年来受到了广泛的关注。了解城市热岛时空演变及形成原因对缓解城市热环境和提高人居舒适性有着重要意义。以北京市中心城区为例,首先,基于Landsat卫星2005、2010、2016年的热红外影像数据反演得到地表温度,采用均值标准差方法对地表温度进行划分得到多等级的热岛强度,分析城市热岛的空间格局和随时间的演变规律;其次,提取不透水层、植被、裸土和水体4种典型地物类型,统计不同年份下各热岛强度之间的转移信息并计算相关的热力景观格局指数;接着,依据离市中心的距离将中心城区分为30级缓冲区,统计分析每一级缓冲区内各地物类型的面积比例与热岛强度信息。最后,以各地物类型的统计数据,结合离市中心的距离,建立各影响因子与热岛强度之间的多元关系模型,综合分析地物类型和市中心的距离变化对城市热岛的影响。结果表明:北京中心城区整体热岛强度呈逐年增长的趋势,高等级热岛强度的热力斑块面积逐步扩张,热力景观类型的多样性随时间推移呈下降态势。不透水层对热岛强度的影响较大,具体表现为不透水层盖度越高,热岛强度越大;热岛强度随离市中心距离的增大逐渐降低。

Urban heat island effect has been widely concerned as a typical climatic feature of urban area in recent years. Understanding the spatio-temporal evolution and the causes of the formation of urban heat island are of great significance to ease the thermal environment of the city and improve the comfortability for human settlement. Firstly, we retrieved the land surface temperature of Beijing downtown based on Landsat thermal infrared images in 2005, 2010 and 2016. The mean-standard deviation method was used to divide the land surface temperature to obtain multi-grade heat island intensity for analyzing the evolution law and spatial pattern of urban heat island. Secondly, four typical ground feature types, impervious surface, vegetation, bare soil and water body, were extracted. Also, the transfer information of each heat intensity in different years and the relevant thermal landscape pattern indices were calculated. Then, according to the distance from the center of the city, we divided the downtown into 30 ring buffers and analyzed the area ratios of ground feature types and the information of heat island intensity in each ring buffer. Finally, based on the statistical data of each ground feature type and the distance from the downtown, the relationship between the influence factor and the heat island intensity is established. Also, the influence of the ground feature types and the change of the distance on the urban heat island is comprehensively analyzed. The results showed that the overall heat island intensity is increasing every year in Beijing downtown. The high grade of heat island intensity of the thermal patch area gradually expanded. The diversity of the thermal landscape types is decreasing with time. Impervious surface has a great impact on the heat island intensity. The strength of heat island intensity become greater with the percentage growth of impervious surface. The strength of heat island intensity decreases gradually with the increasing distance from the center of the city.