scholarly journals Comparison of Temperatures and Spatial Resolutions between Urban Sensors and National Weather Observations (ASOS, AWS) for Urban Heat Island Intensity Analysis

2021 ◽  
Vol 21 (3) ◽  
pp. 39-48
Author(s):  
Haekyung Park
Keyword(s):  
Urban Heat Island ◽  
Urban Environments ◽  
Sensor Data ◽  
Heat Island ◽  
Heat Islands ◽  
The Public ◽  
Weather Observations ◽  
Urban Heat ◽  
The Difference ◽  
Weather Observation

Urban temperatures have become more important because the frequency and intensity of heatwaves will increase with the worsening urban heat island effects due to climate change. Recently, urban sensors are emerging as a new means of heat island analysis, and urban sensor data including temperatures were opened to the public in Seoul in 2020. However, there are insufficient cases of analysis and the differences from national weather observation are unknown. Accordingly, this study introduces the S⋅DoT (Smart Seoul Data of Things), an urban sensor in Seoul, and compared S⋅DoT temperatures with national weather observation (such as ASOS and AWS) temperature in order to facilitate heat island analysis using urban sensors. The result shows the S⋅DoT temperature is about 1-1.15 ℃ higher than ASOS⋅AWS during May to August 2020, which is due to differences in the height and installation environment, not in the performance of the equipment. S⋅DoT is installed in the urban environments at the height of approximately 3 m and measures the actual living temperature, whereas ASOS measures temperature in the controlled environment and AWS measures temperature from the higher position due to being installed on the top of a building. Therefore, we suggest that when using S⋅DoT together with rural AWS temperature to analyze the intensity of heat islands, calibration should be considered taking into account the difference between the two observations, and a better method is to calculate the heat island intensity only using S⋅DoT temperature in urbanized and non-urbanized areas without using rural temperature.

scholarly journals Urban heat island in Bloemfontein during winter

2013 ◽  
Vol 32 (1) ◽  
Author(s):  
Pieter Snyman ◽  
A. Stephen Steyn
Keyword(s):  
Maximum Intensity ◽  
Urban Heat Islands ◽  
Urban Air ◽  
Heat Island ◽  
Heat Islands ◽  
Air Temperatures ◽  
Local Topography ◽  
Urban Heat ◽  
The Difference ◽  
The City

Urban heat islands (UHIs) are characterised by warmer urban air temperatures compared to rural air temperatures, and the intensity is equal to the difference between the two. Air temperatures are measured at various sites across the city of Bloemfontein and then analysed to determine the UHI characteristics. The UHI is found to have a horseshoe shape and reaches a maximum intensity of 8.2 °C at 22:00. The UHI is largely affected by the local topography.

Urban heat island estimation from improved selection of urban and rural stations by DTW algorithm

2021 ◽  
Author(s):  
Yonghong Hu ◽  
Gensuo Jia ◽  
Jinlong Ai ◽  
Yong Zhang ◽  
Meiting Hou ◽  
...  
Keyword(s):  
Urban Heat Island ◽  
Urban Climate ◽  
Global Scale ◽  
Heat Island ◽  
Climate Effect ◽  
Urban Heat ◽  
The Difference ◽  
Temperature Records ◽  
Dynamic Time ◽  
Selection Of

Abstract Typical urban and rural temperature records are essential for the estimation and comparison of urban heat island effects in different regions, and the key issues are how to identify the typical urban and rural stations. This study tried to analyze the similarity of air temperature sequences by using dynamic time warping algorithm (DTW) to improve the selection of typical stations. We examined the similarity of temperature sequences of 20 stations in Beijing and validated by remote sensing, and the results indicated that DTW algorithm could identify the difference of temperature sequence, and clearly divide them into different groups according to their probability distribution information. The analysis for station pairs with high similarity could provide appropriate classification for typical urban stations (FT, SY, HD, TZ, CY, CP, MTG, BJ, SJS, DX, FS) and typical rural stations (ZT, SDZ, XYL) in Beijing. We also found that some traditional rural stations can’t represent temperature variation in rural surface because of their surrounding environments highly modified by urbanization process in last decades, and they may underestimate the urban climate effect by 1.24℃. DTW algorithm is simple in analysis and application for temperature sequences, and has good potentials in improving urban heat island estimation in regional or global scale by selecting more appropriate temperature records.

scholarly journals Influence of Weather Factors on Thermal Comfort in Subtropical Urban Environments

2020 ◽  
Vol 12 (5) ◽  
pp. 2001 ◽  
Author(s):  
Chih-Hong Huang ◽  
Hsin-Hua Tsai ◽  
Hung-chen Chen
Keyword(s):  
Thermal Comfort ◽  
Urban Heat Island ◽  
Thermal Environment ◽  
Urban Environments ◽  
Heat Island ◽  
Weather Factors ◽  
Urban Forms ◽  
Thermal Environments ◽  
Island Effect ◽  
Urban Heat

Urbanization has influenced the distribution of heat in urban environments. The mutual influence between weather factors and urban forms created by dense buildings intensify human perception of the deteriorating thermal environment in subtropics. Past studies have used real-world measurements and theoretical simulations to understand the relationship between climate factors and the urban heat island effect. However, few studies have examined how weather factors and urban forms are connected to the thermal environment. To understand the influence of various weather factors on urban thermal environments in various urban forms, this study applied structural equation modeling to assumptions of linear relationships and used quantitative statistical analysis of weather data as well as structural conversion of this data to establish the structural relationships between variables. Our objective was to examine the relationships among urban forms, weather factors, and thermal comfort. Our results indicate that weather factors do indeed exert influence on thermal comfort in urban environments. In addition, the thermal comfort of urban thermal environments varies with location and building density. In hot and humid environments in the subtropics, humidity and wind speed have an even more profound impact on the thermal environment. Apparent temperature can be used to examine differences in thermal comfort and urban forms. This study also proved that an urban wind field can effectively mitigate the urban heat island effect. Ventilation driven by wind and thermal buoyancy can dissipate heat islands and take the heat away from urban areas.

scholarly journals Effect of Land Cover Fractions on Changes in Surface Urban Heat Islands Using Landsat Time-Series Images

2019 ◽  
Vol 16 (6) ◽  
pp. 971 ◽  
Author(s):  
Tao Chen ◽  
Anchang Sun ◽  
Ruiqing Niu
Keyword(s):  
Land Cover ◽  
Urban Heat Island ◽  
Land Surface ◽  
Urban Heat Islands ◽  
Urban Heat Island Intensity ◽  
Heat Island ◽  
Impervious Surfaces ◽  
Heat Islands ◽  
Urban Heat ◽  
Surface Urban Heat Island

Man-made materials now cover a dominant proportion of urban areas, and such conditions not only change the absorption of solar radiation, but also the allocation of the solar radiation and cause the surface urban heat island effect, which is considered a serious problem associated with the deterioration of urban environments. Although numerous studies have been performed on surface urban heat islands, only a few have focused on the effect of land cover changes on surface urban heat islands over a long time period. Using six Landsat image scenes of the Metropolitan Development Area of Wuhan, our experiment (1) applied a mapping method for normalized land surface temperatures with three land cover fractions, which were impervious surfaces, non-chlorophyllous vegetation and soil and vegetation fractions, and (2) performed a fitting analysis of fierce change areas in the surface urban heat island intensity based on a time trajectory. Thematic thermal maps were drawn to analyze the distribution of and variations in the surface urban heat island in the study area. A Multiple Endmember Spectral Mixture Analysis was used to extract the land cover fraction information. Then, six ternary triangle contour graphics were drawn based on the land surface temperature and land cover fraction information. A time trajectory was created to summarize the changing characteristics of the surface urban heat island intensity. A fitting analysis was conducted for areas showing fierce changes in the urban heat intensity. Our results revealed that impervious surfaces had the largest impacts on surface urban heat island intensity, followed by the non-chlorophyllous vegetation and soil fraction. Moreover, the results indicated that the vegetation fraction can alleviate the occurrence of surface urban heat islands. These results reveal the impact of the land cover fractions on surface urban heat islands. Urban expansion generates impervious artificial objects that replace pervious natural objects, which causes an increase in land surface temperature and results in a surface urban heat island.

scholarly journals A Spatio-Temporal Bayesian Model for Estimating the Effects of Land Use Change on Urban Heat Island

2019 ◽  
Vol 8 (12) ◽  
pp. 522 ◽  
Author(s):  
Xin Liu ◽  
Zuolin Xiao ◽  
Rui Liu
Keyword(s):  
Land Use ◽  
Urban Heat Island ◽  
Southwest China ◽  
Regional Scale ◽  
Heat Island ◽  
Bayesian Hierarchical ◽  
Temporal Autocorrelation ◽  
Urban Heat ◽  
Spatio Temporal ◽  
The Difference

The urban heat island (UHI) phenomenon has been identified and studied for over two centuries. As one of the most important factors, land use, in terms of both composition and configuration, strongly influences the UHI. As a result of the availability of detailed data, the modeling of the residual spatio-temporal autocorrelation of UHI, which remains after the land use effects have been removed, becomes possible. In this study, this key statistical problem is tackled by a spatio-temporal Bayesian hierarchical model (BHM). As one of the hottest areas in China, southwest China is chosen as our study area. Results from this study show that the difference of UHI levels between different cities in southwest China becomes large from 2000 to 2015. The variation of the UHI level is dominantly driven by temporal autocorrelation, rather than spatial autocorrelation. Compared with the composition of land use, the configuration has relatively minor influence upon UHI, due to the terrain in the study area. Furthermore, among all land use types, the water body is the most important UHI mitigation factor at the regional scale.

Emergence of opposite trends in daytime and night-time urban heat island intensities in England

2020 ◽  
Author(s):  
Eunice Lo ◽  
Dann Mitchell ◽  
Sylvia Bohnenstengel ◽  
Mat Collins ◽  
Ed Hawkins ◽  
...  
Keyword(s):  
Urban Heat Island ◽  
Urban Areas ◽  
Urban Land Use ◽  
Urban Heat Islands ◽  
Urban Heat Island Effect ◽  
Heat Island ◽  
Night Time ◽  
Heat Islands ◽  
Island Effect ◽  
Urban Heat

<p>Urban environments are known to be warmer than their sub-urban or rural surroundings, particularly at night. In summer, urban heat islands exacerbate the occurrence of extreme heat events, posing health risks to urban residents. In the UK where 90% of the population is projected to live in urban areas by 2050, projecting changes in urban heat islands in a warming climate is essential to adaptation and urban planning.</p><p>With the use of the new UK Climate Projections (UKCP18) in which urban land use is constant, I will show that both summer urban and sub-urban temperatures are projected to increase in the 10 most populous built-up areas in England between 1980 and 2080. However, differential warming rates in urban and sub-urban areas, and during day and at night suggest a trend towards a reduced daytime urban heat island effect but an enhanced night-time urban heat island effect. These changes in urban heat islands have implications on thermal comfort and local atmospheric circulations that impact the dispersion of air pollutants. I will further demonstrate that the opposite trends in daytime and night-time urban heat island effects are projected to emerge from current variability in more than half of the studied cities below a global mean warming of 3°C above pre-industrial levels.</p>

scholarly journals Evaporation from water surfaces in urban environments, using Prague and Pilsen (Czech Republic) as examples

2016 ◽  
Vol 4 (4) ◽  
pp. 13-23
Author(s):  
Gražyna Knozová ◽  
Jáchym Brzezina ◽  
Jaroslav Rožnovský ◽  
Mojmír Kohut
Keyword(s):  
Thermal Conditions ◽  
Local Scale ◽  
Urban Environments ◽  
Heat Island ◽  
Two Cities ◽  
Water Surfaces ◽  
Urban Heat ◽  
The Subject ◽  
The Difference ◽  
Rate Of Evaporation

AbstractThe subject of this study is an evaluation of the amount of evaporation from water surfaces (VVH), measured using EWM devices in two cities of different sizes, and located approximately 80 km from each other – Prague and Pilsen. The results were analyzed in the context of urban phenomena, which are pronounced especially in Prague, and also in the context of meteorological and morphological conditions in those locations. It was found that higher amounts of evaporation were measured at the meteorological station in Pilsen. The difference between the average sum of VVH per season (1st May to 30th September) between 2005 and 2014 for the two locations is 33.3 mm. The difference between daily average values was 0.2 mm. Given the suburban nature of the two locations where measurements were taken, it was not possible to draw any conclusions about the effect of the urban heat island on the rate of evaporation and values of VVH. Factors significantly influencing VVH are surface roughness, which is higher in urban environments than in open landscapes. Based on the results it was concluded that at both a regional and a local scale, the rate of evaporation is more affected by wind speed than thermal conditions. The measured VVH values differ, not just because of the urban dimension of the two cities compared, but especially as a result of different topoclimatic location of the two stations.

scholarly journals Quantification of Urban Heat Island-Induced Contribution to Advance in Spring Phenology: A Case Study in Hangzhou, China

2021 ◽  
Vol 13 (18) ◽  
pp. 3684
Author(s):  
Yingying Ji ◽  
Jiaxin Jin ◽  
Wenfeng Zhan ◽  
Fengsheng Guo ◽  
Tao Yan
Keyword(s):  
Surface Temperature ◽  
Urban Heat Island ◽  
Land Surface Temperature ◽  
Land Surface ◽  
Urban Areas ◽  
Vegetation Index ◽  
Heat Island ◽  
Spring Phenology ◽  
Urban Heat ◽  
The Difference

Plant phenology is one of the key regulators of ecosystem processes, which are sensitive to environmental change. The acceleration of urbanization in recent years has produced substantial impacts on vegetation phenology over urban areas, such as the local warming induced by the urban heat island effect. However, quantitative contributions of the difference of land surface temperature (LST) between urban and rural (ΔLST) and other factors to the difference of spring phenology (i.e., the start of growing season, SOS) between urban and rural (ΔSOS) were rarely reported. Therefore, the objective of this study is to explore impacts of urbanization on SOS and distinguish corresponding contributions. Using Hangzhou, a typical subtropical metropolis, as the study area, vegetation index-based phenology data (MCD12Q2 and MYD13Q1 EVI) and land surface temperature data (MYD11A2 LST) from 2006–2018 were adopted to analyze the urban–rural gradient in phenology characteristics through buffers. Furthermore, we exploratively quantified the contributions of the ΔLST to the ΔSOS based on a temperature contribution separation model. We found that there was a negative coupling between SOS and LST in over 90% of the vegetated areas in Hangzhou. At the sample-point scale, SOS was weakly, but significantly, negatively correlated with LST at the daytime (R2 = 0.2 and p < 0.01 in rural; R2 = 0.14 and p < 0.05 in urban) rather than that at nighttime. Besides, the ΔSOS dominated by the ΔLST contributed more than 70% of the total ΔSOS. We hope this study could help to deepen the understanding of responses of urban ecosystem to intensive human activities.

Understanding and Analysing the Urban Heat Island (UHI) Effect in Micro-Scale

2019 ◽  
Vol 10 (2) ◽  
pp. 14-28 ◽  
Author(s):  
Ali Soltani ◽  
Ehsan Sharifi
Keyword(s):  
Heat Stress ◽  
Surface Temperature ◽  
Urban Heat Island ◽  
Metropolitan Area ◽  
Urban Environments ◽  
Heat Island ◽  
Late Afternoon ◽  
Micro Scale ◽  
Daily Cycles ◽  
Urban Heat

The shortage of vegetation cover alongside urban structures and land hardscape in cities causes an artificial temperature increase in urban environments known as the urban heat island (UHI) effect. The artificial heat stress in cities has a particular threat for usability and health-safety of outdoor living in public space. Australia may face a likely 3.8°C increase in surface temperature by 2090. Such an increase in temperature will have a severe impact on regional and local climate systems, natural ecosystems, and human life in cities. This paper aims to determine the patterns of the UHI effect in micro-scale of Adelaide metropolitan area, South Australia. The urban near-surface temperature profile of Adelaide was measured along a linear east-west cross-section of the metropolitan area via mobile traverse method between 26 July 2013 and 15 August 2013. Results indicate that the while the maximum UHI effect occurs at midnight in the central business district (CBD) area in Adelaide, the afternoon urban warmth has more temperature variations (point-to-point variation), especially during the late afternoon when local air temperature is normally in its peak. Thus, critical measurement of heat-health consequences of the UHI effect need to be focused on the afternoon heat stress conditions in UHIs rather than the commonly known night time phenomenon. This mobile traverse urban heat study of Adelaide supports the hypothesis that the UHI effect varies in the built environment during daily cycles and within short distances. Classical UHI measurements are commonly performed during the night – when the urban-rural temperature differences are at their maximum. Thus, they fall short in addressing the issue of excess heat stress on human participants. However, having thermally comfortable urban microclimates is a fundamental characteristic of healthy and vibrant public spaces. Therefore, urban planning professionals and decision makers are required to consider diurnal heat stress alongside nocturnal urban heat islands in planning healthy cities. The results of this article show that the diurnal heat stress varies in the built environment during daily cycles and within short distances. This study confirms that the maximum urban heat stress occurs during late afternoon when both overall temperature and daily urban warmth are at their peak. Literature indicates that diurnal heat stress peaks in hard-landscapes urban settings while it may decrease in urban parklands and near water bodies. Therefore, urban greenery and surface water can assist achieving more liveable and healthy urban environments (generalisation requires further research). A better understanding of daily urban warmth variations in cities assists urban policy making and public life management in the context of climate change.

Evolutionary Consequences of the Urban Heat Island

2020 ◽  
pp. 91-110 ◽  
Author(s):  
Sarah E. Diamond ◽  
Ryan A. Martin
Keyword(s):  
Urban Heat Island ◽  
Urban Areas ◽  
Climatic Conditions ◽  
Urban Heat Islands ◽  
Heat Island ◽  
Heat Islands ◽  
Physiological Tolerance ◽  
Downstream Effects ◽  
Urban Heat ◽  
Evolutionary Consequences

As humans continue to modify the climatic conditions organisms encounter, downstream effects on the phenotypes of organisms are likely to arise. In particular, the worldwide proliferation of human settlements rapidly generates pockets of localized warming across the landscape. These urban heat island effects are frequently intense, especially for moderate to larger sized cities, where urban centres can be several degrees Celsius warmer compared with nearby non-urban areas. Although organisms likely ameliorate the effects of warming through phenotypic plasticity, the evolution of thermally sensitive traits may be an important yet underappreciated means of survival. Recent work suggests the potential for contemporary evolutionary change in association with urban heat islands across a diverse suite of traits from morphology to physiological tolerance, growth rate, and metabolism. This chapter reviews and synthesizes this work. It first develops a comprehensive set of predictions for adaptive evolutionary changes in morphology, physiology, and life-history traits driven by urban heat islands. It then evaluates these predictions with regard to the burgeoning literature on urban evolution of thermally sensitive traits.

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