Causes Of Urban Heat Island Research Articles

Development of Pavement-Surface Temperature Predictive Models: Parametric Approach

AbstractRapid urbanization has been causing a change in the urban climate resulting in urban heat islands (UHIs). In the area of transportation pavement infrastructure and its effect on UHI, the impact of these changes can be reduced by using road materials that are low-temperature sensitive. Previous studies indicated that an increase in the impervious nature of urban grounds is one of the main causes of UHI, which is principally affected by pavement surface temperatures. Further, the associated predictive models focused on pavement temperature profiles along the depth of the system, discounting surface parameters such as solar flux and surrounding air temperature. This study established pavement-surface temperature models based on meteorological factors, which can be used to estimate heat energy flux from different pavement materials and systems. The models encompassed more than 670 data points, which were robust and represented low bias and very high precision (depicted by Radj2≥98% and Se/Sy≤0.13), an...

A Study of the Effect of Building Designs on Climate Change: Mitigation and Adaption

Urbanization and development are the inevitable consequences of economic growth. With urbanization, various issues of climate change are cropping up. Urban Heat Island (UHI) is a significant phenomenon to manifest the changes in climate of a region. The present research attempts to establish the presence of this phenomenon in Roorkee, India on one hand. And, to study change in architectural styles of the buildings in the course of time as the possible reasons of these climatic differences on the other hand. Finally, the research concludes with recommendations and suggestion to mitigate and adapt to climate changes through the implementation of an indigenously designed algorithm. Index Terms—Uhi, surface transformation, land surface temperature, minimum u-value algorithm. I. I NTRODUCTION Urbanization has lead to transformation of natural surfaces to urban land. Construction of buildings and infrastructure has made undue unavoidable changes in land surface properties. One important property is the land surface temperature (LST). LST is responsible for the change in air temperature of a region (1). Anthropogenic activities like use of vehicles and air conditioners, and emission of gases is also responsible for the same. But urban development plays a major role. The type of building material used and the percentage of natural land transformed to urban land are solely responsible for the change in land surface properties. This further result in change of local weather conditions and eventually leads to climate change. The construction of buildings, roads and other impervious surfaces leads to increase of temperature of that region as compared to the surrounding rural area. This phenomenon is known as Urban Heat Island (UHI) (2). UHI is a significant manifestation of climate change. The present study aims to investigate the presence of UHI in Roorkee, India. 268 meters from mean sea level, Roorkee has an extreme and erratic continental climate. The paper also studies the architectural and construction styles of the various buildings in the study area to empathize the causes of UHI.

The Effects of Road and Other Pavement Materials on Urban Heat Island (A Case Study of Port Harcourt City)

Urban centers are consistently exhibiting higher temperature than its surrounding suburban rural areas. The large amount of heat generated from urban structures such as road materials and pavement materials and other anthropogenic heat sources are the main causes of Urban Heat Island (UHI). The sources of data for this research included primary and secondary sources. Other techniques employed for data collection were direct measurement and readings on the road and pavement materials. The research found out that, there was consistency in rising temperature at different time of the day by the different road and pavement materials. Asphalt has the greatest effect of increasing the urban temperature four degrees higher, followed by concrete, three degree rise in temperature, and earth (ordinary ground) by two degree rise and vegetation (grass) by one degree rise in temperature. The overall effect on the residents of the study area ranges from increase in hotness of the day; 44.6% respondents agrees; while 34.3% says it affects the ambient air quality of the area, and other effects such as increased ground level ozone, suffocation, sleeplessness and restlessness as a result of excessive high temperature especially at night are identified in this paper. The research recommends the review or redesigning of the entire Port Harcourt city Master Plan to make provision for creation of more green areas rather than pavements and concreted areas to reduce the effects of (UHI) and ultimately improve the comfort and living conditions of the people in a the garden city Port Harcourt.

Study of the Level of Awareness of the Iraqi Society to the Impact of Climate Changes

Baghdad is a large city, warmer than surrounding areas due to the urban heat island effect. This research is to understand what Iraqi society segments thought about issues represented a tangible threat to their urban environment and lifestyle. Questions were establish what scholars, student and Architect thought about the impact of climate change and UHI. Analysis indicated that there was a moderated acceptance in society segments, students, scholars and low among the urban residents of Iraqi society that complex issue such as Urban Heat Island as part of climate change was occurring and an even lower acceptance that it was the result of human activity. Nonetheless, the low acceptance reflected a high degree of uncertainty among urban people rather than widespread open skepticism. The uncertainty among urban residents could be attributable to scientific discrepancies about causes of Urban Heat Island and the possible consequences. The results show that trust in science and scientific credibility has been undermined by these discrepancies and the perception that scientists are using climate change to pursue their own agendas. With only 52% of educated survey respondents believing that climate change and Urban Heat Island information were easy to understand, there was a clear need to reconsider communication strategies for the dissemination of scientific information in universities and institutes. Results indicate that minimal adaptive responses of Iraqi society to changes in local climate, current and past extreme changes in Iraqi urban temperature, water scarcity and dust storm seasons support results that indicate society did not prioritize Urban Heat Island imperative. Generally, well-educated community did not recognize or underestimated the short to medium term risk Urban Heat Island represented for their urban environment or lifestyles.

Change of Wind Velocity Caused by the Development of Downtown Areas: A Case Study in Jeonju Korea

The development of downtown areas causes urban heat island (UHI), which raises the temperature of cities. To remove the causes of UHI, extensive research is underway for securing green spaces and fresh air corridors in urban districts. The development of high-rise apartments in the downtown affected the fresh air corridor of the whole city, decreasing wind velocity by up to 50% compared to that before the development. In addition, with regard to apartment layout in complexes, the front-rear inter-building distance had a higher effect on the change of wind velocity in the complexes than the side-to-side inter-building distance. However, in a layout with the same repetitive form, a wide side-to-side space increased the intensity of turbulent flow in the complex, making the wind velocity almost three times higher at some parts.

URBAN HEAT ISLAND AND CITIES DESIGN: A Conceptual Framework of Mitigation Tools in Hot‐arid Regions

Urban heat island (UHI) is a climatological phenomenon which represents the difference inair temperature between urban areas, and its surrounding suburbs and undeveloped areas.UHI is considered as one of the major problems in the 21st century posed to human beings asa result of high rates of urbanization. The large amount of heat generated from urbanstructures, as they absorb and re‐radiate solar radiation, and from anthropogenic heatsources are main causes of UHI. In the ever‐urbanizing Arab region, the intensifying UHIcontributes to the increase of thermal discomfort of urban dwellers and, hence, the increaseof their environmentally unsustainable practices. There is an utmost need, therefore, tostudy this phenomenon and investigate possible mitigation tools.This paper summarizes the significance of UHI, its major characteristics and its causes. Moreimportantly, it attempts to form a conceptual framework of countermeasures, and urbandesign and planning parameters which help mitigate this phenomenon. In doing so, thistheoretical study capitalizes on immense literature which has addressed the issue, yet,basically from a climatological point of view. It attempts to look at the subject from an urbandesign and planning point of view. The study, therefore, brings together two disciplines,climatology and cities design and planning, an attempt in the field of UHI that has beenrarely tackled on the Arab region. The resulting collective conceptual framework is seen inthis paper as a necessary first step towards deeper investigation into urban planning anddesign parameters which could help reduce the impact of UHI and, hence, create betterquality of life in the Arab world.

Approaches to study Urban Heat Island – Abilities and limitations

Urban Heat Island (UHI) has significant impacts on the buildings energy consumption and outdoor air quality (OAQ). Various approaches, including observation and simulation techniques, have been proposed to understand the causes of UHI formation and to find the corresponding mitigation strategies. However, the causes of UHI are not the same in different climates or city features. Thus, general conclusion cannot be made based on limited monitoring data. With recent progress in computational tools, simulation methods have been used to study UHI. These approaches, however, are also not able to cover all the phenomena that simultaneously contribute to the formation of UHI. The shortcomings are mostly attributed to the weakness of the theories and computational cost. This paper presents a review of the techniques used to study UHI. The abilities and limitations of each approach for the investigation of UHI mitigation and prediction are discussed. Treatment of important parameters including latent, sensible, storage, and anthropogenic heat in addition to treatment of radiation, effect of trees and pond, and boundary condition to simulate UHI is also presented. Finally, this paper discusses the application of integration approach as a future opportunity.

Urban heat island diagnosis using ASTER satellite images and ‘in situ’ air temperature

This study demonstrates that thermal satellite images combined with ‘in situ’ ground data can be used to examine models of heat island genesis and thus identify the main causes of urban heat islands (UHIs). The models, although proposed over 30 years ago, have not been thoroughly evaluated due to a combination of inadequate ground data and the low resolution of thermal satellite data. Also there has been limited understanding of the relevance of satellite-derived surface temperatures to local and regional scale air temperatures. A cloud-free ASTER thermal image of urban and rural areas of Hong Kong was obtained on a winter night with a well-developed heat island, accompanied by a 148 km vehicle traverse of air temperatures. Over the whole traverse a high R 2 of 0.80 was observed between surface and air temperatures, with the two datasets showing a similar amplitude and general trend, but with the surface exhibiting much higher local variability than air temperature. Gradients in both surface and air temperature could be related to differences in land cover, with little evidence of large scale advection, thus supporting the population/physical structure model of UHI causation, rather than the advection model. However, the much higher surface and air temperatures observed over the largest urban area, Kowloon, than over any smaller urban centre with similar physical structure in the New Territories, would seem more indicative of the advection model. The image and ground data suggest that Kowloon's urban canopy layer climate is mainly influenced by local city structure, but it is also modified by a strongly developed, regional scale urban boundary layer which has developed over the largest urban centre of Kowloon, and reinforces heating from both above and below.

A review on the generation, determination and mitigation of Urban Heat Island

Urban Heat Island (UHI) is considered as one of the major problems in the 21st century posed to human beings as a result of urbanization and industrialization of human civilization. The large amount of heat generated from urban structures, as they consume and re-radiate solar radiations, and from the anthropogenic heat sources are the main causes of UHI. The two heat sources increase the temperatures of an urban area as compared to its surroundings, which is known as Urban Heat Island Intensity (UHII). The problem is even worse in cities or metropolises with large population and extensive economic activities. The estimated three billion people living in the urban areas in the world are directly exposed to the problem, which will be increased significantly in the near future. Due to the severity of the problem, vast research effort has been dedicated and a wide range of literature is available for the subject. The literature available in this area includes the latest research approaches, concepts, methodologies, latest investigation tools and mitigation measures. This study was carried out to review and summarize this research area through an investigation of the most important feature of UHI. It was concluded that the heat re-radiated by the urban structures plays the most important role which should be investigated in details to study urban heating especially the UHI. It was also concluded that the future research should be focused on design and planning parameters for reducing the effects of urban heat island and ultimately living in a better environment.

Simulation of surface urban heat islands under ?ideal? conditions at night part 2: Diagnosis of causation

A simple energy balance model which simulates the thermal regime of urban and rural surfaces under calm, cloudless conditions at night is used to assess the relative importance of the commonly stated causes of urban heat islands. Results show that the effects of street canyon geometry on radiation and of thermal properties on heat storage release, are the primary and almost equal causes on most occasions. In very cold conditions, space heating of buildings can become a dominant cause but this depends on wall insulation. The effects of the urban ‘greenhouse’ and surface emissivity are relatively minor. The model confirms the importance of local control especially the relation between street geometry and the heat island and highlights the importance of rural thermal properties and their ability to produce seasonal variation in the heat island. A possible explanation for the small heat

THERMAL BEHAVIOR OF URBAN LANDSCAPES AND THE URBAN HEAT ISLAND

The cause or causes of urban heat islands have puzzled scientists for more than a century. Investigators have observed a close relation between urban land cover and urban temperature patterns. A proposed explanation of this relation is that the thermal inertia of urban surfaces is larger than rural interface thermal inertia. However, recent METROMEX and remote sensor satellite observations do not appear to support this view. The thermal inertia model of the urban interface ignores urban canopy structure and composition. Specifically the hollow structure of buildings reduces the thermal mass and thus the apparent thermal inertia of these structures compared with pavements. Numerical modeling results of the thermal behavior of a two-layer interface and aircraft far-infrared remote sensor observations of urban landscapes demonstrate the differential thermal behavior of buildings versus pavements. Accounting for the structure and configuration of urban canopies explains observed urban landscape thermal behavior and should assist in explaining the urban heat island phenomenon.