基于遥感的银川市建成区城市扩展及其热环境变化分析

为研究银川市城市建成区扩展对热环境的影响，基于 1989、1999、2010 年和 2017 年 Landsat 系列遥感数据，采用建筑用地指数（IBI）提取 4 个年份的城市建成区信息，获取了城市形态演化指 标，利用热红外波段反演不同年份的地表温度；在此基础上，分析了城市扩展和热环境变化的时空 演变特征，探讨了城市扩展和热环境之间的响应关系。结果表明：（1）1989—2017 年银川市城市建 成区扩展面积达 506.13 km²，各时期的扩展速度和扩展强度差异明显，城市扩展具有“缓慢—快速 —稳步”的阶段性特征，城市空间形态趋于紧凑化，向着稳定状态发展，城市整体向东部和北部扩 展，重心整体向东北方向迁移约 5.54 km。（2）热岛范围随着城市扩展不断扩大，较高温区域所占热 岛比例呈先减小后增加的趋势，高温和特高温占比表现出先增加后减小的特征，热岛强度逐渐向 较高温区转移，城市热岛效应得到缓解；热岛空间分布显示，热岛逐渐由兴庆区老城区蔓延至贺兰 县和西夏区，且兴庆区热岛逐渐演化为相互独立的小次级热岛，强度有所降低；28 a 间银川市城市 热岛比例指数（URI）表现出先上升后下降的特征，整体呈上升趋势。（3）热岛区域在空间分布和扩 展方向上与城市扩展具有较高的一致性，城镇用地、公交建设用地和裸地能促进地表温度升高，而 草地和水体能够降低地表温度，公园绿地和水体能有效缓解银川市城市热岛效应且后者对降低城 市地表温度的效果要好于前者。

Urban built-up area expansion and thermal environment variation in Yinchuan City based on remote sensing

Since its establishment as the capital of the Ningxia Hui Autonomous Region, the city of Yinchuan has been facing an increasingly serious urban-heat-island effect due to rapid urbanization. To provide insight into the city’s changes, thermal environment variation, and the response relationship of urban built-up area expansion and the thermal environment in Yinchuan during the past 28 years, this study used Landsat 5 TM and Landsat 8 OLI im? age data for 1989, 1999, 2010, and 2017 to extract urban built-up area using the index-based built-up index, and the expansion intensity, speed, compactness index, fractal dimension, and center of gravity from urban morphology evolution indices such as AGR, AGA, BCI for the same period. The study also used land surface temperature (LST) values retrieved through the thermal infrared bands based on a radiative transfer equation, and calculated the ur? ban-heat-island ratio index (URI) for these four years through normalized LST. Lastly, the space-time evolution of urban built-up area expansion and thermal environment variation were studied and their response relationship was discussed. The results showed the following: (1) During 1989-2017, urban built-up area expanded rapidly, increas? ing by nearly 506.13 km2. The expansion intensity and speed of different periods varied greatly; however, they pre? sented periodical characteristics with slow-rapid-steady expansion phases. The compactness index showed an up? ward trend while the fractal dimension showed a downward trend overall, which demonstrated that the urban spatial form tended to be compact and stable. The city expanded to the east and north and the city’s center of gravity shift? ed nearly 5.54 km to the northeast. (2) The heat island area gradually increased with urban expansion, with areas of higher temperature, high temperature, and extremely high temperature increasing by factors of approximately 9, 10, and 4 over the past 28 years, respectively. However, the heat intensity transferred from the region of high tempera? ture and extremely high temperature to the higher temperature region, thus relieving the heat island effect. The heat island’s spatial distribution showed that it spread from the old town area of Xingqing district to Helan County and Xixia district. Meanwhile, the Xingqing district heat island gradually evolved into an independent small secondary island, alleviating the intense overall heat island effect of Yinchuan, and URI showed an increasing trend first and then a decreasing trend but an overall increase. (3) The spatial distribution and expansion direction of the high tem? perature region of the LST is highly consistent with urban expansion. In addition, urban land, buildings, and bare land could increase LST, whereas grass land and water could decrease it, meaning that urban green spaces and wa? ter were able to effectively alleviate the heat island effect, with water demonstrating greater LST decreases than ur? ban green spaces.