《城市气象学》课件：05-3城市热岛-影响.ppt

1、Ch5 Urban Heat Islands（UHIs）三、三、UHIs 影响影响四、四、UHIs 减缓措施减缓措施五、五、UHI的文献评述的文献评述三、三、UHIs 影响影响城市中由于在天气条件适宜时，经常会出城市中由于在天气条件适宜时，经常会出现热岛效应，这就直接或间接地对当时当地现热岛效应，这就直接或间接地对当时当地有关气候要素，居民生活和城市经济产生多有关气候要素，居民生活和城市经济产生多种影响。有有利的一面，也有不利的一面。种影响。有有利的一面，也有不利的一面。1. 空调（取暖）度日数、积雪、霜冻空调（取暖）度日数、积雪、霜冻2. 健康影响健康影响3. 对能源消耗的影响对能源消耗的影

2、响4. 对风云雨的影响（以后介绍）对风云雨的影响（以后介绍）1、度度日日数数2、健康、健康l盛夏高温会降低工作效率。据统计如以气温盛夏高温会降低工作效率。据统计如以气温15时的工效为时的工效为100，则，则25时为时为92.5，35时为时为84.3。据武汉气象台统计当最高气温大于。据武汉气象台统计当最高气温大于37时，时，则中署病人急剧增多。则中署病人急剧增多。lWithin the United States alone, an average of 1,000 people die each year due to extreme heat.3、能源消耗、能源消耗lAnother cons

3、equence of urban heat islands is the increased energy required for air conditioning and refrigeration in cities that are in comparatively hot climates. The Heat Island Group estimates that the heat island effect costs Los Angeles about US$100 million per year in energy. Conversely, those that are in

4、 cold climates such as Moscow, Russia would have less demand for heating. However, through the implementation of heat island reduction strategies, significant annual net energy savings have been calculated for northern locations such as Chicago, Salt Lake City, and Toronto.四、四、UHIs 减缓措施减缓措施减缓热岛强度的主要

5、措施：减缓热岛强度的主要措施：l 屋顶、地面的材料和颜色屋顶、地面的材料和颜色l 绿化绿化10绿化降温效应11数值模式试验的几种情况数值模式试验的几种情况1214:00时温度差（反照率0.12-0.25) 14:0014:00时时10m10m高处水平面位温差分布（高处水平面位温差分布（）等值线数字建筑物反照率等值线数字建筑物反照率0.120.12时位温建筑物反照率时位温建筑物反照率0.250.25时位温时位温建筑物反照率建筑物反照率0.12 0.12 树木叶面指数树木叶面指数5.0 5.0 草地叶面指数草地叶面指数2.0 2.0 无屋顶绿化无屋顶绿化 14:00时温度差（屋顶绿化有-无） 14

6、:00 14:00时时10m10m高处水平面位温差分布（高处水平面位温差分布（）等值线数字屋顶绿化时位温屋顶无绿化时位温等值线数字屋顶绿化时位温屋顶无绿化时位温建筑物反照率建筑物反照率0.12 0.12 树木叶面指数树木叶面指数5.0 5.0 草地叶面指数草地叶面指数2.0 2.0 屋顶绿化叶面指数屋顶绿化叶面指数2.02.014:00时温度差（叶面指数10.0-5.0) 14:0014:00时时10m10m高处水平面位温差分布（高处水平面位温差分布（）等值线数字树木叶面指数为等值线数字树木叶面指数为10.010.0时位温树木叶面指数为时位温树木叶面指数为5.05.0时位温时位温建筑物反照率建

7、筑物反照率0.12 0.12 树木叶面指数树木叶面指数10.010.0 草地叶面指数草地叶面指数2.0 2.0 无屋顶绿化无屋顶绿化 五、关于五、关于UHI的文献评述的文献评述介绍一篇比较介绍一篇比较“另类另类”的文章的文章In the modern era of urban climatology, much emphasis has been placed on observing and documenting heat island magnitudes in cities around the world. Urban climate literature consequently

8、boasts a remarkable accumulation of observational heat island studies. Through time, however, methodologists have raised concerns about the authenticity of these studies, especially regarding the measurement, definition and reporting of heat island magnitudes.AbstractThis paper substantiates these c

9、oncerns through a systematic review and scientific critique of heat island literature from the period 19502007. The review uses nine criteria of experimental design and communication to critically assess methodological quality in a sample of 190 heat island studies. Results of this assessment are di

10、scouraging: the mean quality score of the sample is just 50 percent, and nearly half of all urban heat island magnitudes reported in the sample are judged to be scientifically indefensible. Two areas of universal weakness in the literature sample are controlled measurement and openness of method:one

11、-half of the sample studies fail to sufficiently control the confounding effects of weather, relief or time on reported urban heat island magnitudes, and three-quarters fail to communicate basic metadata regarding instrumentation and field site characteristics. A large proportion of observational he

12、at island literature is therefore compromised by poor scientific practice. This paper concludes with recommendations for improving method and communication in heat island studies through better scrutiny of findings and more rigorous reporting of primary research.The following scientific criteria wer

13、e developed for the purpose of assessing methodological quality in the heat island literature sample:Operational test and conceptual model are aligned;Operational definitions are explicitly stated;Instrument specifications are explicitly stated;Site metadata are appropriately detailed; Field sites a

14、re representative of the local-scale surroundings;Number of replicate observations is sufficiently large;Weather effects are passively controlled;Surface effects are passively controlled;Temperatures are measured synchronously.1. Operational test and conceptual model are alignedThe operational test

15、of the investigation is aligned with the conceptual model of a canopy-layer UHI. The test for this model invokes air temperature measurement below roof level in urban environments, and in the turbulent surface layer of rural environments.2. Operational definitions are explicitly statedOperational de

16、finitions of UHI magnitude or intensityare explicitly stated in the report, or made implicitthrough its discussion or presentation of data. Operational definitions reveal the measurement variables and field sites used to quantify UHI magnitude.3. Instrument specifications are explicitly statedInstru

17、ment specifications are explicitly stated in thereport, or made implicit through discussion or presentation of data. Instrument specifications include type, mounting and measurement4. Site metadata are appropriately detailedSite metadata are appropriately detailed in the report.Metadata include a lo

18、cal- or regional-scale map,sketch or photograph of the study area, and one ormore quantitative indicators of micro- or local-scalesurface exposure, roughness or cover at the field sitesused to quantify UHI magnitude.5. Field sites are representative of the local-scale surroundings; The micro-scale s

19、ettings of the field sites used toquantify UHI magnitude are approximately representative, in surface materials, geometry and human activity, of the local-scale surroundings.6. Number of replicate observations is sufficiently largeThe number of replicate heat island observations ina report is suffic

20、iently large to meet the stated aimsof the study and to yield representative and reliableestimates of UHI magnitude.7. Weather effects are passively controlled The extraneous effects of weather on UHI magnitudeare passively controlled. Computations of UHImagnitude use temperatures measured in relati

21、velysteady-state weather: no passing fronts, strong advection, or precipitation.8. Surface effects are passively controlledThe extraneous effects of surface relief, elevation andwater bodies on UHI magnitude are made sufficientlysmall through planned sampling design, or made sufficiently known throu

22、gh discussion and recognition of their influences on observed heat island magnitudes.9. Temperatures are measured synchronouslyTemperatures used to quantify UHI magnitude aremeasured synchronously. Inhomogeneities resultingfrom non-synchronous measurement are acknowledgedas such and adjusted to a co

23、mmon base time.Geographic distribution of heat island observations in the literature sample. The heat island observations reported in the literature sample are distributed across 11 continental realms and 221 cities and townsFrequency distribution of the heat island literature sample (N = 190) by sc

24、ientific criterion and aggregate pass/fail ratios.Discussion 1、The first area for generalisation is operationalisation of concepts. The literature is reasonably successful in this regard, as most studies demonstrate good conceptualunderstanding of the heat island effect and establish appropriate def

25、initions to test these concepts.2、The second area for generalisation is controlled measurement. The literature is generally poor in this regard. Approximately half of all heat island studies fail to sufficiently control their measurements for the confounding effects of weather, relief or time.3、The

26、third area for generalisation is openness of method. The literature is highly inadequate in this area, with three-quarters of the sample failing to communicate, in most basic terms, the precision of instruments used to measure UHI magnitude and the physical nature of the surfaces surrounding those i

27、nstruments at the time of measurement.Recommendations and closing remarks1、Reduce the spatial and temporal resolution of your data. For the purpose of quantifying UHI magnitude, fewer field sites in representative locations is preferable to more sites in unrepresentative locations. Likewise, a small

28、er dataset of controlled measurements is preferable to a larger dataset of uncontrolled measurements. A simple comparison of two representative sites will provide a reasonably good measure of UHI magnitude, provided that the measurements sufficiently regulate the effects of weather, relief, time and

29、 random variation.2、Follow standardised guidelines for site reporting.Guidelines in Aguilar et al. (2003) and Oke (2004)include descriptive templates for reporting the micro-, local- and meso-scale settings of temperature measurements in urban and rural environments. The information contained in the

30、se templates is essential to any heat island paper and to proper interpretation and comparison of its reported UHI magnitudes.3、Disclose the limits of your data. Observational data in environmental science are limited in their certainty and reliability. Like all climate observations, UHI measurement

31、s are limited by the complexities of the surfaceatmosphere system and by the technical capacity of our instruments to sample that system. Public statements claiming exact and absolute values of UHI magnitude are unjustified because the phenomenon being measured is inherently complex and difficult to

32、 access. Honest reporting of limitations and errors in observation is the best practice for sharing and advancing knowledge of UHIs. Public statements should instead claim reasonable estimates of UHI magnitude, and couch these estimates in round figures, within margins of instrumental error, and wit

33、h a tone of caution.4、Use terminology with discretion. The term “urbanheat island” is used irresponsibly in the literature todescribe all observed city-country temperature differences regardless of the causes behind those differences. If the temperature differences in a particularcity are caused pri

34、marily by weather or topographicinterferences, then the perceived heat island shouldnot be described as an urban-induced one.5、Never accept UHI magnitudes at face value. Behindevery reported estimate of UHI magnitude is an extenuatingset of circumstances. These circumstances are both experimental (e

35、.g. definition, instrumentation and measurement) and environmental (e.g. weather, climate and topography). No estimate of UHI magnitude is of any value to the public unless its extenuating circumstances are fully disclosed. Public comparisonof UHI magnitudes in the literature is risky because these

36、circumstances are often not reported or properly understood. Especially risky is the unqualified comparison of UHI magnitudes based on population or land use.These five recommendations call on the critical minds of research reviewers and heat island investigators to scrutinise the literature, weigh

37、its results and ultimately question its validity. Awareness, critique and revision of method are important stages in this process, as is demand for reduced but more responsible reporting of primary research. If climate modellers, weather forecasters, city planners, urban engineers and building architects are to be convinced of the serious environmental and social implications behind the UHI effect, heat island researchers must first produce results that can be trusted.The end of CH05 UHIs