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1.
以澳大利亚阿德莱德中心城区为研究区,基于高分辨率城市三维建筑物数据计算得到天空开阔度 (sky view factor,SVF) 与迎风面积指数 (frontal area index,FAI),并将其与晴好天气下四季的城市热岛强度进行相关性分析。结果表明:晴好天气下,阿德莱德城市热岛强度 (urban heat island intensity,UHII) 在2010—2011年四季均呈现出夜间强、白天弱的变化特征。SVF与UHII在夜间呈显著线性负相关,白天呈线性正相关;而FAI与UHII在四季的夜间和早晨时段呈对数关系,白天呈线性负相关。SVF和FAI对不同季节、不同时刻的城市热岛影响不同,在不同空间尺度下的适用性也存在差异,SVF在不同空间尺度下适用性更强。 相似文献
2.
Summary The sky view factor (SVF) is used in forest, road and urban climatology to characterise radiative properties. We now propose
a method suitable for forest canopies using the raster based and commercially available software IDRISI. It uses quadratic
pixels in rows and columns in a scanned equiangular fish-eye image. A threshold value is chosen to divide the image into sky
and non-sky areas. The resulting image is then multiplied with a sky view weight image, where the weights of the pixels depend
on the angular distance from zenith. The sum of pixel products gives the SVF. Quality analysis of the method is also performed.
The choice of threshold value gives some uncertainties due to leaves reflecting sunlight. This error will be reduced by observing
details (branches etc.) in the image and by choosing an overcast day for capturing the image. The precision range for SVF
calculations will be better than 0.1.
Received November 22, 1999 Revised July 17, 2000 相似文献
3.
《Atmospheric Science Letters》2001,2(1-4):155-165
It is now possible to generate large quantities of sky view factor (SVF) values due to advances in digital techniques for calculating SVF from hemispherical images. Coupling image acquisition with Global Positioning System (GPS) data now enables transects to be accurately placed, enabling site-specific SVF analysis in relation to street geometry. This paper examines SVF transects through four land cover classes. The findings indicate that although SVF averages are distinctly different in each of the land cover types, an average SVF value for a particular land use type is not a sufficient estimate at street resolution. 相似文献
4.
Poor daytime and night-time micrometeorological conditions are issues that influence the quality of environmental conditions and can undermine a comfortable human lifestyle. The sky view factor (SVF) is one of the essential physical parameters used to assess the micrometeorological conditions and thermal comfort levels within city streets. The position of the visible sky relative to the path of the sun, in the cardinal and ordinal directions, has not been widely discerned as a parameter that could have an impact on the micrometeorological conditions of urban streets. To investigate this parameter, different urban streets that have a similar SVF value but diverse positions of visible sky were proposed in different street directions intersecting with the path of the sun, namely N–S, NE–SW and NW–SE. The effects of daytime and night-time micrometeorological variables and human thermal comfort variables on the street were investigated by applying ENVI-met V3.1 Beta software. The results show that the position of the visible sky has a greater influence on the street’s meteorological and human thermal comfort conditions than the SVF value. It has the ability to maximise or minimise the mean radiation temperature (Tmrt, °C) and the physiological equivalent temperature (PET, °C) at street level. However, the visible sky positioned to the zenith in a NE–SW or N–S street direction and to the SW of a NW–SE street direction achieves the best daytime micrometeorological and thermal comfort conditions. Alternatively, the visible sky positioned to the NE for a NW–SE street direction, to the NW and the zenith for a NE–SW street direction and to the zenith for a N–S street direction reduces the night-time air temperature (Ta, °C). Therefore, SVF and the position of the visible sky relative to the sun’s trajectory, in the cardinal and ordinal directions, must be considered during urban street planning to better understand the resultant micrometeorological and human thermal comfort conditions. 相似文献
5.
The role of radiative-convective interaction in creating the microclimate of urban street canyons 总被引：2，自引：2，他引：2
Hanna Swaid 《Boundary-Layer Meteorology》1993,64(3):231-259
An approximate sky view factor (SVF) has been developed, which is capable of estimating the mean rate of net longwave radiant energy loss from urban street canyons. Reduced scale models of typical canyon geometries were used in outdoor tests to verify the predictions of radiant fluxes obtained using the proposed SVF. Air-surface temperature differences from the scale models are used together with hypothesized within-canyon airflow patterns to determine some quantitative characteristics of the wind field in canyons. Simple correlations are proposed for the relationship between mean in-canyon and pedestrian-level flow speeds on the one hand, and the ambient (above roof-level) wind speed on the other hand. As expected, the height/width ratio of a canyon controls the form and magnitude of the flow within. 相似文献
6.
Charalampopoulos Ioannis Tsiros Ioannis Chronopoulou-Sereli Aik. Matzarakis Andreas 《Theoretical and Applied Climatology》2017,128(3-4):811-820
The purpose of this paper is to present a simple methodology to improve the evaluation of the human-biometeorological benefits of open spaces. It is based on two groups of new indices using as basis the well-known PET index. This simple methodology along with the accompanying indices allows a qualitative and quantitative evaluation of the climatic behavior of the selected sites. The proposed methodology was applied in a human-biometeorology research in the city of Athens, Greece. The results of this study are in line with the results of other related studies indicating the considerable influence of the sky view factor (SVF), the existence of the vegetation and the building material on human-biometeorological conditions. The proposed methodology may provide new insights in the decision-making process related to urban open spaces’ best configuration.
相似文献7.
Summary A measurement programme was conducted in G?teborg Sweden, to examine the spatial variations of incoming longwave irradiance
on calm, cloudless nights. Both regional and local spatial variations were examined. Incoming longwave irradiance data was
obtained from mobile car transects, and at a fixed site on a building roof at the city centre. Ancillary data included sky
view factor at various transect locations, and balloon soundings of air temperature and humidity on one night.
Measurements revealed that on average, incoming longwave irradiance at the fixed urban site was 11 W m
−2 higher than at the rural station, with varying differences for intervening sites. Bulk apparent sky emissivity was higher
at the most rural station compared to the fixed urban site, by about 0.03 on average. Nighttime balloon measurements and a
sensitivity analysis with a radiative transfer model argue that the bulk apparent sky emissivity differences stem mainly from
the temperature structure of the lower boundary layer which changes markedly from rural to urban areas.
A good relationship was found between sky view factor and incoming longwave irradiance for a range of urban and park locations.
The relationship applies to both individual nights and average data. Using a simple obstruction model, canyon wall temperatures
are derived, and the relationship between sky view factor and wall temperature is examined.
Received December 23, 1999 Revised May 5, 2000 相似文献
8.
利用1990,1994,2000,2005,2011,2013年夏季北京地区Landsat卫星资料、2009年数字高程资料计算气象站周边景观指标参数,结果表明:土地利用类型、气象站周边景观指数、建筑物高度及天空可视因子等参数能对气象探测环境的结构配置信息以数字化方式呈现。此外,景观指标参数和气象要素相关分析表明:对气温变化影响较大的景观指标参数主要有城镇面积、水体面积、最大斑块指数、最大斑块占城镇面积比例、蔓延度指数、平均分维数和天空可视因子。对绝对湿度影响较大的景观指标参数为城镇面积、水体面积、最大斑块指数、最大斑块占城镇面积比例、蔓延度指数、聚集度指数和天空可视因子。对小风占比影响较大的景观指标参数仅为水体面积、最大斑块指数和最大斑块占城镇面积比例。基于以上统计结果,提出了一套对探测环境进行评估的方法——景观指标评估法。利用该方法对北京市15个国家级地面气象观测站进行评估,结果表明:周围环境对观测资料影响程度最小的站为怀柔站;环境影响最大的站为丰台站、朝阳站。 相似文献
9.
The Influence Of Urban Canopy Configuration On Urban Albedo 总被引：6，自引：0，他引：6
Akira Kondo Megumi Ueno Akikazu Kaga Katsuhito Yamaguchi 《Boundary-Layer Meteorology》2001,100(2):225-242
We propose a calculation method for shortwave radiation flux and longwave radiation flux within the urban canopy and investigate the influence of urban canopy configuration on net radiation flux. In the assumed urban configuration, buildings of equal size are arranged in a regular lattice within the urban canopy. The net shortwave radiation flux and longwave radiation flux within the urban canopy were calculated by the photon tracking method based on the Monte Carlo method. The albedo value obtained by this method shows close agreement with experimental data, and the average sky view factor shows almost perfect agreement with the theoretical value. Moreover, we calculated the urban albedo for the urban canopy configuration including roads and building height distribution.%Moreover, we calculated net radiation within the urban canopy in %consideration of roads and building height distribution.We found that the sky view factor of the ground surface is high when building coverage is low, building height is low, open space by roads exists, and building height is non-uniform. Moreover, we found that the albedo value is high when building height is small, open space by roads is wide, and building height is uniform. The albedo value was found to vary in a complicated manner with change in building coverage. 相似文献
10.
Summary The focus is the analysis of urban Digital Elevation Models (DEMs) with image processing techniques. A brief review of existing
methods to derive sky view factors, building energy consumption and space syntax shows how well established parameters that
relate to airflow and dispersion (such as the height-to-width of urban canyons and the aerodynamic roughness length) can be
calculated. Other measures of urban directionality and periodicity, inspired by traditional image processing, are also introduced,
such as the Radon, Hough and Fourier transforms and the variance plot. Analyses of three case study sites in London, Toulouse
and Berlin are compared, showing considerable variation in the chosen parameters. Results suggest that the DEM format is an
extremely versatile tool to investigate the urban intermediate scale, allowing analyses that would be very difficult or impossible
to carry out using traditional vectorial models. 相似文献
11.
Numerical Modelling of Urban Heat-Island Intensity 总被引：1，自引：0，他引：1
B. W. Atkinson 《Boundary-Layer Meteorology》2003,109(3):285-310
A three-dimensional, non-hydrostatic, high-resolution numerical model was used toanalyse urban heat-island (UHI) intensity in an idealised but realistic configuration.The urban area was 20 km square and lay on flat land at about latitude 50° Nin a maritime climate. In the model the urban area was represented by anomalies ofalbedo, anthropogenic heat flux, emissivity, roughness length, sky-view factor (SVF),surface resistance to evaporation (SRE) and thermal inertia. A control simulationincluded all these factors and the resultant UHI structure, energetics and intensitywere validated against observations. The results also compared favourably withearlier simulations.A series of experiments was conducted in which successively one of the anomaliesthat represented the urban area was omitted from the control simulation so as toprovide the basis for an assessment of its effect. In daytime the individual effectsdue to albedo, anthropogenic heat, emissivity, SVF and thermal inertia ranged from0.2 to 0.8 °C. In common with albedo, anthropogenic heat, emissivity andSVF, the SRE aided the formation of a UHI; it was also the most important factorin increasing its intensity. The roughness length had the opposite effect. At nightemissivity, roughness length, SVF and SRE had effects ranging from 0.3 to0.75 °C, but the largest effect (2 °C) was due to the anthropogenicheat. These results showed a difference in the causes of daytime and nighttime UHIs.In daytime the roughness length and SRE were the most important factors affectingUHI intensity; at night the anthropogenic heat was the most important. The simulationssuggested that the size of the urban area had a minimal effect on UHI intensity. 相似文献
12.
Andreas Matzarakis Manuela De Rocco Georges Najjar 《Theoretical and Applied Climatology》2009,98(3-4):209-220
This case study highlights the implications of the 2003 heat wave for the city of Strasbourg, France. The urban centers of France and other European countries were particularly affected by the heat wave. In some urban areas, the mortality rate was 60% above the expected value (Institute de Veille Sanitaire, 2003). The 2003 heat wave demonstrated once again that populations in urban centers are much more affected by extreme meteorological events than people living in rural areas. The aim of this analysis is to explore differences in thermal comfort conditions of (a) the city center of Strasbourg, and (b) its hinterland. The differences in thermal conditions existing between rural and urban areas are quantified by using a bio-climatological index termed physiologically equivalent temperature (PET). This index is based on the human energy balance and builds a relevant index for the quantification of the thermal environment of humans. We calculate the PET for the years 2003 and 2004 to highlight the temporal changes in the severity of climate extremes. The spatial scope of this study is improved compared to previous works in the field through the inclusion of PET calculations for five different sites on a central place in Strasbourg (Place Kléber). The calculations are characterized by different sky view factors and are compared to the reference site, which is located in a rural area. In the rural hinterland (Entzheim), the analysis of PET indicates a strong cold thermal stress during the winter months but no significant stress in summer. In 2003, summer temperatures were sensed as warmer compared to other years, but did not reach the extreme temperatures that may cause severe heat stress. For both the rural and the urban study sites PET was higher in the summer of 2003 than in 2004, which reflects the inferior thermal conditions in the urban area during the heat wave in 2003. For the entire study period, urban and rural day-time PET reached similar maximal values. Strong differences in PET, however, were observed between the rural and urban areas at night-time. The study of PET for several study sites on a central place in the city (Place Kléber) of Strasbourg for the years 2003 and 2004 showed that the sites with a higher sky view factor present higher values than sites with a lower sky view factor. The comparison of these PET values (Place Kléber) to the results for the rural area showed that during the day and the night the rural city of Entzheim has the lowest PET. During the day, the site at Place Kléber, which is located under a tree, has the lowest PET. The comparison of PET for the years 2003 and 2004 shows that PET in 2003 was about 5 to 7 K higher. 相似文献
13.
Abel Antônio Silva Mariza Pereira de Souza Echer 《Meteorology and Atmospheric Physics》2013,120(3-4):201-212
Clouds are believed to reflect temporal climate changes through variations in their amounts, characteristics, and occurrence. In addition, they reflect both weather and climate in a region. In this work, a methodology to determine the local cloud cover (LCC) is proposed using sky images obtained from a ground-based instrument. Three years of sky images from an urban, tropical site were obtained and analyzed through that methodology. Monthly average LCC varied from 3 to 96 %, while seasonal average values were 68 % for summer, 54 % for spring, 46 % for fall, and 23 % for winter. LCC results show a clear seasonal dependence and a fair agreement (r 2 = 0.72) with satellite data, which typically underestimate the cloud cover in relation to LCC. Our analysis also suggests the possibility of a measurable link between LCC and natural events like the El Niño Southern Oscillation. 相似文献
14.
Summary. Building walls form an important component of the total surface area in cities, but are not generally considered in most
attempts to measure urban surface temperatures. A procedure which allows sampling of the spatial and temporal variation of
wall surface temperatures in urban areas is presented. Radiometric surface temperatures are monitored using an array of infrared
thermometers mounted on a moving vehicle. It is necessary to remove observations which view sky, or mixed sky and building
scenes. Distribution truncation and distribution modelling are investigated as methods to remove the unwanted observations.
Use of the traverse method in several urban areas reveals strong temporal variations in wall temperatures due to solar loading.
Significant spatial variations in temperatures suggest caution be used in the extrapolation of data from single canyon studies
to larger scales. Times of strong surface temperature contrast between different walls are linked to canyon and solar geometry.
In the light industrial and residential observation areas, north-south streets show mid-morning and late afternoon peaks of
approximately equal magnitude in the difference between wall surface temperatures. East-west streets show a single peak in
the hour following solar noon. The downtown study area, with streets oriented northeast-southwest and northwest-southeast,
shows a double wave pattern with one peak dominant. These patterns are of interest because they can lead to large biases in
remotely-observed surface temperature with view direction.
Received May 30, 1997 Revised July 20, 1997 相似文献
15.
The solar and longwave environmental irradiance geometry (SOLWEIG) model simulates spatial variations of 3-D radiation fluxes and mean radiant temperature (T mrt) as well as shadow patterns in complex urban settings. In this paper, a new vegetation scheme is included in SOLWEIG and evaluated. The new shadow casting algorithm for complex vegetation structures makes it possible to obtain continuous images of shadow patterns and sky view factors taking both buildings and vegetation into account. For the calculation of 3-D radiation fluxes and T mrt, SOLWEIG only requires a limited number of inputs, such as global shortwave radiation, air temperature, relative humidity, geographical information (latitude, longitude and elevation) and urban geometry represented by high-resolution ground and building digital elevation models (DEM). Trees and bushes are represented by separate DEMs. The model is evaluated using 5?days of integral radiation measurements at two sites within a square surrounded by low-rise buildings and vegetation in G?teborg, Sweden (57°N). There is good agreement between modelled and observed values of T mrt, with an overall correspondence of R 2?=?0.91 (p?<?0.01, RMSE?=?3.1?K). A small overestimation of T mrt is found at locations shadowed by vegetation. Given this good performance a number of suggestions for future development are identified for applications which include for human comfort, building design, planning and evaluation of instrument exposure. 相似文献
16.
Sebastian Schubert Susanne Grossman-Clarke Alberto Martilli 《Boundary-Layer Meteorology》2012,145(3):439-468
We develop a double-canyon radiation scheme (DCEP) for urban canopy models embedded in mesoscale numerical models based on the Building Effect Parametrization (BEP). The new scheme calculates the incoming and outgoing longwave and shortwave radiation for roof, wall and ground surfaces for an urban street canyon characterized by its street and building width, canyon length, and the building height distribution. The scheme introduces the radiative interaction of two neighbouring urban canyons allowing the full inclusion of roofs into the radiation exchange both inside the canyon and with the sky. In contrast to BEP, we also treat direct and diffuse shortwave radiation from the sky independently, thus allowing calculation of the effective parameters representing the urban diffuse and direct shortwave radiation budget inside the mesoscale model. Furthermore, we close the energy balance of incoming longwave and diffuse shortwave radiation from the sky, so that the new scheme is physically more consistent than the BEP scheme. Sensitivity tests show that these modifications are important for urban regions with a large variety of building heights. The evaluation against data from the Basel Urban Boundary Layer Experiment indicates a good performance of the DCEP when coupled with the regional weather and climate model COSMO-CLM. 相似文献
17.
Scale modelling is used to determine the relative contribution of heat transfer processes to the nocturnal cooling of urban parks and the characteristic temporal and spatial variation of surface temperature. Validation is achieved using a hardware model-to-numerical model-to-field observation chain of comparisons. For the calm case, modelling shows that urban-park differences of sky view factor (s) and thermal admittance () are the relevant properties governing the park cool island (PCI) effect. Reduction in sky view factor by buildings and trees decreases the drain of longwave radiation from the surface to the sky. Thus park areas near the perimeter where there may be a line of buildings or trees, or even sites within a park containing tree clumps or individual trees, generally cool less than open areas. The edge effect applies within distances of about 2.2 to 3.5 times the height of the border obstruction, i.e., to have any part of the park cooling at the maximum rate a square park must be at least twice these dimensions in width. Although the central areas of parks larger than this will experience greater cooling they will accumulate a larger volume of cold air that may make it possible for them to initiate a thermal circulation and extend the influence of the park into the surrounding city. Given real world values of s and it seems likely that radiation and conduction play almost equal roles in nocturnal PCI development. Evaporation is not a significant cooling mechanism in the nocturnal calm case but by day it is probably critical in establishing a PCI by sunset. It is likely that conditions that favour PCI by day (tree shade, soil wetness) retard PCI growth at night. The present work, which only deals with PCI growth, cannot predict which type of park will be coolest at night. Complete specification of nocturnal PCI magnitude requires knowledge of the PCI at sunset, and this depends on daytime energetics. 相似文献
18.
Abstract Radiance criteria for distinguishing low, middle, and high clouds in the 9.5–11.5 μm band of the infrared are developed and used to produce local cloud maps. The performance of this radiance contrast method for mapping clouds from the earth's surface is evaluated with a view to using the technique for objective observation of cloud amount and distribution in the sky hemisphere. Discrimination radiance formulas are developed using a multilayer, wavenumber‐specific infrared radiative transfer model including cloud parameters measured by other workers and atmospheric conditions measured by radiosonde. The clear sky radiance (N0) is the dominant independent variable in the discrimination formulas. The variation of N0 with time (primarily due to changes in atmospheric water vapour content) and zenith angle are found to be important in distinguishing cirriform clouds from clear sky and other clouds. The local cloud maps are produced by applying the discrimination radiances (in voltage form) to the output from a narrow‐view infrared radiometer pointed at a sky‐scanning mirror. It is necessary to assume that the radiance from a cloud observed at the surface decreases unambiguously with an increase in cloud base height. Cloud maps for five days in July 1978 indicate the mapping technique shows promise under a wide range of sky conditions. Cloud motions rapidly degrade the maps’ quality over time‐scales that are much less than the current manual cloud sampling period of 1 h. 相似文献
19.
Sigmund Fritz 《Meteorology and Atmospheric Physics》1962,13(2):186-198
Summary From April 2 to 7, 1960, the meteorological satellite Tiros I televised the Alps and the surrounding area. The Alpine mountains were snow covered but the river valleys and lakes were readily discernible in the pictures under clear sky conditions. The pictures show marked differences when the area was overcast as compared to times when the area was clear or partly cloudy. These differences are discussed with the aid of satellite pictures and surface cloud cover maps.
With 6 Figures
Dedicated toDr. W. Mörikofer on the occasion of his 70th birthday. 相似文献
Zusammenfassung Vom 2. bis 7. April 1960 hat der meteorologische Satellit Tiros I Fernsehaufnahmen der Alpen und der umliegenden Gebiete gemacht. Die Alpenberge waren damals schneebedeckt, dagegen waren die Flußtäler und Seen bei Schönwetter in den Bildern deutlich zu erkennen. Die Bilder zeigen markante Unterschiede, wenn das Gebiet von Wolken bedeckt war, im Vergleich zu den Bildern bei wolkenlosem oder nur teilweise wolkigem Wetter. Diese Unterschiede werden an Hand von Satellitenaufnahmen und von nach Bodenbeobachtungen entworfenen Bewölkungskarten diskutiert.
Résumé Le satellite météorologique Tiros I a effectué du 2 au 7 avril 1960 des prises de vue télévisées des Alpes et des régions avoisinantes. Les montagnes étaient alors recouvertes de neige, mais les vallées et les lacs sont, par ciel serein, nettement visibles sur les images. Ces images montrent des différences sensibles si les diverses régions ont un ciel couvert ou, au contraire, serein ou peu nuageux. On discute alors ces différences tant au moyen des images produites par le satellite que par des cartes de la nébulosité basées sur des observations au sol.
With 6 Figures
Dedicated toDr. W. Mörikofer on the occasion of his 70th birthday. 相似文献
20.
安徽省农业干旱综合监测技术及其业务试用 总被引：2，自引：1，他引：1
针对安徽省农业干旱业务服务需求,利用已业务应用的农业干旱指标:土壤墒情、累积湿润指数、植被供水指数,配合阶段降水量和降水日数,进行农业干旱综合监测指标和方法研究.综合指标中各因子权重的确定采用层次分析法.根据安徽省气候过渡区下垫面地表特征差异和云天状况,分别确定了湿润区、半湿润区的晴空和云覆盖4种状态下的各因子权重序列,均通过了一致性检验;建立了相应的农业干旱综合监测模型;确定了4要素和5要素农业干旱监测等级标准.综合模型概括了各单指标主体监测结果,有利于对农业旱情的综合判断,监测模型检验效果良好,可业务应用. 相似文献