urban heat island cluj
125499899
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.
Theoretical and Applied Climatology
Ioana Herbel Adina Croitoru Adina Viorica Rus Cristina Florina Rosca Gabriela Victoria Harpa Antoniu-Flavius Ciupertea I Rus
133414347
Detection of atmospheric urban heat island through direct measurements in Cluj Napoca city, Romania
In the last decades, cities worldwide have experienced accelerated development, so that continuous urbanization and its impact is presently one of the most important topics in diff erent fi elds of research. The main aim of this study is to identify the intensity of the atmospheric urban heat island in Cluj Napoca city, through direct observations campaigns by using fi xed points and transect measurements. The data has been collected over a period of 6 months (May October 2015) The measurements have been performed mainly in anti cyclonic weather condition, during the night, between 23:00 and 03:00. The profi les trajectories followed the main roads of the city on directions North South, East West, and Northwest Southeast. 8 fi xed points have been chosen in order to highlight best the temperature patt erns in diff erent Local Climate Zones (LCZs) The main fi ndings of the study are the followings: the direct observations performed in three seasons (spring, summer and autumn) revealed the existence of an atmospheric urban heat island in Cluj Napoca city; the warmest areas are compact high rise and compact midrise, located in the eastern half of the city, where the temperature increases by more than 2.0 degC, as average value for all campaigns, but the maximum values, recorded in the summer are higher than 3.0 degC; the coolest areas are sparsely built areas and the large low rise/water areas, where the temperature is quite similar to that recorded in the nearby rural areas (diff erence of 0.0 0.1 degC, as average values) local factors, such as mountain breeze and topography have a great impact on the atmospheric urban heat island confi guration.
Ioana Herbel Adina Croitoru I Rus Gabriela Victoria Harpa Antoniu-Flavius Ciupertea
130585432
URBAN HEAT ISLAND DETECTION BY INTEGRATING SATELLITE IMAGE DATA AND GIS TECHNIQUES. CASE STUDY: CLUJ NAPOCA CITY, ROMANIA
Alexandru Mircea Imbroane
209778099
Influences of urban spatial form on urban heat island effects at the community level in China
Abstract Owing to increasing population densities and impervious surface areas, heat island effects increasingly dominate urban environments and hinder sustainable development. The urban spatial form plays an important role in mitigating urban heat islands. Taking Ganjingzi District, Dalian, as an example, this study considered urban spatial form at the community scale using spatial autocorrelation and spatial regression methods to explore 2003 2018 spatial and temporal differentiation characteristics and driving factors of Land Surface Temperature (LST) The LST of each community showed a gradually increasing trend; high values >30degC) were concentrated in central and eastern areas; low values were
Andong Guo Jun Yang Xiangming Xiao Jianhong Xia (Cecilia) Cui Jin Xueming Li
208831826
Recent progress on urban overheating and heat island research. Integrated assessment of the energy, environmental, vulnerability and health impact. Synergies with the global climate change
Abstract Urban overheating is documented for more than 400 major cities in the world. Numerous experimental data show that the magnitude of the average temperature increase may exceed 4 5 C, while at the peak may exceed 10 C. Increased ambient temperatures cause a serious impact on the cooling energy consumption, peak electricity demand, heat related mortality and morbidity, urban environmental quality, local vulnerability and comfort. Synergies between urban heat island and heat waves increase further the amplitude of urban overheating The present paper reviews and reports the recent progress and knowledge on the specific impact of current and projected urban overheating in energy, peak electricity demand, air quality, mortality and morbidity and urban vulnerability. In parallel, it discusses new findings related to the characteristics and the magnitude of urban overheating, and reports and analyse the recent knowledge on the synergies between urban heat island and heat waves.
Energy and Buildings
Mathew Santamouris
117402668
Urban heat island impacts on building energy consumption: A review of approaches and findings
Urban heat island (UHI) could have significant impacts on building energy consumption by increasing space cooling demand and decreasing space heating demand. However, the impacts of UHI on building energy consumption were understudied due to challenges associated with quantifying UHI induced temperature change and evaluating building energy consumption. In this study, we reviewed existing literature for improving the understanding of UHI impacts on building energy consumption. It was found that UHI could result in a median increase of 19.0% in cooling energy consumption and a median decrease of 18.7% in heating energy consumption. The reported UHI impacts showed strong intercity variations with an increase of cooling energy consumption from 10% to 120% and a decrease of heating energy consumption from 3% to 45% The UHI impacts also showed clear intra city variations with stronger impacts in urban center than that in urban periphery. There were significant differences in the method and the data used to evaluate the UHI impacts in previous studies. Four future research focuses were recommended to better understand the UHI impacts on building energy consumption.
Energy
Xiaoma Li Yuyu Zhou Sha Yu Gensuo Jia Huidong Li Wenliang Li
195415615
Towards the next generation of green building for urban heat island mitigation: Zero UHI impact building
Abstract At present, cities are under the threats of global warming and urban heat island (UHI) phenomenon, where buildings are an important cause and also the sufferer of urban overheating. Therefore, building, especially the green building (GB) is predominantly provisioned to address the increasing energy consumption and carbon emissions in response to climate change, while to our best knowledge, it has been scarcely requested for UHI mitigation (UHIM) Therefore, this paper proposes the concept of GB based UHIM system, or 'zero UHI impact building' or 'zero heat building' or 'microclimate neutral building' aiming to achieve the zero heat impact on surrounding environments through reasonably designing and operating buildings, or depending on innovative techniques to eliminate the excessive heats, on the basis of GB's goals. In specific, this paper defines the boundary of the GB based UHIM system, analyzes the interactions between building and urban heat fluxes, and the factors that may affect the use of UHIM techniques on building components. The potentials to establish the GB based UHIM system are further analyzed in aspects of the UHI impacts on the GB benefits and the principle for heat mitigation. Moreover, the pathway to GB based UHIM system implementation is further elaborated and suggestions for future direction and work are given. Overall, this paper presents the theoretical and practical foundation for the establishment of GB based UHIM system and it is a significant move of building sector in response to the temperature increase.
Sustainable Cities and Society
Bao-jie He
53759738
The footprint of urban heat island effect in 302 Chinese cities: Temporal trends and associated factors.
The urban heat island (UHI) effect has been a concern for decades due its adverse influence on energy consumption, air and water quality, and, most importantly, the health of urban dwellers. Researchers have paid much attention to the magnitude of the UHI effect, but ignored its spatial extent (i.e. footprint) which is another important aspect of the UHI effect. In this study, we systematically analyzed the footprint of surface UHI (SUHI) effect in 302 Chinese cities, especially temporal trends of the footprint, by using multi source remote sensing data. The footprint of SUHI effect (FP) was estimated by the Gaussian surface, and its temporal trend was examined by the Mann Kendal and the Sen's slope estimator non parametric tests. We found the FP showed evident diurnal (daytime nighttime) seasonal (summer winter) and inter city (big cities small and medium sized cities) differences. During the period 2003 2016, over 80% of the 302 cities exhibited increasing trends of the FP in annual days and summer days, and the increasing trends were statistically significant (p 0.05) in about half of these cities. In the nights, the FP increased in more than 70% of the cities, and about one third of the 302 cities experienced significantly increasing trends of the FP. On average, the annual daytime and annual nighttime FPs increased at a rate of 5.0% per year and 3.8% per year, respectively. More importantly, the correlation analysis indicated that the increase of anthropogenic heat emissions and the decrease of vegetation activities and surface albedos should take lead responsibility for the expansion of the FP in the urbanization process. These results reveal that the spatial extent of heat island effect has expanded significantly in numerous Chinese cities, and this increasing trend will be sustained in the coming years if no more effective measures are carried out.
The Science of the total environment
Qiquan Yang Xin Huang Qiuhong Tang
53112996
Quantifying urban heat island intensity and its physical mechanism using WRF/UCM.
Reliable quantification of urban heat island intensity (UHII) is crucial for the evaluation of extreme heat waves and the related heat stress. As a powerful approach for the study of urban climate, numerical models can simulate urban heat island (UHI) in both high spatial and temporal resolutions. However, accurate quantification of UHII using modelling grid data is still a challenge at present, due to the different criterions for the selection of urban/rural grids. This study simulates the high resolution UHI in the city of Berlin using the Weather Research and Forecasting Model coupled with Urban Canopy Module. A new method to quantify UHII, which is based on the fitted linear functions of simulated 2 m air temperature (T2m) using the impervious surface area in WRF grids (ISAWRF) was adopted and evaluated. The simulated T2m matches the observations well, with a correlation coefficient of 0.95 (P 0.01) and RMSE of 1.76 degC. The study area shows a strong UHI at nighttime. The simulated nighttime T2m increases with the increase in the ISAWRF. The linear functions of simulated nighttime T2m against ISAWRF are well fitted. The UHII is calculated as the products of the slopes of fitted functions and the largest ISAWRF. The derived UHII shows U shaped diurnal variations, with high values at nighttime. The difference of simulated surface temperature and sensible heat flux between the impervious surface and the vegetation surface jointly determines the derived UHII. The large difference of surface temperature and the small difference of sensible heat flux between the impervious and the vegetation surface generate the high UHII at nighttime and vice versa during the daytime. The method of ISAWRF based function of T2m overcomes the problems of traditional methods in arbitrary selecting urban/rural grids. It can be used easily to quantify UHII and to do the comparison study of UHII between different cities.
The Science of the total environment
Huidong Li Yuyu Zhou Xun Wang Xu Zhou Huiwen Zhang Sahar Sodoudi
93003477
Urban heat island: Aerodynamics or imperviousness?
Vegetation and moisture play the most important roles in controlling daytime urban heat islands and their spatial variability. More than half of the world's population now live in cities, which are known to be heat islands. While daytime urban heat islands (UHIs) are traditionally thought to be the consequence of less evaporative cooling in cities, recent work sparks new debate, showing that geographic variations of daytime UHI intensity were largely explained by variations in the efficiency with which urban and rural areas convect heat from the land surface to the lower atmosphere. Here, we reconcile this debate by demonstrating that the difference between the recent finding and the traditional paradigm can be explained by the difference in the attribution methods. Using a new attribution method, we find that spatial variations of daytime UHI intensity are more controlled by variations in the capacity of urban and rural areas to evaporate water, suggesting that strategies enhancing the evaporation capability such as green infrastructure are effective ways to mitigate urban heat.
Science Advances
Dan Li Weilin Liao Angela J Rigden Xiaoping Liu Dagang Wang Sergey Malyshev Elena Shevliakova