An innovative method to investigate the altering urban thermal environment by dynamic land cover change: A case study of Suwon, Republic of Korea

The transformation of natural land cover into impermeable materials is a common definition of urbanization. However, it should be noted that vertical growth caused by urban renewal has been disregarded, while the horizontal expansion of urban areas has been widely studied. Understanding dynamic land cover change and its impact focusing on the thermal environment is essential for the sustainable management of urban areas. Therefore, the objective of this study is to propose a simple yet effective urban thermal environment investigation strategy that responds to dynamic land cover transformation. The study area is Suwon, Republic of Korea, where the city has recently been experiencing the most extreme urbanization along with explosive population growth. We designed a three-step approach: 1) extraction of temporal local climate zone (LCZ) to monitor the change in land cover due to urban growth over the period 2004 and 2021, 2) retrieval of high spatial-resolution land surface temperature (LST) using artificial intelligence to observe surface energy flux in heterogeneous urban area in detail, and 3) apply the filtering analysis method, which only uses the pixels classified with a higher confidence level, based on deep learning probabilistic approach to reduce the uncertainty of LCZ classification. To construct the temporal LCZ maps with a 30 m spatial resolution and retrieve the downscaled LSTs (DLSTs) with a corresponding spatial resolution, Landsat series satellites, Shuttle Radar Topography Mission (SRTM), and land cover map produced by Ministry of Environment were used. We obtained the following results: First, the overall accuracy (OA) of the LCZ classification was higher than 90% in both 2004 and 2021. Second, the average coefficient of determination (R²) and root mean square error (RMSE) of the DLSTs were greater than 0.9 and less than 1 °C, respectively. Third, through our suggested urban thermal environment investigation strategy, this study could find that the results of LST changes were clearly varied by building height and compactness changes. Especially, change of low-rise building to mid-rise building increased LST significantly. With these findings, we solidly believe the suggested strategy facilitates advanced urban climate studies.