Studying the Urban Heat Island Using a Local Climate Zone Scheme

Abstract

IntroductionUrban heat island (UHI), a term first coined in the 1940s, refers to the atmospheric warmth of a city compared to the surrounding countryside. The amplitude of the UHI is usually expressed as the synchronous screen-height air temperature difference between urban and rural thermal sensors [1]. UHI is an unintended outcome of urbanization and this phenomenon occurs in almost all urban areas, which could also lead to increased energy demand and thermal discomfort [2]. Recognized causes of UHI are increases of radiative trapping by complicated urban morphology [3], a decrease in wind speed, energy storage in urban construction, a decrease of evapotranspiration due to the reduction of pervious surfaces in urban areas, and the anthropogenic heat released from social and human activities [4].To investigate the relationships between local climate and urban fabric, researchers have developed classifications such as the flux ratio-active index surface exchange (FRAISE) scheme [5], which defined urban zones that characterize energy partitioning (UZE). Since urban environments can reflect local climate modification to some extent, another approach aims to incorporate urban indicators in designing a climate classification. Urban climatic maps (UCMaps) are based on this approach. UCMaps are built using land use information, topographic information, and climatic data [6].With the same idea, Oke proposed the urban climate zone (UCZ) scheme, a simple urban classification uses descriptors dealing with urban morphology and land use Pol. J. Environ. Stud. Vol. 25, No. 6 (2016), 2609-2616 AbstractWith rapid urbanization and the rise of climate change awareness, policy makers and urban planners are seeking methods and schemes that consider the urban heat island (UHI) effect. In order to investigate to what extent a homogeneous urban fabric leads to a specific thermal pattern, a local climate zone (LCZ) scheme was utilized and classification has been applied in the urban areas of Chongqing. Urban indicators were calculated to match LCZ types of measurement points. Using a mobile measurement approach, we analyzed screen-height air temperature distribution inside local climate zones in both spring and summer. An apparent seasonal difference inside LCZs was found, with air temperature amplitude about 0.8ºC in spring and 0.9ºC in summer. The average air temperature difference in LCZ 1 was 2.9ºC between the two seasons, while in LCZ H this difference was as high as 3.5ºC. The reasons why LCZ H had relatively high air temperature were explained and further investigation of UHI using LCZ scheme was proposed.

Mapping Urban Heat Island Areas in Ibadan

“…The highest LST is observed in high density residential area, commercial/Industrial service and public/educational institutions because its surface property is impervious with low albedo which store and emit more heat. The above result in consensus with the growing body of literature have revealed that LULC is directly associated with increase in (urban) LST and is a significant indicator and factor of UHI formation [37,40,41,42]. Finally, model validation was performed using the Root Mean Square Error (RMSE) method.…”

“…It is evident from Figure 3 that the land surface temperature (LST) varies from one place to another within the metropolitan area, and some areas reflect high temperatures. The rising temperatures of some regions are mainly caused by the thermal property of building materials, dark surfaces with low albedo and urban geometry [36], anthropogenic heat production [37], and finally, the geographic location of the urbanized area [38]. The dip and spike in surface temperatures over water Journal of Management and Service Science (JMSS) A2Z Journals bodies show how water can maintains a fairly constant temperature, due to its high heat capacity [39].…”

Low-Key Stationary and Mobile Tools for Probing the Atmospheric UHI Effect

“…The results from the mobile measurements will be used further to analyze the major urban drivers of UHI intensity in terms of LCZ type [8,52,57,63,[78][79][80][81][82][83][84], and associated impervious area fractions and aspect ratios [29,[85][86][87].…”

Mapping Local Climate Zones: A Bibliometric Meta-Analysis and Systematic Review

“…Modified from Stewart & Oke (2012). Some studies divided meteorological sites into different LCZs based on field surveys (Fenner et al, 2014;Lehnert et al, 2015;Liu et al, 2018;Middel et al, 2014;Müller et al, 2014;Siu & Hart, 2013;Stevan et al, 2013;Stewart et al, 2014;Wang et al, 2016). The LCZ division through field surveys is time-consuming and laborious and can be hardly extended to LCZ mapping on the city scale.…”