Impacts of Urban Expansion on the Urban Thermal Environment:A Case Study of Changchun,China

Urbanization,especially urban land expansion,has a profound influence on the urban thermal environment.Cities in Northeast China face remarkably uneven development and environmental issues,and thus it is necessary to strengthen the diagnosis of thermal environmental pressure brought by urbanization.In this study,multi remote sensing imageries and statistical approaches,involving piecewise linear regression(PLR),were used to explore urban expansion and its effects on the thermal environment of Changchun City in Jilin Province,China.Results show that Changchun experienced rapid urban expansion from 2000 to 2020,with urban built-up areas increasing from 171.77 to 525.14 km^(2).The area of the city’s urban heat island(UHI)increased dramatically,during both day and night.Using PLR,a positive linear correlation of built-up density with land surface temperature(LST)was detected,with critical breakpoints of 70%-80%during the daytime and 40%-50%at nighttime.Above the thresholds,the magnitude of LST in response to built-up density significantly increased with intensifying urbanization,especially for nighttime LST.An analysis of the relative frequency distributions(RFDs)of LST reveals that rapid urbanization resulted in a significant increase of mean LST in newly urbanized areas,but had weak effects on daytime LST change in existing urban area.Urban expansion also contributed to a constant decrease of spatial heterogeneity of LST in existing urban area,especially at daytime.However,in newly urbanized areas,the spatial heterogeneity of LST was decreased during the daytime but increased at nighttime due to urbanization.

Characteristics and Trends of Urban Waterfront Human Settlements Based on CiteSpace

Urban waterfront human settlements have gradually become a hot topic for research in recent years.Using CiteSpace,597 publications from 2017 to 2023 that were retrieved from the Web of Science were analyzed and sorted out,and the following characteristics were found:(1)The research hotspots transitioned from thermal comfort evaluation to the functional mechanism of water bodies,and then to the impact on the environment and residents’behavior.(2)The integration of disciplines has promoted the diversification of perspectives on urban waterfront human settlements,and the content has become more concentrated in interdisciplinary fields.Research on corresponding technology and methods of urban waterfront human settlement has improved,and so has the extensiveness of the experiments.(3)The research on urban waterfront human settlement from the perspective of ecology has been improving.The research focuses more on the harmonious coexistence of ecological and cultural values and human beings.

天津市中心城区典型城市形态原型中建筑形态的热环境效应

以天津市中心城区为例,使用Landsat-8遥感影像反演地表温度(LST),以表征城市热环境。同时,采用建筑数据量化17种建筑形态指标,并识别9种典型城市形态原型。在此基础上,分析不同城市形态原型间的地表温度差异,并用多元线性逐步回归方法探究不同城市形态原型中建筑形态的热环境效应。结果表明:①不同城市形态原型之间的夏季地表温度差异显著,低层高密度区地表温度均值最高,高层低密度区最低;②不同城市形态原型中建筑形态对夏季地表温度均有显著影响,但影响程度存在差异;③不同城市形态原型中各建筑形态因素对夏季地表温度影响方向一致,但重要性存在差异。因此,城市开发和更新中应关注城市形态模式和建筑形态,提出因地制宜的建筑形态调控策略。

Retrieval of urban land surface component temperature using multi-source remote-sensing data

The components of urban surface cover are diversified,and component temperature has greater physical significance and application values in the studies on urban thermal environment.Although the multi-angle retrieval algorithm of component temperature has been matured gradually,its application in the studies on urban thermal environment is restricted due to the difficulty in acquiring urban-scale multi-angle thermal infrared data.Therefore,based on the existing multi-source multi-band remote sensing data,access to appropriate urban-scale component temperature is an urgent issue to be solved in current studies on urban thermal infrared remote sensing.Then,a retrieval algorithm of urban component temperature by multi-source multi-band remote sensing data on the basis of MODIS and Landsat TM images was proposed with expectations achieved in this work,which was finally validated by the experiment on urban images of Changsha,China.The results show that：1） Mean temperatures of impervious surface components and vegetation components are the maximum and minimum,respectively,which are in accordance with the distribution laws of actual surface temperature; 2） High-accuracy retrieval results are obtained in vegetation component temperature.Moreover,through a contrast between retrieval results and measured data,it is found that the retrieval temperature of impervious surface component has the maximum deviation from measured temperature and its deviation is greater than 1 ℃,while the deviation in vegetation component temperature is relatively low at 0.5 ℃.

城市建成环境因子对热环境的影响机制研究——以天津市中心城区为例

掌握城市热环境空间异质性分布情况及其影响因素是研究热环境的关键问题,调整相关城市建成环境的参数范围或结构特征是缓解城市热环境的有效措施.本文以天津市中心城区为研究范围,分析天津市地表热环境的空间异质性分布特征,并通过数理分析探究8个城市建成环境因子对热环境的影响机制.研究结果表明:①天津市热环境整体呈斑块式分布且热核数量较多,空间分布具有较强的自相关性;②街区建成环境因子中,开放空间率、归一化植被指数、绿地率对地表热环境具有负向影响,绝对粗糙度对地表热环境具有正向影响,而建筑体形系数对地表热环境呈现出双向调节的影响作用;③不同回归模型组合方式下各建成环境因子对地表温度的综合影响程度差异显著,影响范围则随着空间尺度的增大更为广泛.根据分析结果,针对性地提出建设层面的热环境优化方法和管理层面的热环境评估建议,为同类型的城市热环境研究提供参考.

控规阶段的城区热环境评估分析软件

针对城市规划中的控制性详细规划阶段,将影响热环境的控规参数进行分类,并选用新标准有效温度、湿黑球温度、热岛强度作为热环境评估指标.在城市区域热气候预测模型的基础上,采用单因子变量的方法分析各控规参数对评估指标的影响,得到各评估指标的逐时简化计算模型,并与原计算模型进行对比验证.结果显示简化模型更为简便快速,具有较高的计算精度,并极大提高了运算速度.通过将数据导入、数据维护、图形展示、数据导出等模块与简化计算模型进行耦合,开发了城市控制性详细规划热环境评估软件,并对广州规划区域进行实例应用,得到4个测试地块的逐时热环境指标值(OUT-SET*、UHII和WBGT),并实现各参数的界面图形可视化.结果分析显示研究区域整体的OUT-SET*平均值分布在28~30.5℃,WBGT的最大值分布在29~30℃,地块1~3的UHII在0.4~1.2℃,而地块4则出现局地冷岛效应.不同地块的控规参数设置对热环境指标的分布有重要影响.

Changes of the Thermal Environment Caused by a City-Wide Lockdown:The Case of Wuhan City

The impact of the COVID-19 epidemic in Wuhan caused the city to go into a lockdown in January,2020,and most outdoor activities stopped,which provided a chance to investigate the impact of human activities on the urban thermal environment.Using the land surface temperature(LST)and population distribution data,this paper analyzes the changes between normal workdays and the lockdown period.The results show that maximum population and LST changes can be seen in industrial and commercial areas,and the LST hot spots shrink and cold spots expand in many areas during the lockdown,which identifes that the impact of the lockdown on the urban thermal environment varies according to different types of lands.However,it should be noted that the LST has a similar spatial distribution during the two periods,in spite of the signifcant changes in population size.Compared with population size,the urban morphology indicators have a higher correlation with the LST.This indicates that the urban thermal environment is dominated by urban morphology,and the infuence of human activities on it is still limited.All fndings can help urban planners to improve the existing methods to address both climate change and public health issues.

基于遥感的城市景观热环境效应研究——以重庆市主城区为例

以TM影像为数据源,采用遥感和地理信息系统技术研究了重庆市主城区不同景观表面温度的差异及其与植被指数之间的关系。研究表明,重庆市主城区存在明显的热岛效应,城市干线对热岛的空间分布具有很大影响;不同城市景观的表面温度存在显著差异;城市地表温度与植被指数具有大致相反的空间分布规律。

岛礁密集建筑群长波辐射计算模型

中国南海地区常年四季如夏,温湿度波动小,辐射热是建筑的主要热源。为了研究南海岛礁上围护结构长波散热强度及建筑围合对长波散热的影响,建立由直射分量和反射分量组成的长波辐射计算模型。该模型采用视野因子替代传统辐射计算中的角系数,采用基尔霍夫电流定律计算多个表面的反射辐射。通过多地的实测数据验证该模型的有效性,为后续建筑长波散热研究奠定基础。

Near ground air temperature calculation model based on heat transfer of vertical turbulent and horizontal air flow

In order to calculate the air temperature of the near surface layer in urban environment,the surface layer air was divided into several sections in the vertical direction,and some energy balance equations were developed for each air layer,in which the heat exchange due to vertical turbulence and horizontal air flow was taken into account.Then,the vertical temperature distribution of the surface layer air was obtained through the coupled calculation using the energy balance equations of underlying surfaces and building walls.Moreover,the measured air temperatures in a small area(with a horizontal scale of less than 500 m) and a large area(with a horizontal scale of more than 1 000 m) in Guangzhou in summer were used to validate the proposed model.The calculated results accord well with the measured ones,with a maximum relative error of 4.18%.It is thus concluded that the proposed model is a high-accuracy method to theoretically analyze the urban heat island and the thermal environment.

An Analysis of Spatio-Temporal Trends of Land Surface Temperature in the Dhaka Metropolitan Area by Applying Landsat Images

Land surface temperature (LST) is a basic determinant of the global thermal behavior of the Earth surface. LST is a vital consideration for the appraisal of gradual thermal change for urban areas to examine the strength of the thermal intensity of the surface of urban heat island (SUHI) and to see how hot the surface of the Earth would be in a particular location. In this respect, the most developed urban city like Dhaka Metropolitan Area (DMA), Bangladesh is considered for estimation of LST, and Normalized Difference Vegetation Index (NDVI) changes trend in more developed and growing developing areas. The focus of this study is to find out the critical hotspot zones for further instantaneous analysis between these two types of areas. The trends of long-term spatial and temporal LST and NDVI are estimated applying Landsat images-Landsat 5-TM and Landsat OLI_TIRS-8 for the period of 1988 to 2018 for DMA and for developed and growing developing areas during the summer season like for the month of March. The supervised classification was used to estimate the land cover categories and to generate the LST trends maps of the different percentiles of LSTs over time using the emissivity and effective at sensor brightness temperature. The study found the change in land cover patterns by different LST groups based on 50th, 75th, and 90th percentile where the maximum LST for the whole DMA went up by 2.48°C, 1.01°C, and 3.76°C for the months of March, April, and May, respectively for the period of 1988 to 2018. The highest difference in LST was found for the most recently developed area. The moderate change of LST increased in the built-up areas where LST was found more sensitive to climate change than the growing developed areas. The vegetation coverage area decreased by 6.74% in the growing, developing areas compared to the developed areas from 1988 to 2018. The findings of the study might be helpful for urban planners and researchers to take up appropriate measures to mitigate the thermal effect on urban environment.

我国三大城市群地区城市和农业用地地表热环境效应对比研究

以大中小城市协同发展为特征的城市群已成为我国城市化发展的主要形式,城市化和农业作为城市群地区最主要的土地利用活动,其气候效应是国际研究的热点。然而过去研究多关注大城市的热岛效应,对更为普遍的农业活动以及中小城市城市化的气候效应认识十分薄弱。基于MODIS地表温度数据,以自然林地为参照,提出了一种可逐像元估算土地利用地表热环境效应的新方法,进而对比分析了我国三大城市群地区(京津冀、长三角和珠三角)城市和农业用地地表热环境效应及其驱动因子差异。结果表明各城市群白天城市热岛效应明显,地级以上城市年平均热岛强度达3.2℃以上,但最强热岛均未发生在核心城市。夜晚热岛效应明显减弱,京津冀和长三角部分城市甚至出现冷岛效应。农业用地在白天亦表现出明显的增温效应,特别是在京津冀地区,而在夜晚除珠三角城市群外,降温效应明显,京津冀和长三角地区平均降温2.3℃和0.7℃。虽然城市用地平均增温强度大于农业用地,但农业用地因面积优势对区域温度变化起控制作用。白天城市和农业用地整体导致各城市群温度明显增加,京津冀增温最高(4.0℃),夜晚二者导致长三角和京津冀地区平均温度降低。研究还发现各城市群城市和农业用地地表热环境效应时空异质性极大,主要受植被、地表反照率、气候背景和人口密度控制。本文对制定缓解气候变化的土地利用策略具有重要的指导意义。

基于遥感的三亚市不透水面及热环境效应分析

城市化进程的快慢是权衡一个地区经济增长速度和社会发展水平的重要指标,改变着城市居住热环境。不透水面的分布能够很好地展现城市化的方向及趋势。三亚作为中国亚热带海岛旅游城市,近年来大量人口的涌入导致三亚城市发生了巨大变化。为了更好地了解三亚市城市化及其对城市热环境的影响,以1998、2011、2018年的Landsat 5 TM和Landsat 8 OLI/TIRS卫星遥感影像作为主要数据源,利用归一化差值不透水面指数(NDISI)对三亚市近21年来的不透水面时空变化及其对地表温度影响进行了研究。结果表明,三亚市的不透水面积在21年间净增长206.5 km2,扩大了1.58倍左右,特别是2011年以后人口和经济的快速增加,不透水面扩张速率提高了3倍以上。统计表明,不透水面与地表温度显著正相关,不透水面增加显著引起地表温度升高,而植被和水体能够显著缓解地表温度的升高,抵消不透水面对地表温度的正效应。

城市地铁运行期热环境现状分析及对策研究

我国城市地铁工程建设已进入跨越式发展阶段,但在地铁运行期,地下空间(站台、站厅)及车厢内部的热环境给使用者的舒适度带来一定影响。本研究以某市地铁X号线为研究对象,对其中6个站点的站台、站厅和5列车厢的热环境展开监测,深入分析城市地铁运行期热环境现状,并进一步提出改善地铁热环境状况的建议和措施。

环境气候研究下的河谷城市通风廊道规划探析--以洛阳市为例

日趋严重的雾霾、热岛效应逐渐成为城市发展的困扰,城市通风廊道规划引起学界的广泛关注。该文在对环境气候研究的基础上,以中原地区河谷城市洛阳为例,进行城市风、热环境模拟分析,绘制城市气候图,并提出规划建议;在此基础上将城市划分区域,构建网络状城区通风廊道系统;最后提出过程控制的管理建议以及发展展望。对河谷城市通风廊道系统规划构建,具有普遍的借鉴意义。

城市通风廊道建设背景下北京地区气候环境特征与影响分析

2020—2035年北京市通风廊道将步入精细化建设阶段,本文通过分析北京地区整体风环境数据、landsat-8卫星数据,北京全市街巷总悬浮颗粒物TSP(Total Suspended Particulate)浓度排名数据,三类气候环境数据,分析当下北京地区风环境、热环境、大气总悬浮颗粒污染物空间分布的特征;总结当下北京市面临的城市通风条件差、城市热岛效应显著、市内空气质量差异显著、局地大气污染严重等问题;阐释北京市城市通风廊道规划建设将如何解决北京气候方面的"痛点"问题,为北京地区气候环境治理及城市通风廊道进一步的精细化规划建设提供研究思路。

Governance of Urban Green Open Space for Responding to Climate Change

In the global actions to address climate change, urban open green space is one of the main spatial objects that can be used to effectively mitigate greenhouse gases and to promote the implementation of climate adaptive policies. From a global perspective, this paper firstly analyzes the governance strategies and cooperation mechanisms of urban open green space as responding to climate change in European countries. Then, taking the Central City of Beijing as a case, the paper explores its urban thermal environment, distribution of urban open green space, and climate governance operation based on the specific conditions in China. Further, with the digital technologies of GIS and RS, it analyzes the nature and related governance demands of urban open green space and then divides the Central City of Beijing into four governance zones, following which this paper discusses the climate policy strategies and implementation approaches of each governance zone.

湿热地区高层住区热环境设计参数对热岛强度的影响研究

减缓住区热岛强度是绿色建筑和生态城市建设的重要内容。以往研究从局部和整体层面对湿热地区住区气温及热岛强度展开测试和研究。本文以广州高层住区为例,在夏季晴热天气条件下开展住区现场实测。测试指标主要包括郊区、城区和住区的气温以及住区热环境设计参数。文章从城区、住区、测点三个尺度,分析探讨气温和热岛强度的变化特征以及形成机制。研究指出,以郊区气象站为基准计算住区热岛强度,因受所在城区局地热岛强度的影响,无法合理评价不同住区热环境设计的优劣,而以城区气象站为基准,可避免局地热岛的干扰,计算和评价更为合理。热环境设计参数,即天空角系数、阴影率和叶面积指数,是影响住区和测点热岛强度的关键因素。热岛强度的定义应取同一尺度或相邻尺度空间的气温差。