Mesoscale aspects of the Urban Heat Island around New York City

Summary ?A mesoscale analysis of the Urban Heat Island (UHI) of New York City (NYC) is performed using a mesoscale network of weather stations. In all seasons the UHI switches on rapidly in late afternoon and shuts down even more rapidly shortly after dawn. It averages about 4 °C in summer and autumn and 3 °C in winter and spring. It is largest on nights with clear skies, low relative humidity through much of the troposphere, and weak northwest winds, when it may exceed 8 °C. The synoptic meteorological situation associated with the largest UHI occurs roughly two to three nights after cold front passages. During spring and summer, sea breezes commonly reduce and delay the UHI and displace it about 10 km to the west. Backdoor cold fronts, which occur most frequently in spring and early summer, reduce or even reverse the UHI, as cold air from the water to the northeast keeps NYC colder than the western suburbs. Cases documenting the sensitivity and rapidity of changes of the UHI to changes in parameters such as cloud cover, ceiling, and wind speed and direction are presented. Received August 16, 2001; revised October 6, 2002; accepted November 20, 2002 Published online March 17, 2003     

Large-Eddy Simulation of Mesoscale Circulations Forced by Inhomogeneous Urban Heat Island

The large-eddy simulation mode of the Weather Research and Forecasting model is employed to simulate the planetary boundary-layer characteristics and mesoscale circulations forced by an ideal urban heat island (UHI). In our simulations, the horizontal heterogeneity of the UHI intensity distribution in urban areas is considered and idealized as a cosine function. Results indicate that the UHI heating rate and the UHI intensity heterogeneity affect directly the spatial distribution of the wind field; a stronger UHI intensity produces a maximum horizontal wind speed closer to the urban centre. The strong advection of warm air from the urban area to the rural area in the upper part of the planetary boundary-layer causes a more stable atmospheric stratification over both the urban and rural areas. The mesoscale sensible heat flux caused by the UHI circulation increases with UHI intensity but vanishes when the background wind speed is sufficiently high $(>$ 3.0  $\mathrm{{m\,s}}^{-1})$ .     

Some meteorological aspects of air pollution in Athens,Greece

Summary The purpose of this paper is to examine some meteorological aspects of air pollution in the Athens area, Greece. Over recent years much attention has been directed to the importance of spells of weather in providing conditions that give rise to inversion of temperature at or near ground level, and hence to risks of severe incidents of air pollution. So, emphasis is given to the importance of anticyclonic conditions, associated with pronounced stability during ground level radiation inversions, when the same sampling sites show high concentration of both SO₂ and smoke. Fifteen years of surface and radiosonde data obtained from Hellinikon Airport Athens are used for a climatological base. The meteorology of high concentration episodes has also been examined and the synoptic characteristics for the onset and end of such episodes have been identified. Finally, trends of pollution episodes and calculation of an air stagnation index for Athens have been obtained, which give a predicting indication about the occurrence of high pollution concentration.With 11 Figures     

城市台站周边热岛效应和土地利用与覆盖变化关系

以合肥市气象站为中心,利用1990～2006年的Landsat TM影像,获取不同半径圆形缓冲区范围内下垫面土地分类信息以及对应年份的气温年均值、极值、日定时数据资料,分析了下垫面各土地类型及其变化和站点周边热岛效应的关系.分析得出:城市热岛与建设用地有着最强正相关,与林草地和耕地有着显著负相关,与夜晚水体有着较强正相关.下垫面类型对城市热岛的影响随着每天的不同时刻而变化.4种下垫面类型对城市热岛的影响范围上,建设用地一般在6km以内、林草地4km以内、耕地在4km时最显著,水体则随着距离的增加,其影响范围缓慢上升到8 km.同时,通过分析土地利用年变化和城市热岛效应变化的关系,进一步验证了城市发展对城市热岛效应起着至关重要的作用.最高温和14时(北京时间)热岛强度年变化与土地利用年变化有着较强的相关性.另外,迁站后热岛效应明显减弱.最后,重点探讨了下垫面类型和热岛效应关系的可能原因.     

Moscow Urban Heat Island: Detection,boundaries, and variability

The determination of the anthropogenic impact on the thermal regime of a megalopolis is discussed. The nominal boundaries of the megalopolis thermal effects are determined taking into account orographic and landscape effects and the variability of temperature difference between the center of the city and its suburbs. It is proposed to use the data of stations located within 40-50 km from the urban agglomeration boundaries for calculating the anthropogenic component of the urban heat island. The parameters of the heat island in Moscow are determined from the measurement data on maximum and minimum daily surface air temperature in 2012-2016, and their significant seasonal and intradaily variability is revealed. It is corroborated that anthropogenic causes for the higher air temperature in Moscow as compared with suburbs during the cold season are the release and loss of heat of heating systems; in the absence of snow cover the anthropogenic effect of these sources is enhanced by the thermal radiation of the urban surface.     

城市热岛效应研究概况

随着我国城市化进程的不断加快,城市中的环境污染问题也日益严重,表现为城市比周围非城市化地区的地表和大气温度要高的热岛效应作为这些环境问题中的典型代表有着重要的研究意义。近几十年来国内外的有关专家从微观及宏观层面上对城市热岛效应的产生原因、造成影响、变化规律、缓解措施等方面进行了一系列的研究与探索。由于城市测点有限,过去的研究尚不能全面反映出研究区热岛效应。遥感科学和技术的发展,为城市热岛效应的研究提供了有利条件。本文介绍了热红外遥感技术在热岛研究中的应用及城市规划对城市热岛效应的影响,并展望了该领域的发展前景。     

城市热岛效应研究概况

随着我国城市化进程的不断加快,城市中的环境污染问题也日益严重,表现为城市比周围非城市化地区的地表和大气温度要高的热岛效应作为这些环境问题中的典型代表有着重要的研究意义。近几十年来国内外的有关专家从微观及宏观层面上对城市热岛效应的产生原因、造成影响、变化规律、缓解措施等方面进行了一系列的研究与探索。由于城市测点有限,过去的研究尚不能全面反映出研究区热岛效应。遥感科学和技术的发展,为城市热岛效应的研究提供了有利条件。本文介绍了热红外遥感技术在热岛研究中的应用及城市规划对城市热岛效应的影响,并展望了该领域的发展前景。     

The Urban Heat Island Effect at Fairbanks, Alaska

Summary  Using climatic data from Fairbanks and rurally situated Eielson Air Force Base in Interior Alaska, the growth of the Fairbanks heat island was studied for the time period 1949 – 1997. The climate records were examined to distinguish between a general warming trend and the changes due to an increasing heat island effect. Over the 49-year period, the population of Fairbanks grew by more than 500%, while the population of Eielson remained relatively constant. The mean annual heat island observed at the Fairbanks International Airport grew by 0.4 °C, with the winter months experiencing a more significant increase of 1.0 °C. Primary focus was directed toward long-term heat island characterization based on season, wind speed, cloud cover, and time of day. In all cases, the minima temperatures were affected more than maxima and periods of calm or low wind speeds, clear winter sky conditions, and nighttime exhibited the largest heat island effects. Received August 17, 1998 Revised March 26, 1999     

Analysis of the long-term precipitation series at Athens,Greece

In this paper, the characteristics of the long-term precipitation series at Athens (1858–1985) have been statistically analyzed. This study covers both the history and the analysis of the data. The ten-year mean amounts, the monthly and annual amounts averaged over the intervals 1858–1890, 1891–1985, 1951–1980, 1858–1985, the mean number of hours of precipitation and the precipitation intensity are given. The analysis of long-term time series of climatic data (in particular precipitation) is a useful tool for the study of past climate. Different statistical techniques are used in order to depict monthly, seasonal and annual variations, as well as trends, periodicities and recurrence intervals of the amount, intensity and number of precipitation days. The analysis reveals many interesting characteristics. These characteristics of the precipitation regime are extended to a time scale from seasonal variation to a semi-secular trend. The study of such long-term series may be helpful not only in practical applications of rainfall, but also for explaining the possible physical or anthropogenic mechanisms of climatic fluctuations and tendencies. The series of precipitation at Athens is one of the longest in south-eastern Europe.     

热岛效应对四季变化的影响

以具有明显热岛效应的城区气温来划分的四季只能代表城区,划分郊外的四季时应剔除各时段的城市热岛效应值,剔除各时段的城市热岛效应值后计算出来的四季既在一定程度上反映了全球变暖的影响,又具有较好的连续性。     

热岛效应对四季变化的影响

以具有明显热岛效应的城区气温来划分的四季只能代表城区,划分郊外的四季时应剔除各时段的城市热岛效应值,剔除各时段的城市热岛效应值后计算出来的四季既在一定程度上反映了全球变暖的影响,又具有较好的连续性.     

深圳的城市热岛效应

通过全球气候增暖和深圳气象台气温急升等事实，探索因观测环境急剧改变而又缺乏对比观测时，台站所在地城市化后的增温及“热岛效应”等情况。从而得出气候增暖和城市热岛效应场具有较明显的季节性；具有明显的昼夜差别，且晚间远比白天明显。     

城市热岛效应监测方法研究进展

城市热岛效应是一种由于城市建筑及人们活动导致的热量在城区空间范围内聚集的现象,是城市气候最明显的特征之一.由于城市热岛影响因素以及相互关系的复杂性,为了精确细致地描述其时空分布,人们采用了多种方法来研究城市热岛现象,主要归纳为：气象站法、定点观测法、运动样带法、遥感测定法以及模拟预测等.最后,认为各种测定方法都存在一定的缺陷,建议多种测定方法综合运用.     

Variability of the Linke and Unsworth-Monteith turbidity parameters in Athens, Greece

Summary  This work studies the variability of the Linke (T _L ) and Unsworth-Monteith (T _U ) turbidity parameters in the urban atmosphere of Athens. Beam irradiance observations performed at the Actinometric Station of the National Observatory of Athens are used in the period 1975–1995. This study examines (i) the inter-annual variation of T _L and T _U , (ii) their mean seasonal variability, (iii) their monthly average variation, and (iv) their mean daily variation. Also, for various air-mass origins, the mean seasonal variations of T _L and T _U are given. The frequency of occurrence of the parameters in various ranges is also shown. An innovative interpretation of the impact of the Saharan dust on the radiative properties in the atmosphere of Athens is attempted. Received May 19, 2000 Revised October 17, 2000     

Temporal variations of atmospheric tides over Athens,Greece

Summary The mean daily march of pressure (hourly values) for each month of the 96 year period 1894–1989 in Athens, Greece is studied using Fourier analysis. The annual variation of the harmonic parameters (amplitude, time of maximum,x andy-components) is examined. The globally excited 2nd and 3rd harmonics show in general the same behaviour as in other places of the Earth. Similar features show the corresponding parameters of the daily solar radiation march. The first harmonic displays some local characteristics. The long period fluctuations study revealed statistically significant trends in most parameters of the 2nd harmonic, most strikingly the 0.5 h shift in the time of its maximum during the 20th century. Power spectrum analysis showed the existence of a biennial oscillation inB ₁, thex-component of the first harmonic, but this oscillation is mainly confined to the second half of the entire period. A periodicity of about 6 years which could be associated to the Southern Oscillation was also found inB ₁ while inA ₁, they-component, a periodicity close to the 11-year solar cycle and another one close to the nutation of the Earth's axis are present. The lunar tides are too small to be detected by the same methods. However the semilunar tide was revealed to be 10–20 times smaller than the semisolar.With 8 Figures     

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     

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     

昆明地区城市热岛效应的再分析

在对地面气温资料进行均一性检验和订正的基础上,分析了1971—2008年昆明地区(包括城区、郊县和太华山)气温序列的变化趋势,研究了城市化对气温序列的可能影响,揭示了在城市化快速推进和低纬高原复杂地形条件下城市热岛效应的特殊性和复杂性。结果表明,昆明地区的平均气温总体呈上升趋势,上升速率大小依次为昆明城区>郊县>太华山。其中,昆明城区和郊县气温具有相似的变化规律,主要表现为冬、春季最低气温显著升高和气温日较差明显减小;太华山气温的变化则明显不同,主要表现为最低气温全年少变,冬、秋季最高气温小幅上升,而气温日较差有增大趋势。20世纪80年代中后期以来,昆明城区与郊县气温,特别是最低气温的显著上升可能受到城市化的严重影响,因此以往以郊县为对比乡村站的研究在很大程度上低估了城市化对昆明气温序列的影响。而在此之前,昆明最低和最高气温均会因对比乡村站选取的不同而表现出"城市冷岛"特征。     

南京城市热岛效应研究

利用4个气象站1961～2005年气温资料,对南京市的城市热岛效应进行了全面、细致的研究。结果表明：1）平均而言,南京市的热岛强度基本在0.5 ℃左右,热岛强度的高值体现在最低气温上,极端情况可能达到6 ℃左右;2）南京城市热岛效应具有明显的季节变化和日变化特征,夏半年要强于冬半年,夜间强于白天;3）随着城市规模的发展,南京市的城市热岛效应为增强趋势,用年平均气温计算获得的热岛强度增幅为0.109 ℃·(10 a)-1。     

绵阳城市热岛效应分析

本文首先采用模糊c-均值聚类法和剔除法,筛选出用于计算绵阳城市热岛强度的10个城市站和15个郊区站,然后利用这25个自动气象站的逐时气温资料,分析2018年绵阳城市热岛效应不同时间尺度的变化特征。结果表明:2018年绵阳存在城市热岛效应,平均热岛强度为0.64℃,表现为弱热岛等级;四季热岛效应冬季最强,其次是春季,夏季和秋季相当;逐月热岛强度3月最大、7月最小;绵阳城市热岛效应存在明显的日变化,热岛强度夜间大于白天,日最大热岛强度几乎均出现在晚上。