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.