泰安市区不透水面覆盖度遥感估算研究

区域不透水面覆盖度是该区域城镇化程度、生态环境状况的重要指示因子。针对传统线性混合像元分解丰度图经常出现负值或者大于1的情况,采用完全约束最小二乘混合像元分解方法,利用泰安市市区Landsat8 OLI遥感影像提取了其不透水面分布状况,运用高分辨率遥感影像随机采样进行了精度检验,并对该区域不透水面空间特征进行了分析。结果表明:该文方法对泰安市市区不透水面分布提取的精度较高;植被、水体、高和低反照率不透水面4种光谱端元的线性组合,可以较好地模拟OLI影像的波谱特征;高、低反照率不透水面两种光谱端元可以很好地表达泰安市市区不透水面信息。     

Assessment with satellite data of the urban heat island effects in Asian mega cities

This study focuses on using remote sensing for comparative assessment of surface urban heat island (UHI) in 18 mega cities in both temperate and tropical climate regions. Least-clouded day- and night-scenes of TERRA/MODIS acquired between 2001 and 2003 were selected to generate land-surface temperature (LST) maps. Spatial patterns of UHIs for each city were examined over its diurnal cycle and seasonal variations. A Gaussian approximation was applied in order to quantify spatial extents and magnitude of individual UHIs for inter-city comparison. To reveal relationship of UHIs with surface properties, UHI patterns were analyzed in association with urban vegetation covers and surface energy fluxes derived from high-resolution Landsat ETM+ data. This study provides a generalized picture on the UHI phenomena in the Asian region and the findings can be used to guide further study integrating satellite high-resolution thermal data with land-surface modeling and meso-scale climatic modeling in order to understand impacts of urbanization on local climate in Asia.     

A New 3‐D Solar Radiation Model for 3‐D City Models

Estimates of solar radiation distribution in urban areas are often limited by the complexity of urban environments. These limitations arise from spatial structures such as buildings and trees that affect spatial and temporal distributions of solar fluxes over urban surfaces. The traditional solar radiation models implemented in GIS can address this problem only partially. They can be adequately used only for 2‐D surfaces such as terrain and rooftops. However, vertical surfaces, such as facades, require a 3‐D approach. This study presents a new 3‐D solar radiation model for urban areas represented by 3‐D city models. The v.sun module implemented in GRASS GIS is based on the existing solar radiation methodology used in the topographic r.sun model with a new capability to process 3‐D vector data representing complex urban environments. The calculation procedure is based on the combined vector‐voxel approach segmenting the 3‐D vector objects to smaller polygon elements according to a voxel data structure of the volume region. The shadowing effects of surrounding objects are considered using a unique shadowing algorithm. The proposed model has been applied to the sample urban area with results showing strong spatial and temporal variations of solar radiation flows over complex urban surfaces.     

Examining the impacts of urbanization on surface radiation using Landsat imagery

Metropolitan Beijing is facing many environmental problems such as haze and urban heat island due to the rapid urbanization. Surface shortwave, longwave, and net radiations are key components of the surface-atmosphere radiation budget. Since megacities are affected by the thermal radiation of complex landscape structures and atmospheric environments, quantitative and spatially explicit retrieval from remotely sensed data remains a challenge. We collected the surface radiation fluxes from seven fixed sites representing different land-use types to calibrate the local parameters for remotely sensed retrieval of net radiation. We proposed a remote sensing–based surface radiation retrieval method by embedding the underlying land covers and integrating the observational data. The improved method is feasible to accurately retrieve surface radiation and delineate spatial characteristics in metropolitan areas. The accuracy evaluation indicated that the difference between remotely sensed and in situ observed net radiation ranged within 0~± 40 W· m^?2. The root mean squared error of the estimated net surface radiation was 32.71 W· m^?2. The strongly spatial heterogeneity of surface radiation components in metropolitan Beijing was closely related to land-cover patterns from urban area to outskirts. We also found that the surface net radiation had a decreasing trend from 1984 to 2014, and the net radiation in the urban area was lower than that in the outskirts. According to the surface radiation budgets, urbanization resulted in the cooling effect in net radiation flux in the daytime, which was stemmed from low atmospheric transmittances from massive aerosol concentration and high surface albedo from light building materials.     

Spatial and Temporal Dynamics of Urban Heat Island and Their Relationship with Land Cover Changes in Urbanization Process: A Case Study in Suzhou, China

One of the significant environmental consequences of urbanization is the urban heat island (UHI). In this paper, Landsat TM images of 1986 and 2004 were utilized to study the spatial and temporal variations of heat island and their relationships with land cover changes in Suzhou, a Chinese city which experienced rapid urbanization in past decades. Land cover classifications were derived to quantify urban expansions and brightness temperatures were computed from the TM thermal data to express the urban thermal environment. The spatial distributions of surface temperature indicated that heat islands had been largely broadened and showed good agreements with urban expansion. Temperature statistics of main land cover types showed that built-up and bare land had higher surface temperatures than natural land covers, implying the warming effect caused by the urbanization with natural landscape being replaced by urban areas. In addition, the spatial detail distributions of surface temperature were compared with the distribution of land cover by means of GIS buffer analysis. Results show remarkable show good correspondence between heat island variations with urban area expansions.     

可持续城市化与国土空间优化

当前可持续国土空间发展面临重大挑战,面向生态文明和新型城镇化战略需求,探讨可持续城市化和国土空间优化的路径、方法和建模具有重要意义.可持续国土空间发展没有现成路径,探索国土空间优化的中国路径成为必然选择.城市及其周边是国土空间优化的关键地域,全球城市扩张研究表明,城市扩张具有路径依赖性、松散化和低密度化倾向,中国可持续...     

京津冀城市群1990—2015年城区时空扩展监测与分析

城区作为城镇化表征的重要指标,在城镇化时空扩展分析中有着重要的意义。然而,目前城区边界存在相关概念混杂导致对其认识缺乏统一、划定标准和数据来源缺乏一致性、遥感监测所用影像分辨率较低、以建设用地（不透水面）替代城区等问题。针对上述问题,参考住房和城乡建设部的建成区概念和城区地域分布范围,充分挖掘高分辨率遥感影像展现的城市景观和形态等空间可视化特征,从城市实际建设完成情况出发,本文提出了基于高分辨率影像和地理信息资料辅助的城区半自动化提取方法。获取了京津冀城市群153个县级以上城市的1990、2002、2015年的遥感影像、多元地理信息参考资料,开展了该区域的城区边界提取,并从时空扩展过程、城区空间形态及结构变化、城区扩展协调性、城区扩展占用土地类型4个方面对京津冀城市群1/4世纪的城镇化过程进行了统计分析。提出的技术方法和监测分析结果对于城镇化发展监测和城市规划实施评估具有重要的参考价值。     

地理模拟优化系统(GeoSOS)及其在地理国情分析中的应用

第一次全国地理国情普查工作已基本完成,需要对所获取的地理国情监测数据进行空间统计分析,以得到地理国情的时空分布模式、演变规律及发展趋势,形成地理国情信息和知识。地理国情监测生成的基础数据源,可用于土地资源集约利用、城乡及城市群协调发展、生态环境保护等问题的空间智能决策分析,但目前有效的模拟分析工具还比较缺乏。笔者提出的地理模拟优化系统(GeoSOS)理论框架,耦合了地理过程模拟预测和空间优化,为上述研究提供了有利的理论支持和实用工具。为进一步方便与GIS进行无缝的链接,本文提出了基于ArcGIS插件的GeoSOS以方便进行高效的地理模拟分析。并以快速城市化地区的城市扩张与生态保护研究为例,通过在地理国情信息分析中的应用,得到了一些重要的发现。模拟结果显示,按照现在的发展趋势,广东省优化开发区域在2020年其土地开发强度将超出规定的约束指标,并发现各区域均存在大量城乡建设用地占用生态保护压力等级高和较高地块的现象,而基于土地开发强度和生态保护双重约束的城镇化扩张能够在满足约束指标的同时获得更紧凑的景观格局。表明GeoSOS及其ArcGIS插件可以成为地理国情信息分析的有利工具,并给出了今后需解决的问题和发展方向。     

Urbanization effects on vegetation cover in major African cities during 2001-2017

Urbanization effects on vegetation cover (VC) have been analyzed in many regions. However, little attention has been paid to Africa, which has undergone rapid urbanization in recent decades. In this study, MODIS land cover and enhanced vegetation index (EVI) data were used to examine urbanization effects on VC in 59 large cities in Africa during 2001–2017. The ΔEVI (urban EVI minus rural EVI) was used to represent urbanization effects on VC. Major findings include: (1) for 59 cities averaged, annual ΔEVI averaged from 2015 to 2017 was -0.116. Negative annual ΔEVI (i.e. urban EVI lower than rural) were observed in 56 of 59 cities. (2) For 59 cities averaged, urban area increased 17.9% from 2001 (262.8 km²) to 2016 (309.8 km²). (3) Annual ΔEVI decreased significantly (p<0.05) in 44 of 59 cities for the period 2001–2017, and annual average area of urbanization effects on VC increased significantly in 40 of 59 cities. For 59 cities averaged, the percentage of urban area with significant decreasing trends of annual ΔEVI was 60.0%. Spatially, cities near the Gulf of Guinea showed more significant decreasing ΔEVI than cities in other regions. In addition, the trends and spatial distributions of urbanization effects on VC differed little by seasons. These results suggested that urbanization and its effects on VC in Africa should arouse more attentions.     

Area Delineation and Spatial-Temporal Dynamics of Urban Heat Island in Lanzhou City,China Using Remote Sensing Imagery

One of the key impacts of rapid urbanization on the environment is the effect of urban heat island (UHI). By using the Landsat TM/ETM+ thermal infrared remote sensing data of 1993, 2001 and 2011 to retrieve the land surface temperature (LST) of Lanzhou City, and by adopting object-oriented fractal net evolution approach (FNEA) to make image segmentation of the LST, the UHI elements were extracted. The G* index spatial aggregation analysis was made to calculate the urban heat island ratio index (URI), and the landscape metrics were used to quantify the changes of the spatial pattern of the UHI from the aspects of quantity, shape and structure. The impervious surface distribution and vegetation coverage were extracted by a constrained linear spectral mixture model to explore the relationships of the impervious surface distribution and vegetation coverage with the UHI. The information of urban built-up area was extracted by using UBI (NDBI-NDVI) index, and the effects of urban expansion on city thermal environment were quantitatively analyzed, with the URI and the LST grade maps built. In recent 20 years, the UHI effect in Lanzhou City was strengthened, with the URI increased by 1.4 times. The urban expansion had a spatiotemporal consistency with the UHI expansion. The patch number and density of the UHI landscape were increased, the patch shape and the whole landscape tended to be complex, the landscape became more fragmented, and the landscape connectivity was decreased. The heat island strength had a negative linear correlation with the urban vegetation coverage, and a positive logarithmic correlation with the urban impervious surface coverage.     

泉州市城市扩展的遥感监测及其城市化核分析

以泉州市为研究区,采用仿归一化植被指数(NDBI)和监督分类法对1989年和2000年的TM/ETM⁺图像进行城市空间信息提取,分析了城市空间扩展的趋势,探索出泉州市是以乡镇企业为城市化核来进行城市化过程的     

太原市“数字城管”数据库更新关键技术探讨

目前,“数字城管”数据库系统在全国主要城市中都有应用。随着城市化进程不断推进,城市建设日新月异,对系统中各类地理信息空间数据现势性提出较高要求,需结合城市建设不定期对数据库进行更新工作。本文结合太原市近年“数字城管”数据库更新工作,探讨了相关技术与方法,可对其他城市开展数据库更新工作提供借鉴作用。     

浙江城市群人口与用地规模的时空分异结构演变研究

结合夜间灯光与城市统计数据,应用城市位序-规模法则及人地异速生长模型,初步分析了浙江人口分布及人地关系,考虑到人口增长的特征,提出了加入滞后效应的修正模型,对浙江城市群长期的发展展开了动态研究.研究结果表明,浙江城市群结构体系较为成熟,但是随着经济发展,城市首位度逐步提高,人口逐渐呈现聚集状态;浙江城市群中的杭州、宁波...     

基于时间序列相似度的城市功能区识别研究

随着城市化的快速发展,城市空间结构愈发复杂,城市功能区的快速有效识别对资源的有效配置和城市规划具有重要意义.传统的功能区识别缺乏对居民这一城市空间活动主体的动态表征,而长时间序列的出租车数据能动态表征居民出行行为,进而反映城市空间结构.动态时间扭曲(DTW)距离比传统的欧氏距离更能有效挖掘高维数据,泛化后的LB_Keo...     

基于基础地理数据统计的长三角城市主城区空间格局扩展研究

在快速城镇化时期,城市主城区的空间格局变化最为显著,以其复杂性和扩展性为突出特征。研究其扩展变化对认识城镇化、优化城市空间结构等具有重要意义。本文在基础地理数据统计的基础上,对长三角城市主城区2002~2012年的空间扩展进行了分析,探索影响其演变的若干因素。     

城市不透水面覆盖度与地面温度遥感估算与分析

全球气候变暖和城市化的快速发展,导致了城市不透水面急剧增加和热岛效应日趋严重.本文综合利用多源遥感数据进行城市不透水面覆盖度(ISP)和地面温度(LST)的估算,实验结果较好地反映了城市ISP和LST的空间分布和变化状况;同时对二者之间的相关关系进行了简要分析,发现ISP与地面温度之间具有正相关关系,为通过绿化建设改善...     

Statistical analysis of surface urban heat island intensity variations: A case study of Babol city,Iran

The urban heat island is considered as one of the most important climate change phenomena in urban areas, which can result in remarkable negative effects on flora, concentration of pollutants, air quality, energy and water consumption, human health, ecological and economic impacts, and even on global warming. The variation analysis of the surface urban heat island intensity (SUHII) is important for understanding the effect of urbanization and urban planning. The objective of this study was to present a new strategy based on the Shannon’s entropy and Pearson chi-square statistic to investigate the spatial and temporal variations of the SUHII. In this study, Landsat TM, ETM+, OLI and TIRS images, MODIS products, meteorological data, topographic and population maps of the Babol city, Iran, from 1985 to 2017, and air temperature data recorded by ground recorder devices in 2017 were used. First, Single-Channel algorithm was used to estimate land surface temperature (LST), and the maximum likelihood classifier was employed to classify Landsat images. Then, based on LST maps, surface urban heat island ratio index was employed to calculate the SUHII. Further, several statistical methods, such as the degree-of-freedom, degree-of-sprawl and degree-of-goodness, were used to analyse the SUHII variation along different geographic directions and in various time periods. Finally, correlation between various parameters such as air temperature, SUHII, population variation and degree-of-goodness index values were investigated. The results indicated that the SUHII value increased by 24% in Babol over different time periods. The correlation coefficient yielded 0.82 between the values of the difference between the mean air temperature of the urban and suburbs and the SUHII values for the geographic directions. Furthermore, the correlation coefficient between the population variation and the degree-of-goodness index values reached 0.8. The results suggested that the SUHII variation of Babol city had a high degree-of-freedom, high degree-of-sprawl and negative degree-of-goodness.     

基于混合光谱分解的城市不透水面分布估算

城市化的一个重要表现就是不透水面分布比率的上升,城市内部不透水面分布是城市生态环境的一个重要指标。对于规模较大的大城市,采用高性价比的中等分辨率影像,获取不透水面的分布,是当前国际研究的一个热点。本研究利用Landsat 7的ETM 影像,在线性光谱分解的技术上,提取了上海市的不透水面分布并对其空间特征进行了分析。研究揭示,ETM 影像对于城市尺度的信息提取,其成本是较低的;对于城市地域来说,利用植被、高反照度、低反照度和裸露的土壤四种最终光谱端元的线性组合,可以较好地模拟ETM 波谱特征,而除了水面以外的高反照度、低反照度两种最终光谱端元,可以较好地表达城市不透水表面信息。结果显示,利用中等分辨率影像对上海中心城区不透水面分布提取的精度还是令人满意的,总体上,上海市不透水面分布比率较高,不透水面分布的空间差异进一步揭示了城市土地覆被空间结构以及城市空间扩展的差异性。     

Defining hydroclimatic regions using daily rainfall characteristics in the southern Appalachian Mountains

ABSTRACT

This paper addresses warm season hydroclimatic variability in the southern Appalachian region of the southeastern U.S., where precipitation can vary as much as 127?mm or more, with maximum seasonal totals exceeding 736?mm in extreme cases. Despite the occurrence of droughts, floods, and their socioecological impacts, hydroclimate variability is still poorly understood. This study characterizes the regional scale variations in the hydroclimate by examining the daily distribution of precipitation patterns in different topographic environments. Parameter-elevation relationships on independent slopes model (PRISM) gridded precipitation estimates are used to identify the location and frequency of different types of rainfall events. Several types of clustering algorithms are used as a regionalization approach to define areas where the precipitation regime exhibits similarities in its frequency of occurrence. The results are compared with internal validation statistics and a visualization is used to assess how well the resulting hydroclimatic regions align with different topographic environments. This study reveals the intricate spatial footprint of dry and wet regimes and demonstrates how clustering applications can be used with gridded climate data to determine where extremes are most likely to develop across mountain catchments.