The diurnal and seasonal characteristics of urban heat island variation in Beijing city and surrounding areas and impact factors based on remote sensing satellite data

Based on the land surface temperature (LST), the land cover classification map,vegetation coverage, and surface evapotranspiration derived from EOS-MODIS satellite data, and by the use of GIS spatial analytic technique and multivariate statistical analysis method, the urban heat island (UHI) spatial distribution of the diurnal and seasonal variabilities and its driving forces are studied in Beijing city and surrounding areas in 2001. The relationships among UHI distribution and landcover categories, topographic factor, vegetation greenness, and surface evapotranspiration are analyzed. The results indicate that: (i) The significant UHI occur in Beijing city areas in the four seasons due to high heat capacity and multi-reflection of compression building, as well as with special topographic features of its three sides surrounded by mountains,especially in the summer. The UHI spatial distribution is corresponding with the urban geometry structure profile. The LST difference is approximately 4-6℃ between Beijing city and suburb areas, comparatively is 8- 10℃ between Beijing city area and outer suburb area in northwestern regions. (ii) The UHI distribution and intensity in daytime are different from nighttime in Beijing city area, the nighttime UHI is obvious. However, in the daytime, the significant UHI mainly appears in the summer, the autumn takes second place, and the UHI in the winter and the spring seem not obvious. The surface evapotranspiration in suburb areas is larger than that in urban areas in the summer, and high latent heat exchange is evident, which leads to LST difference between city area and suburb area. (iii) The reflection of surface landcover categories is sensitive to the UHI, the correlation between vegetation greenness and UHI shows obviously negative.The scatterplot shows that there is the negative correlation between NDVI and LST (R2 = 0.6481).The results demonstrate that the vegetation greenness is an important factor for reducing the UHI,and large-scale construction of greenbelts can considerably reduce the UHI effect.     

夜间灯光遥感对城市发展类动能与相似性评估

评估城市发展水平与制定城市规划和城市发展政策息息相关.已有研究表明人口、国内生产总值(GDP)等统计数据和夜间灯光遥感数据能够用来衡量城市发展水平,但大多研究只关注城市发展总量,忽视了发展速度对城市发展的影响.因此,本文基于2012年—2019年Suomi NPP-VIIRS(Suomi National Polar-...     

标度律视角的城市效能测度及中国城市多维要素效能分析

"城市标度律"(urban scaling laws)揭示了城市系统中城市人口和城市要素间普遍存在的非线性规模缩放关系,但目前大多数城市评价忽视了这种关系,常使用人均指标比较不同规模的城市,这会导致评价结果偏差.为此,考虑城市人口和城市要素间的非线性规模缩放关系构建了要素效能指数,用以修正城市规模的影响,度量城市要素实...     

城市地质调查标准化建设系统

城市地质调查工作是优化城市空间结构、建设智慧城市、提高城市宜居水平的基础保障和重要支撑。笔者立足于新时期城市发展建设需求,建立了包括空间、资源、环境、灾害等方面的多要素城市地质调查系统;在全面借鉴国外发达城市有益经验的基础上,充分考虑国家政策导向,从工作内容、技术方法、成果应用3个维度分别提出了城市地质调查8个子系统的标准化建设方案;根据全球地学发展潮流和多学科交叉融合的时代特征,尝试提出了城市地质调查创新系统的未来建设,旨在探索城市地质调查的新途径、新思路和新方法。     

绵阳地区白垩系岩石风化过程的生态效应

论述了四川绵阳地区白垩系七曲寺组砂岩、泥岩风化过程的信息动态及其对森林植被的生态效应，为长江上游水土保持防护林提供开发信息。     

昆明城市气候水平空间分布特征

以昆明城市为研究对象，对城市西南-东北剖线的实测资料比较研究，从气温、水汽压、相对湿度、风速、风向等方面分析了昆明城市气候特征、变化规律及城市热岛效应。研究表明：在昆明存在热岛效应，以夜间最为明显，其最强度效应可达5.0℃，出现时刻（3时）与国内外多数研究结果（傍晚）有所不同；昆明城市昼间呈现明显的干岛效应。所得结论可为探讨昆明城市气候特片和形成机制，城市环境污染防治及建筑规划、设计等提供依据。     

城市生态安全水平的物元评判模型研究

作为人口高度集聚的人工生态系统,城市生态系统的安全性更加具有脆弱性。该文选取了若干公认的反映城市生态安全水平指标,建立了类型识别的物元评判模型。应用于我国十大城市,得出以下结论:处于"较安全"的城市有南京市、深圳市、大连市;处于"临界安全"的城市有上海市、广州市、南昌市、合肥市;处于"不安全"的城市有天津市、武汉市。评价结果基本与实地相符,说明建立的物元评判模型是可行的。     

黑麦草在净化富营养化水的人工湿地生态工程中的作用

在人工湿地生态工程中利用黑麦草(Lolium perenne L．)净化污水，得到了较好的效果。结果表明：利用黑麦草在冬春季节的生长，可使亚热带地区人工湿地常年运行，黑麦草在3—4月份对水体就有明显的净化作用。在春夏季节，特别在5月份黑麦草可以获得较高的生物量和N、P的积累量，因而净化贡献最大。从产草量方面考虑，延长黑麦草的生长期能获得较高的生物量；从植物体所含营养物质状况和饲用价值看，增加收割次数的黑麦草N、P含量高，饲用价值高；但从黑麦草对污水中N、P的吸收和积累量方面考虑，收割次数过高则不利于黑麦草对污水的净化及N、P的累积。从上述几方面综合考虑，在黑麦草整个生长期收割次数以2．3次为宜。     

From economic integration to socioeconomic inclusion: day labor worker centers as social intermediaries

Day labor worker centers have emerged as an important mode of regulatory action in the informal economy of major US cities. Research suggests that these organizations are beneficial in improving employment outcomes experienced by migrant workers engaged in this labor market sector. Yet, the extent to which these organizations impact the social integration of this working population remains relatively undeveloped in the literature. Using data from the National Day Labor Survey, we examine the impact of day labor worker centers on the level of social inclusion experienced by migrant day laborers. We find that worker centers have a modest, but statistically significant, impact on the levels of social integration experienced by this working population and that this varies from city to city. Ultimately we argue that the social intermediary role of these organizations may offer a type of counter mobilization necessary to promote the socioeconomic integration of this working population, but that issues of capacity remain.     

重庆城区浓雾的基本特征

统计分析沙坪坝1951～2002年间发生的浓雾事件，结合2001年12月重庆市雾的外场试验资料，探索重庆市主城区浓雾的基本特征。重庆主城区浓雾随年代演变有减缓趋势；主城区浓雾是自然雾与烟尘等的混合物，河谷及城市效应使雾更浓；城市中出现浓雾的大气边界层特征是在近地面层有逆温及增湿降温现象；高浓度气溶胶的净辐射效应阻碍白天混合层发展，使大气边界层趋于稳定，它是重庆连续几天有雾的原因之一；浓雾具有一定的湿沉降作用，能有限地清洁空气；有浓雾的天气条件下，建议降低污染物的排放总量，以避免严重大气污染事件发生。