How Do the Dynamics of Urbanization Affect the Thermal Environment? A Case from an Urban Agglomeration in Lower Gangetic Plain (India)

Urbanization is one of the significant anthropogenic impacts on the earth in terms of land use and land cover (LULC) [1,2]. Thus, urbanization has a crucial impact on the thermal environment and the emergence of the urban heat island (UHI) effect [3,4]. Urbanization transforms the natural land cover into artificial surfaces [5]. The impacts of anthropogenic activities are more prominent due to unplanned urbanization [6,7]. Thus, the LULC dynamics largely affect urban and sub-urban landscapes, leading to the increase in temperature and the emergence of the UHI effect [8,9]. The temperature in the urban areas is higher than the surrounding environment [10,11]. The emergence of the UHI effect significantly affects people’s quality of life and results in eco-environmental degradation [12]. Besides ecological consequences, the UHI effect also causes deterioration of air quality, human health, and thermal comfort level [13,14]. Therefore, the assessment and monitoring of UHI has become one of the significant research issues in urban climatology, urban landscape, and urban geography [15,16]. The changes in surface properties are the prime factors affecting the UHI effect [15]. Therefore, it is crucial to explore the relationship between landscape patterns, composition, configuration, and the urban thermal environment (UTE) [2,17,18]. These studies showed that landscape patterns had a tremendous impact on LST. Maimaitiyiming et al. [19] conducted a survey in Asku city in China and showed the impact of green space (GS) on the land surface temperature (LST). According to Asgarian et al. [20], the connectivity and complexity of the urban landscapes increased LST due to the high energy between landscapes. The loss of GS and blue space (BS)increased LST, whereas the expansion of GS generates a cooling effect in urban areas [21]. However, most studies were conducted on the relationship between LST and land cover types [22,23]. The impact of landscape configuration and composition on the LST from the perspective of UHI is essential for climate-sensitive planning strategies in cities [5].

Globally, accelerated urbanization, continued population growth, and loss of green infrastructures (GI) increased temperatures, significantly affecting human health and thermal comfort level [7,24]. At the Climate Conference (2018) in Paris, it was stated that the temperature across the globe increased substantially, and several recommendations were suggested, such as reducing carbon emissions and green house gas (GHG) and use of renewable energy [24]. Thus, studying and understanding the UHI phenomenon is crucial to reducing the influence of climate change and finding possible measures and strategies [7]. UHI effect can be accessed from two perspectives, namely UHI related to the surface (SUHI) and UHI related to the atmosphere (AUHI) [25]. SUHI is assessed based on the LST, and AUHI is assessed based on the air temperature [7]. This study analyzed UHI based on the LST retrieved from remote sensing (RS). The rapid urban expansion and population growth in the cities of developing countries have strengthened the UHI effect [26]. In India, very limited studies were carried out on the relationship of landscape composition with LST from the perspectives of UHI phenomena. English Bazar Urban Agglomeration (EBUA) has extended because of the growth of the population and rapid urban expansion [27]. Recent studies showed that EBUA had experienced a dramatic transformation of LULC and a significant increase in built-up areas [27,28]. For example, according to Dutta and Das [29], the EBUA built area increased from 6.99% (14.75 KM²) to 7.22% (15.80 KM²). Dutta and Das [29] conducted another study in EBUA on the spatiotemporal pattern of regional heat islands (RHI) and found that mean LST increased by 1.73 °C from 1990 to 2015. A study performed by Ziaul and Pal [30] to examine the outdoor thermal comfort (OTC) level in EBUA found that the area under highly uncomfortable areas increased from 3281.4 ha (2010) to 4815 ha (2016). Thus, from the previous research studies, a few notable research gaps can be highlighted. Firstly, previous studies mostly focused on the identification of urban growth patterns, landscape fragmentation due to urban expansion, the pattern of UHI, and the relationship between LULC and LST. However, the impact of urbanization on the thermal environment with a validated framework has remained unexplored. This is the first attempt to explore the impact of urbanization on the thermal environment with a validated framework. This study aims to explore the influence of landscape pattern, composition, and configuration on the thermal environment using geospatial and gradient approaches. The fundamental objective of this study is to explore the impact of landscape pattern, composition, and configuration on thermal environment along URG.