Abstract
Urbanization leads to the construction of various urban infrastructures in the city area for residency, transportation, industry, and other purposes, which causes major land use change. Consequently, it substantially affects Land Surface Temperature (LST) by unbalancing the surface energy budget. Higher LST in city areas decreases human thermal comfort for the city dwellers and affects the urban environment and ecosystem. Therefore, a comprehensive investigation is needed to evaluate the impact of land use change on the LST. Remote Sensing (RS) and Geographic Information System (GIS) techniques were used for the detailed investigation. RS data for the years 1993, 2007 and 2020 during summer (March–May) in Dhaka city were used to prepare land cover maps, analyze LST, generate hazard maps and relate the land cover change with LST by using GIS. The results show that the built-up area in Dhaka city increased by 67% from 1993 to 2020 by replacing lowland mainly, followed by vegetation, bare soil and water bodies. LSTs found in the study area were ranged from 23.26 to 39.94 °C, 23.69 to 43.35 °C and 24.44 to 44.58 °C for the years 1993, 2007 and 2020, respectively. The increases of spatially distributed maximum and mean LST were found 4.62 °C and 6.43 °C, respectively, for the study period of 27 years while the change in minimum LST was not substantial. LST increased by around 0.24 °C per year and human thermal discomfort shifted from moderate to strong heat stress for the total study period due to the increase of built-up and bare lands. This study also shows that normalized difference vegetation index (NDVI) and normalized difference water index (NDWI) were negatively correlated with LST while normalized difference built-up Index (NDBI) and normalized difference built-up Index (NDBAI) were positively correlated with LST. The methodology developed in this study can be adapted to other cities around the globe.
Highlights
Urban land use changes play an important role in influencing regional climate (Jahan et al 2021; Nagarajan and Basil 2014; Grimm et al 2008)
The specific objectives of this study are: to investigate LULC changes from 1993 to 2020 in Dhaka City; to analyze the impact of LULC changes on Land Surface Temperature (LST) during summer as the warming effect is more hazardous during summer in the city; to explore the human thermal comfort (HTC) of Dhaka city at surface level; to examine the relationship between LST and LULC indices such as Normalized Difference Vegetation Index (NDVI), Normalized Difference Water Index (NDWI), Normalized Difference Bareness Index (NDBAI) and Normalized Difference Built-up Index (NDBI)
The derived land cover maps were validated against the remote sensing images captured by Google Earth and Sentinel-2 in different random locations in the study area (Fig. 2) for the year 2020 as the high resolution remote sensing images for Sentinel-2 were available for this year
Summary
Urban land use changes play an important role in influencing regional climate (Jahan et al 2021; Nagarajan and Basil 2014; Grimm et al 2008). Converting natural vegetated surfaces into impermeable builtup surfaces is responsible for changing regional climate (Argueso et al 2013; Imran et al 2018, 2019a). This impermeable built-up surface called urbanization refers replacing of natural surfaces with different man-made structures such as industrial and residential buildings, roads, parking lots, impervious surfaces (Babalola and Akinsanola 2016; Pu et al 2006; Patra et al 2018). The excess heat stored in built-up surfaces and lacks humidity in the air substantially increases LST when vegetated surfaces are converted into built-up surfaces
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