The role of local land-use on the urban heat island effect of Tel Aviv as assessed from satellite remote sensing

Climate change in cities has received much focus in the past few decades. Heat stress in urban areas has an adverse effect on human health and is expected to worsen in the future due to the global warming. Vegetation has been shown to mitigate this effect, but introducing ‘green’ areas into the metropolitan space is a challenging task. We assessed the thermal load in terms of surface temperature in Tel Aviv, the biggest metropolitan area of Israel. The thermal effect of four different urban land uses was estimated. Specifically, we compared the cooling effect of residential areas with high vegetation cover (referred here as ‘green’ residential) to that of small to medium size (2–40 ha) public parks. To this end, we used satellite data of land surface temperature (LST) and the Normalized Difference Vegetation Index (NDVI), as a surrogate for vegetation cover. High-temporal data were combined with high spatial resolutions data to produce 10-year average LST and NDVI maps at high spatial resolution over Tel Aviv. As expected, industrial areas had the highest LST due to lowest ratio of vegetation to free space area (1%), while ‘green’ areas displayed the lowest LST. Green residential and small-medium public parks had comparable thermal loads, with green residential having slightly lower LST (by 0.5 °C). In general, small-medium public parks displayed higher LST than expected. Inefficient use of free spaces for vegetation, i.e., relatively low vegetation cover to free space ratio, was probably the main cause for this. Public parks had a higher local cooling effect, but a less continuous one on the proximate surrounding (30–90 m from the park), probably due to their relative location in the urban fabric. Our results suggest that ‘greening’ areas within the private urban space should be encouraged at the expense of building new small-medium parks in metropolitan areas that lack the sufficient free space for larger parks. The outcome of this study may have key implications for urban planners seeking to mitigate urban heat island effects under the limitation of existing dense urban layout.     

哈尔滨市道路系统与城市热岛关系研究

采用哈尔滨市1989,2001,2007年Landsat TM遥感影像资料,利用单窗算法对地面温度进行反演,分析哈尔滨市热场的分布情况,并与20世纪90年代地形图结合来分析道路系统间的温度情况及其与城市热岛的关系。结果表明:铁路和公路温度差异显著且处于不同温度区的铁路温度也有显著的差异;铁路沿线地区热岛效应比较显著,铁路能使周围一定区域温度升高;公路系统作为一种特殊的廊道系统,对城市热岛有一定的阻隔、减缓作用;哈尔滨市铁路对热岛的影响范围不超过300 m,公路对城市热岛的降温作用最大值不超过0.4℃,在120 m以外降低作用很小或没有;绿化率的不同也影响道路对城市热岛的作用效果。     

Combined vegetation volume and “greenness” affect urban air temperature

Cities are often substantially warmer than their surrounding rural areas. This ‘urban heat island effect’ can negatively affect the health of urban residents, increase energy usage, and alter ecological processes. While the effect of land use and land cover on urban heat islands has been extensively studied, little is known about the role of vegetation volume or built-area volume about this phenomenon. We ask whether the 3-dimensional structure of urban landscapes influences variations in temperature across a city. Using heights-above-ground information derived from LiDAR data and the Normalized Difference Vegetation Index (NDVI) calculated from multispectral (4 band: Blue, Green, Red, and Near Infrared) aerial images, we estimated vegetation volume and built-area volume (non-vegetated) in Chicago, Illinois (USA). Daily minimum temperature data were obtained from 36 weather stations for summer 2011. The differences in urban air temperature across the study area were as large as 3 °C. Maximum likelihood models indicated that a combination of NDVI and vegetation volume best predicted nighttime temperature in Chicago, and that vegetation growing within 250–500 m of the weather station was most influential. Our results indicate that vegetation in “the matrix”, i.e. the area outside parks and preserves, is important in temperature mitigation since the majority of the vegetation volume in the study area occurs within residential, commercial/industrial, and institutional land uses. However, open space, which covers only 15% of the study area, has nearly as much total vegetation volume as residential land, which covers 61% of the study area. Clearly, both large wooded parks within a city and large trees scattered across residential areas are needed to best mitigate the urban heat island effect.     

半干旱区典型工业城市热岛时空分布及演变特征——以包头市为例

基于2000 年、2008 年和2015 年landsat5 TM影像和Landsat8 OLI影像,以单窗算法反演地表温度,研究包头市区近15 a 的城市热岛时空分布及演变特征,并对下垫面土地利用/覆盖类型、 NDVI 与城市热岛的关系进行了定量分析。研究结论表明：包头城市热岛15 a 来呈逐步扩展趋势,且主要集中于裸地区、工矿区、商业和人口密集区三类区域,空间演变趋势与城市扩张格局呈现出高度的一致性;城市热岛效应强度增强,但2008-2015 年以来,市中心区高温区面积比重大大降低;下垫面土地利用/覆盖类型是影响城市热岛空间分布的重要因子,地表温度呈现出裸地>工矿用地>建设用地>城市绿地>农用地>水体的规律;地表温度与 NDVI 呈现显著的负相关关系,即植被指数越高,城市的地表温度越低。     

The Spatial Structure of Land Use from 1970–2000 in the Phoenix,Arizona, Metropolitan Area

This article explores the dimensions of rapid urbanization in the Phoenix Standard Metropolitan Statistical Area (SMSA) over the past thirty years with respect to land use change. We devote primary attention to developing an understanding of what land transformations took place, the extent to which they occurred, and where they occurred. Our findings indicate that 32 percent of the Phoenix SMSA changed between 1970 and 2000. More than half of the overall change was from agriculture to some form of urban land use, and although a large percentage of the region remains open desert the parcels of desert are increasingly fragmented. This has significant implications for urban ecology and biodiversity. The growth indicates that rather than a pattern that reflects the agglomeration effects of a polycentric metropolis, the central business district of the City of Phoenix dominates the region. This has implications with respect to employment patterns, traffic congestion, and urban air quality and climate.     

珠三角地区地表温度与土地利用类型关系

随着城市化进程的加快,城市气候与环境问题日益显现,尤以城市热岛效应最为突出。通过监督分类方法对TM遥感影像进行了土地利用分类,并运用TM热红外波段线性拟合模型进行近地表气温反演,分析城市热岛的空间分布及地域性差异,以及与土地利用类型的关系。结果表明:珠三角地区近地表气温与土地利用类型紧密相关,城市建设区形成高温中心,是热岛的主要贡献因子,植被和水体则有明显的冷岛效应;研究区热岛具有区域性集中与分散分布的特点,且以区域性热岛为中心向周边扩展;分析热岛强度剖面线发现,由于地形、植被覆盖度等因素影响,研究区热岛强度的南北差异较大,而东西差异较小;热岛分布与土地利用类型分布格局较为一致,但也有分布不一致性的区域,表现为城市热岛向非城市建设用地扩展。     

Evidence of urban-induced precipitation variability in arid climate regimes

The study employs a 108-year precipitation historical data record, global climate observing network observations and satellite data to identify possible anomalies in rainfall in and around two major arid urban areas, Phoenix, Arizona and Riyadh, Saudi Arabia. The analysis reveals that during the monsoon season, locations in northeastern suburbs and exurbs of the Phoenix metropolitan area have experienced statistically significant increases in mean precipitation of 12–14% from a pre-urban (1895–1949) to post-urban (1950–2003) period. Further analysis of satellite-based rainfall rates suggests the existence of the anomaly region (AR) over a 7-year period. The anomaly cannot simply be attributed to maximum topographic relief and is hypothesized to be related to urban-topographic interactions and possibly irrigation moisture. Temperature records suggest that Riyadh has experienced an adjustment in mean temperature in response to the growth of urban surfaces (e.g. the so-called urban heat island effect). While ground-based precipitation records also indicate an upward trend in mean and total precipitation in and around Riyadh in the last 10–15 years, it is difficult to attribute the increase to urbanization because other less urbanized stations in Saudi Arabia also show a similar increase. Recent satellite-based precipitation estimates indicate an AR 50–100 km north of Riyadh, but this study is not robust enough to conclusively link it to urbanization although certain climate-regime attributes suggests that it might be.     

城市热岛斑块遥感识别及空间扩张路径研究——以北京市为例

研究利用MODIS地表温度数据产品,引入概率阈值算法提升城市热岛斑块空间识别精度。在此基础上,构建城市热岛扩张指数将城市热岛斑块时空变化过程分解为飞地型、边缘型、填充型扩张模式和缩减型模式。基于土地利用变化过程,开展城市热岛斑块空间扩张模式的路径分析,准确识别城市热岛斑块空间扩张路径的来源和归趋。研究表明：2020年北京市夏季昼夜城市热岛斑块总面积分别为3932 km²和2 266 km²,占北京市总面积比例23.96%和13.81%。2005―2020年夏季昼夜城市热岛斑块面积比例分别增加43.40%和24.44%。增长型城市热岛斑块面积大于缩减型城市热岛斑块面积。边缘型扩张模式是增长型城市热岛斑块最主要的模式。耕地、城市建设用地、农村居民点是增长型城市热岛斑块主要的空间扩张路径。研究结果为揭示城市热环境形成过程和精细化管理提供理论依据和数据支撑。     

景洪市城市热岛效应对城市高温的影响及其防御对策

利用景洪市城郊长期对预测气象资源（１９６４￣１９９４）,分析了景洪城市热岛效应及其对城市高温的影响,并提出了防御对策。结果表明,进入８０年代以来,景洪市热岛效应日趋明显,且呈明显的季节性,即干季强于雨季,干季的夜间强于白天,雨季的白天强于夜间;热岛效应不仅增大了市区高温强度,同时增多了高温日数;减缓热岛效应的根本措施是大力发展绿化建设。     

Influence of urban expansion on the urban heat island effect in Shanghai

The urban heat island (UHI) effect resulting from rapid urbanization is attracting increasing attention among the global scientific community. This research analyzed the relationship between urban expansion and the UHI effect utilizing an integrated approach, including urban land interpretation and retrieving land surface temperature based on remote sensing, and spatial overlay analysis for revealing the relationship for different time periods between 1984 and 2014 in Shanghai, China. The results show that (1) the spatiotemporal changes in UHI are consistent with the expansion of urban land, and rapid urban expansion leads to an expansion of the UHI, in particular along roadways. (2) The mode of urban expansion is an important factor influencing the UHI effect. Urban sprawl (urban expansion in the edge-expansion way) is a form of typical expansion that leads to the rapid increase in the UHI. When the urban compactness ratio is less than 0.15, a compact design can effectively control the expansion rate of the UHI and mitigate its range of influence and intensity. However, when the urban compactness ratio is greater than 0.15, the urban design has a marked influence on the UHI ratio index: a more compact form produces a stronger UHI effect. So, finding an equilibrium between urban compactness ratio and urban expansion rate is good for effective urban management and planning.     

Developing open space networks in shrinking cities

Urban green spaces provide essential ecosystem services and improve resident quality of life, but open space networks are often fragmented by urban development, and it is difficult to reclaim natural lands after they have been built up. Shrinking cities (i.e., cities experiencing population decline) typically contain an abundance of vacant and abandoned residential buildings that are demolished for safety and maintenance reasons. The resulting empty lots can potentially be reclaimed as natural areas to defragment the green network and increase open space connectivity. To date however, planning efforts have largely ignored post-demolition land uses for these lots, allowing many to become empty wastelands. This research approaches this gap by presenting an alternative plan for residential demolition sites using landscape ecology principles and methods to incorporate them into the open space network. Using Buffalo, NY – a typical rustbelt shrinking city – as a case study, areas most at risk for experiencing demolitions are identified using a clustering technique, and each building within the cluster is assigned a likelihood it will be demolished using a logit model. Properties with the highest risk for demolition are then prioritized based on their ability to contribute to and connect the open space network using landscape connectivity metrics. Results indicate the approach can foster large increases in green network connectivity using small parcels (a 356% increase in total open space area was observed in this study after three years of purposeful selection), allowing cities to reclaim unused urban areas and defragment the open space network.     

城市热岛效应的影响机理及其作用规律——以上海市为例

以上海市为例,从土地利用规模和强度的变化、类型和布局的变化、利用方式的变化三个方面揭示其对热岛效应的影响机理;实证分析结果表明：（1）土地城市化是上海城市热岛强度的主要影响因素;就建成区扩张对热岛强度的具体影响而言,累积效应大于其增量效应;（2）工业化、房地产开发、人口增长对上海城市热岛强度均具有较大的影响;就经济发展和能源消耗对城市热岛强度的具体影响而言,密度效应通常大于其规模效应;就全社会房屋竣工面积、20 层以上高层建筑数量对热岛强度的影响而言,累积效应小于增量效应;就人口增长对城市热岛强度的具体影响而言,密度效应与规模效应大体相近;（3）土地利用和城市发展模式的差异导致了城市热岛效应的空间差异。     

城市土地利用/覆盖变化与热环境生态调控研究进展与展望

城市土地利用/覆盖变化(LUCC)与热环境生态调控是城市生态学和城市气候适应性关注的热点问题。在提出城市LUCC/空间结构与生态服务热调节功能连接的重要性的基础上,综述了城市土地利用变化、城市绿色基础设施在热岛减缓和气候适应性发挥的作用,评述了观测实验、定量遥感和过程模型方面以及热调控的进展情况。基于此认为,局地或区域尺度城市高精度结构组分高精度遥感探测方法、城市高精度下垫面多尺度(功能区/覆盖组分/构造或材质等)对局地气温和辐射能量平衡影响机理和定量贡献识别、城市生态系统热调节功能的城市地表结构组分调控阈值确定、以及区域或全球尺度城市土地利用/覆盖变化影响的生物地球物理机制定量化认知等,是未来重要的发展方向。     

The Slums of Aspen: Immigrants vs. the Environment in America's Eden. Lisa Sun-Hee Park and David Naguib Pellow

In the past decade, Beijing has experienced dramatic spatial restructuring. In this paper, we test whether the conventional monocentric model of urban spatial structure can explain recent developments in Beijing’s land market. Using official land transaction data from 2008 through 2012, we find that (1) for commercial, mixed-use, and residential land parcels, both land prices and development intensities do not decline with distance from the urban center; (2) for industrial land parcels, land prices increase with distance from the urban center. These insignificant and positive land-price gradients defy the predictions of the monocentric model; such results are explained by examining Beijing’s evolution from a monocentric to a polycentric spatial configuration, which has been driven by various urban planning efforts and institutional reforms. Our analysis of post-Olympic Beijing land market dynamics leads to a fresh understanding of the city’s emerging polycentric metropolitan structure.     

2003-2017年北京市地表热力景观时空分异特征及演变规律

利用2003-2017年MODIS地表温度数据,分别从数量、形状和结构角度揭示北京市不同季相和昼夜间地表热力景观时空分异特征,并进一步通过热力等级变化图谱及质心迁移轨迹揭示城市热力景观空间演变规律,探究热力景观等级转换生态过程。结论如下：① 城市地表热力景观季节和昼夜空间特征差异显著;② 中温区在城市热环境中占主导地位。白天中温区是最不稳定的热力景观等级;夜间次低温区和次高温区不稳定性增加;③ 地表热力景观等级变化以稳定型占主,反复变化型和前期变化型次之。地表热力景观等级通常呈现逐级递增或递减规律,山区呈现逐级降温趋势,北部城郊—山地交错地带表现出次低温和中温的反复转向,南部地区有一定的升温趋势;④ 2003-2017年高温区面积增大且质心向城市中心集中,低温区质心向城市外围扩散。生态涵养发展区对北京市地表热力景观质心迁移贡献率最高。热力景观时空分异特征及演变规律可为有效缓解城市热岛效应提供管理决策支持。     

Monitoring land changes in an urban area using satellite imagery,GIS and landscape metrics

Monitoring land changes is an important activity in landscape planning and resource management. In this study, we analyze urban land changes in Atlanta metropolitan area through the combined use of satellite imagery, geographic information systems (GIS), and landscape metrics. The study site is a fast-growing large metropolis in the United States, which contains a mosaic of complex landscape types. Our method consisted of two major components: remote sensing-based land classification and GIS-based land change analysis. Specifically, we adopted a stratified image classification strategy combined with a GIS-based spatial reclassification procedure to map land classes from Landsat Thematic Mapper (TM) scenes acquired in two different years. Then, we analyzed the spatial variation and expansion of urban land changes across the entire metropolitan area through post classification change detection and a variety of GIS-based operations. We further examined the size, pattern, and nature of land changes using landscape metrics to examine the size, pattern, and nature of land changes. This study has demonstrated the usefulness of integrating remote sensing with GIS and landscape metrics in land change analysis that allows the characterization of spatial patterns and helps reveal the underlying processes of urban land changes. Our results indicate a transition of urbanization patterns in the study site with a limited outward expansion despite the dominant suburbanization process.     

厦门市热岛强度与相关地表因素的空间关系研究

以厦门市为例,基于遥感影像与建筑普查数据,分析了各局部气候区中相关地表因素与热岛强度之间的空间响应规律,以及厦门市各局部气候区中热岛强度与相关地表因素的空间关系。结果表明:研究区热岛强度有显著的空间自相关性,高值区集中于东南部的建设用地及耕地和裸地,低值区聚集于湖泊、河流等水体、湿地以及北部、西北部的林地;普通回归模型不能有效解释空间中相关地表因素与热岛强度之间的关系;空间误差模型的拟合效果优于空间滞后模型,可以更准确分析地表因素与热岛强度之间的空间关系;各局部气候区中可以作为回归模型自变量的地表因素有所不同。作为回归模型的自变量时,植被指数、水体指数、天空视域因子与热岛强度呈负相关关系,建筑密度、不透水面比例与热岛强度呈正相关关系,而建筑体积密度、建筑平均高度、建筑高度差与热岛强度的相关性在各气候区中并不一致。根据研究结论建议保护"补偿区"、分隔"作用区",综合考虑规划实施策略的可行性,以有效缓解热岛效应。     

What controls the magnitude of the daytime heat sink in a desert city?

The aim of this study was to increase knowledge of the causes of cooling in desert cities. We used a time-series of Landsat images to characterize the changes in daytime land surface temperature during the period of rapid urbanization in Dubai. Changes in land cover and albedo were also quantified from Landsat data and the development of different land use types and variations in urban geometry were characterized. The results demonstrate that urban growth has promoted a heat sink and that all urban land use types contributed to this effect. Vegetation generated the largest cooling effect per unit surface area but impervious surfaces dominated the urban environment and are responsible for the majority of the heat sink created by the city. Changes in albedo were not causally related to the urban heat sink, however, variations in urban geometry, particularly the amount of shading cast by buildings, had some influence on the magnitude of cooling. This study provides evidence that the expansion of the heat sink during urbanization in a desert environment is influenced by the forms of land cover transition, the type of urban land use that is developed, the thermal properties of construction materials used and the geometry of the city environment that is constructed. Future research should concentrate upon understanding these mechanisms in order to plan future developments which maximize cooling and reduce the environmental impacts of desert cities.     

Policy-relevant indicators for mapping the vulnerability of urban populations to extreme heat events: A case study of Philadelphia

The recent global increase in extreme heat events linked to climate change is projected to continue. The additive effect of urban heat islands from impervious surfaces and urban heat emissions (e.g., from transportation and building cooling) exacerbates extreme heat events in urban areas, exposing dense populations to extreme heat with implications for human health. Ground- and satellite-based data on urban and suburban temperatures and vegetation over a historical period can help identify temporal and geospatial trends in heat exposure. A set of indicators has been developed to map the exposure, social sensitivity, and vulnerability of urban populations to heat wave health impacts. Guided by an Advisory Group of local planners in the pilot city of Philadelphia, localized trends of increasing urban extreme heat events using MODIS Land Surface Temperature (LST) data, confirmed with urban and non-urban temperature monitor data were identified. For the Philadelphia study area, the number of heat-event days in the urban setting has increased from approximately 4 days in 1980 to almost 12 days in 2013, while the non-urban setting has consistently experienced 5 days of heat events per year across the time period. Warmer micro-climates with limited vegetative cooling and elevated LSTs were also identified. The exposure indicator was combined with areas of high social sensitivity (e.g., low-income and elderly) to create a vulnerability indicator, showing significant overlap between highly exposed and highly sensitive populations. As a measure of the adaptive capacity of local governments to reduce the urban heat island, evidence of targeted vegetation increases or reduced localized temperatures linked to urban greening and cooling programs were sought, though none were of a scale to be identified by the 1 km satellite data utilized. The indicators have helped local decision makers to understand patterns of vulnerability, and may be used in the future to target adaptation actions and measure results (LST reduction or vegetation increase) from existing adaptation actions.     

Buying Development: Housing and Urban Growth in Guadalajara,Mexico

This study analyzes how Mexican federal housing policy affects the production of space and the housing landscape in Guadalajara, Mexico. Using a wide-ranging database of parcels developed in metropolitan Guadalajara, we map all housing developments from 1970 to 2000 and classify them into three categories that reflect different development processes. The greatly increased number of social-interest houses, and the large extension of land area developed since 1990 are explained by federal housing program reforms. Informal settlements remain a major path to home ownership, but the percentage of housing developments that are informal and the percentage of informally developed land have declined since the 1980s. We also discovered a trend of increasing land area devoted to low-density, élite enclaves, and analyzed marketing strategies and land use patterns that occurred in these newer developments. All of these outcomes reflect a neoliberal ideology that promotes consumption and the privatization of space, but largely excludes the urban poor. The result is higher rates of home ownership, but in an increasingly segregated and fragmented landscape poorly served by public infrastructure and lacking in amenities.