Statistical and dynamical characteristics of the urban heat island intensity in Seoul

The statistical and dynamical characteristics of the urban heat island (UHI) intensity in Seoul are investigated for non-precipitation days and precipitation days using 4-year surface meteorological data with 1-h time intervals. Furthermore, the quantitative influence of synoptic pressure pattern on the UHI intensity is examined using a synoptic condition clustering method. The statistical analysis shows that the daily maximum UHI intensity in Seoul for non-precipitation days is strongest in autumn (4.8°C) and weakest in summer (3.5°C). The daily maximum UHI intensity is observed around midnight in all seasons except in winter when the maximum occurrence frequency is found around 08 LST. This implies that anthropogenic heating contributes to the UHI in the cold season. The occurrence frequency of the UHI intensity has a negatively skewed distribution for non-precipitation days but a positively skewed distribution for precipitation days. The amplitude of the heating/cooling rate and the difference in the heating/cooling rate between the urban and rural areas are smaller in all seasons for precipitation days than for non-precipitation days, resulting in weaker UHI intensities for precipitation days. The urban cool island occurs very often in the daytime, with an occurrence frequency being 77% of the total non-precipitation days in spring. The analysis of the impact of large-scale dynamical forcing shows that the daily maximum UHI intensity varies with synoptic pressure pattern, ranging from ?22% in spring to 28% in summer relative to the seasonal mean daily maximum UHI intensity. Comparison of the UHI intensity calculated using station-averaged temperatures to that based on the conventional two-station approach indicates that local effects on the UHI intensity are minimized by using multiple-station data. Accordingly, an estimation of the UHI intensity using station-averaged temperatures for both urban and rural areas is suggested.     

The impact of heat waves on surface urban heat island and local economy in Cluj-Napoca city,Romania

The association between heat waves and the urban heat island effect can increase the impact on environment and society inducing biophysical hazards. Heat stress and their associated public health problems are among the most frequent. This paper explores the heat waves impact on surface urban heat island and on the local economy loss during three heat periods in Cluj-Napoca city in the summer of 2015. The heat wave events were identified based on daily maximum temperature, and they were divided into three classes considering the intensity threshold: moderate heat waves (daily maximum temperature exceeding the 90th percentile), severe heat waves (daily maximum temperature over the 95th percentile), and extremely severe heat waves (daily maximum temperature exceeding the 98th percentile). The minimum length of an event was of minimum three consecutive days. The surface urban heat island was detected based on land surface temperature derived from Landsat 8 thermal infrared data, while the economic impact was estimated based on data on work force structure and work productivity in Cluj-Napoca derived from the data released by Eurostat, National Bank of Romania, and National Institute of Statistics. The results indicate that the intensity and spatial extension of surface urban heat island could be governed by the magnitude of the heat wave event, but due to the low number of satellite images available, we should consider this information only as preliminary results. Thermal infrared remote sensing has proven to be a very efficient method to study surface urban heat island, due to the fact that the synoptic conditions associated with heat wave events usually favor cloud free image. The resolution of the OLI_TIRS sensor provided good results for a mid-extension city, but the low revisiting time is still a drawback. The potential economic loss was calculated for the working days during heat waves and the estimated loss reached more than 2.5 mil. EUR for each heat wave day at city scale, cumulating more than 38 mil. EUR for the three cases considered.     

热浪对人体健康的影响及其研究方法

由于全球气候变化和城市热岛效应,热浪成为世界范围内频繁发生的极端天气事件,这使得热浪对人体健康的影响问题成为许多国际机构,如世界气象组织(WMO)、世界卫生组织(WHO)、联合国环境规划署(UNEP)和各国气象、环境和流行病等方面科学家关注的焦点.作者介绍近年来世界各地频繁发生的热浪及其原因、热浪对人体健康的影响、热浪研究的指标法、多元回归分析和天气气候分型等多种方法,同时也提出防御热浪的一些措施.     

基于均值—标准差改进的滨州市多时相热岛强度变化分析

为探究山东省滨州市热岛强度的时空分布及其变化特征,通过2001、2009和2018年夏季的3期Landsat数据实现地表温度反演,并基于热岛强度定义对传统的均值—标准差分级法进行改进,能够较好地消除因背景数据不一致而导致不同时期热岛强度数据难于对比的问题.在此基础之上,分析热岛效应及其变化的时空分布特征,并结合土地利用...     

A numerical study of atmospheric pollution over complex terrain in Switzerland

A pollution-related study has been carried out for the Swiss city of Bienne that is located in complex terrain at the foot of the Jura mountains. The study consists of an analysis of pollutant transport and dispersion from various emittors located in the city, using a coupled system of mesoscale and micro-scale atmospheric numerical models. Simulations of atmospheric flow with the mesoscale model over a 20 × 20 km domain (horizontal resolution: 500 m; vertical resolution: 250 m) are used to initialize a microscale model centered over the city. The domain of this latter model is 4 × 4 km (horizontal resolution: 100 m; vertical resolution: 10 m). Plume trajectories are computed in the micro-scale model, and are a function of the regional-scale flow field previously calculated by the mesoscale model. Results show that the flow — and hence the plume trajectories embedded within this motion field — an sensitive not only to channeling effects by the local valley systems, but also to local or regional meteorological effects resulting from cloud activity, urban heat island, and the direction of the synoptic scale flow with respect to the orientation of the Jura mointains.     

敦煌地区荒漠戈壁地表热量和辐射平衡特征的研究

利用2000年5月25日～6月17日"敦煌试验"在戈壁的微气象观测资料,分析了极端干旱地区晴天、阴天和降水等天气条件下的地表辐射平衡、热量平衡和土壤温度等微气象特征的日变化规律.发现在不同天气条件微气象特征有很大变化.但观测期间的平均微气象特征与晴天比较接近,天气过程的影响不是很大,平均的总辐射、净辐射和感热通量与晴天的比值在白天基本大于0.8.观测期间的平均Bowen比全天大于1,在白天都在10以上,最大超过100.     

Numerical study of the nocturnal urban boundary layer

A two-dimensional time-dependent Earth-atmosphere model is developed which can be applied to the study of a class of atmospheric boundary-layer flows which owe their origin to horizontal inhomogeneities with respect to surface roughness and temperature. Our main application of the model is to explore the governing physical mechanisms of nocturnal urban atmospheric boundarylayer flow.A case study is presented in which a stable temperature stratification is assumed to exist in the rural upwind area. It is shown through integration of the numerical model that as this air passes over a city, the heat is redistributed due to increased surface friction (and hence increased turbulent mixing). This redistribution of heat results in the formation of an urban heat island.Additional numerical integrations of the model are conducted to examine the dependence of induced perturbations on: (1) the upwind temperature inversion; (2) the geostrophic wind speed; and (3) urbanization. The results show a linear relationship between heat-island intensity and the rural temperature inversion with the heat island increasing in intensity as the upwind inversion becomes stronger; that the heat-island intensity close to the surface is inversely proportional to the geostrophic wind; and that the effects of anthropogenic heat cause an increase in the perturbation temperature with the perturbation extending to higher altitudes. From this study, we conclude that with an upwind temperature inversion, a city of any size should generate a heat island as a result of increased surface roughness. The heat-island intensity should increase with city size because of two factors: larger cities are usually aerodynamically rougher; and larger cities have a larger anthropogenic heat output.Research supported in part by NSF Grant GA-16822.     

Objective method for classifying air masses: an application to the analysis of Buenos Aires’ (Argentina) urban heat island intensity

Summary ?During recent years, numerous studies have examined the Buenos Aires urban climate, but the relationship between large-scale weather conditions and the Buenos Aires urban heat island (UHI) intensity has not been studied. The goal of this paper is to apply an objective synoptic climatological method to identify homogeneous air masses or weather types affecting Buenos Aires during winter, and to relate the results to the UHI intensity. A K-means clustering method was used to define six different air masses considering the 03:00, 09:00, 15:00 and 21:00 LT surface observations of dry bulb temperature, dew point, cloud cover, atmospheric pressure and wind direction and velocity at Ezeiza, the most rural meteorological station of the Buenos Aires metropolitan area (Fig. 1). Results show that the mean UHI intensity is at its maximum (2.8 °C) a few hours before sunrise when conditions are dominated by cold air masses associated with cold-core anticyclones, weak winds and low cloud cover. Inverse heat islands are found during the afternoon for all air masses indicating that surface processes are not dominant at that time. The relatively infrequent and warmest air mass is the only one that presents a mean negative urban-rural temperature difference (−0.1 °C) during the afternoon with the smallest diurnal cycle of the UHI intensity probably due to the prevailing high humidity and cloudy sky conditions. The paper provides an insight into the Buenos Aires urban–rural temperature difference under a variety of winter weather types and results could be useful to improve local daily temperature forecasts for the metropolitan area of Buenos Aires on the basis of the routine forecasts of weather types. Received October 24, 2001; revised June 12, 2002; accepted October 10, 2002     

A climatological analysis of four-day back trajectories from aliartos,Greece

Summary This study presents a flow climatology for Greece based on a survey of climate and synoptic weather types, and a five-year trajectory climatology. Isobaric back trajectories at the 850 and 700 hPa levels were calculated daily at 0 and 12 Z for the years 1983–1987 for the Aliartos, Greece EMEP station, using the Air Resources Laboratory (ARL) trajectory model. Trajectories were classified by direction and speed to examine monthly, seasonal and annual variability in flow characteristics. The main features of the flow are similar from year to year. Dominant transport sectors are NW and W, followed by N, SW and NE. Four-day back trajectories from NW and W usually originate from beyond 2,400 km, while those from other directions tend to originate closer to Greece. Cases of most rapid transport occur in January and December. Potential pollutant source regions are identified corresponding to preferred trajectory directions and distance ranges.With 6 Figures     

云南高原城市楚雄和大理热岛效应变化特征

利用1971-2000年楚雄市和大理市的气温、降水、相对湿度、平均风速等气候资料,分析了楚雄市和大理市两城市热岛效应变化特征,应用灰色关联度方法分析热岛强度发生变化的原因.结果发现:30年来楚雄市的热岛强度年变化在不断增强,而大理市热岛强度增加不如楚雄市明显,热岛强度月变化两城市基本一致,干季强,雨季弱;热岛强度日变化...     

基于Landsat卫星数据的山东临沂市热岛效应研究

利用Landsat卫星数据分别反演了2005年和2014年临沂市的地表温度和不透水层指数，分析了城市化进程对临沂市热岛效应的影响。结果表明，2005年临沂市表现为中等强度的热岛效应，2014年表现为强热岛效应。利用地面站点资料统计分析来看，2005～2014年，临沂市热岛强度总体呈波动增加的趋势,冬季最强，春秋季次之，夏季较弱。分析城市化因子发现，城市经济、人口、用电消耗、城市房屋面积增量等多个因素对城市热岛强度变化的影响，其相关系数分别为0.86、0.82、0.67、0.81，其中房屋面积增量与热岛强度增强密切相关。从不透水层指数分布图的动态变化来看，也说明了城市化进程中城镇建筑和硬化的路面的增多导致了热岛强度的增强。     

Turbulent fluxes over inhomogeneous landscape

Mesoscale surface turbulent fluxes over a complex terrain surrounded by oceans have been investigated using a 3-D numerical mesoscale model, under conditions with and without synoptic flows. The study indicated that under synoptically calm condition, the allocation and intensity of mesoscale surface turbulent fluxes (MSTFs) were greatly impacted by the thermally forced mesoscale circulation (TFMC) over mesoscale heterogeneous landscape. The max-imum values of sensible (Hs) and latent (LE) heat fluxes were located over the convergent zones and considerably im-pacted by the soil wetness (M), but did not depend strongly on the atmospheric background thermal stability (β0). The simulated results suggested that the sensible heat flux was closely proportional to the square of wind speed in the surface layer. By the action of synoptic flow, the allocation of LE was shifted to downwind, its intensity increased.     

Determination of places in the great Athens area where the heat island effect is observed

Summary The major Athens area is surrounded by high mountains to the north and the east and is influenced by the sea (Saronic Gulf) to the south. As a result of its topography, the city experiences significant variations in its ventilation patterns even over small distances. The main purpose of the present study is to define places in the major Athens area where the heat island effect occurs. Several important climatic parameters are examined in combination with the application of various statistical tests. From this research it is mainly observed that the central and western industrialized parts of the city of Athens develop the “urban” heat island effect intensely. Nevertheless, district variations as regards the heat island intensity can be found in some regions, located close to the city centre and eastward of it, characterized by thick vegetation of trees or by “open areas”. Moreover, in places near the sea the air temperatures are higher in the cold period of the year, not because of the urbanization but mainly due to the influence of the sea, which favors the maintenance of high air temperatures. Last but not least, the persistence of high air temperatures during the hot period of the year or low air temperatures in the cold period is mostly related to the synoptic weather conditions and it cannot reasonably be considered as an index for the heat island effect development. Received June 1, 2000 Revised August 6, 2001     

Urban Heat Island Circulation in Göteborg,Sweden

Summary The paper presents a study of the Urban Heat Island Circulation (UHIC) in Göteborg, Sweden. Observations and recordings have been carried out from 1981 to 1986 during winter nights with anticyclonic weather conditions. The UHIC develops in general at a large negative net radiation balance, when the heat island intensity is at least 2.5°C, the wind speed less than 3 m/s and the sky is clear. If the weather conditions are favourable the UHIC starts 4–6 hours after midnight and stops a few hours after sunrise. An increase in cloud cover during the late night will not prevent the development of the UHIC. The UHIC layer extends to 40–70 metres in the vertical direction and to 10–13 km in the horizontal direction. The UHIC layer is capped by an inversion and the flow is almost independent of the direction of the regional flow. The UHIC is of great importance for the concentrations of air pollutions in Göteborg, as it transports both polluted and clean air. The study is a part of a clean air programme in the Göteborg area.With 7 Figures     

Temporal variability of the Buenos Aires, Argentina, urban heat island

This paper describes the statistical characteristics and temporal variability of the urban heat island (UHI) intensity in Buenos Aires using 32-year surface meteorological data with 1-h time intervals. Seasonal analyses show that the UHI intensity is strongest during summer months and an “inverse” effect is found frequently during the afternoon hours of the same season. During winter, the UHI effect is in the minimal. The interannual trend and the seasonal variation of the UHI for the main synoptic hours for a longer record of 48?years are studied and associated to changes in meteorological factors as low-level circulation and cloud amount. Despite the population growth, it was found a negative trend in the nocturnal UHI intensity that could be explained by a decline of near clear-sky conditions, a negative trend in the calm frequencies and an increase in wind speed. Urban to rural temperature differences and rural temperatures are negatively correlated for diurnal and nocturnal hours both for annual and seasonal scales. This result is due to the lower interannual variability of urban temperatures in comparison to rural ones.     

武汉市城市热岛强度非对称性变化

利用武汉市区气象站及其周边4个县气象站1960-2005年的气温资料,计算了46 a及分时段的季节和年平均气温、平均最高和最低气温倾向率,城市热岛强度倾向率及其贡献率。结果表明：46 a来,城区和郊区的平均气温均以上升趋势为主,最低气温增幅最大,最高气温增幅最小,甚至下降;冬季增幅最快,夏季增幅最慢,甚至下降,这是第一类非对称性。 城市热岛效应也存在增强趋势,以年平均、最低和最高气温表示的城市热岛强度倾向率分别为0.235℃/10 a、0.425℃/10 a和0.034℃/10 a,热岛效应贡献率分别达到60.4%、67.7%和21.8%,这是第二类非对称性。 46 a来的增温和城市热岛强度加强主要是最近23 a快速增温所致,进入本世纪增温进一步加剧。 摘要 计算了武汉市气象站、周边4县气象站平均的1960～2005年间以及前后两半时段四季和年平均、最高、最低气温倾向率,城市热岛强度倾向率和贡献率。结果表明：1）46年来,城区和郊区的平均气温均以增趋势为主,平均气温倾向率为正,最低气温增幅最大,最高气温增幅最小甚至下降,冬季增幅最快,夏季增幅最慢甚至下降,这是第一类非对称性;2）城市热岛效应也存在增趋势,以年平均、最低、最高气温表示的城市热岛强度倾向率分别为0.235、0.425、0.034 ℃/10a,热岛效应贡献率分别达到60.4%、67.7%、21.8%,这是第二类非对称性,3）46年来的增温和城市热岛强度加强主要是后23年快速增温所致,前23年气温变化不明显。武汉市气象站气温资料严重地保留着城市化影响,建议尽快迁站。 关键词 城市热岛强度 最高气温 最低气温 非对称性变化     

Heat island intensity with different meteorological conditions in a medium-sized town: Szeged,Hungary

Summary An analysis of the effects of the townSzeged, Hungary, on minimum temperatures between 1978 and 1980 is presented. The characteristics of the urban heat island effect were examined by revelation of the relationships between heat island intensity and macrosynoptic types, cloudiness, wind speed as well as the combination of cloud amount and wind speed. Anticyclonic weather situations, little or no cloud coverage, and calm or slight wind were favourable for a strong development of the heat island effect. In the case of extreme heat islands the domination of anticyclonic weather types was almost absolute.With 4 Figures     

1951—2017年鞍山市气温变化特征及城市热岛变化

利用建站以来鞍山站和海城乡村站的一日四次观测数据和逐日平均、最低和最高气温资料,对1951—2017年鞍山市年、四季和各月平均气温和极端气温变化特征及其变率进行了分析,并对鞍山城市热岛变化进行探讨.结果表明:1951—2017年鞍山市年平均最低气温的递增趋势最强、平均气温次之、平均最高气温最弱,且均通过显著性检验.19...     

夜间城市大气边界层和气溶胶的相互作用

本文利用能量闭合的二维非线性、非定常模式，结合地面热量平衡方程，研究了夜间城市边界层和气溶胶的相互作用问题。结果表明:气溶胶在夜间对大气低层起保温作用，对大气上层起冷却作用；使大气低层稳定度减小，上层稳定度增加；此外，气溶胶还能够削弱贴地逆温强度。在正常城市气溶胶污染情况下，气溶胶对城市热岛强度影响不大，但可使城市热岛环流稍有增加。夜间城市边界层对气溶胶的反馈作用使大气下层气溶胶浓度减小，上层气溶胶浓度增加。上述部分结论得到了在天津取得的城市热岛观测资料的直接验证。     

Temperature trends through urbanization in Metropolitan Washington,D.C., 1945–1979

Summary Annual and seasonal changes of the urban heat island magnitude in Washington, D.C. and a close-in suburb were analyzed for the period of 1945 through 1979. Monthly and annual mean temperature data, corrected for elevation, from three stations (National Airport, D.C.—downtown, Silver Spring, MD—suburban, and Beltsville, MD—rural) were evaluated by testing the statistical significance of temperature differences between the different data sets.The analysis indicated that the absolute heat island magnitudes have increased at the rate of 0.020 and 0.019 C/yr at Washington National Airport and Silver Spring, respectively during the study period. The differences between these two rates were not statistically significant at the 0.95 confidence level. However, the increase of the heat island magnitude from 1945 to 1979 at the suburban station was 20% greater than that at the downtown station. Those results indicate that as urbanization progresses, the suburban site, Silver Spring, has become incorporated into the Washington, D.C. urban heat island. The data also indicate that the magnitude of the heat island near the city center has continued to increase despite a significant population decrease since 1950.With 5 Figures