Assessment of Surface Urban Heat Island in Indonesia's Municipal Cities

Surface Urban Heat Island (SUHI) is a well-known phenomenon where the land surface temperature of urban regions is warmer than surrounding rural areas. The quantification of its intensity over cities is important to understand its influence on the local climate and for mitigation measures and planning. This study aims to assess the intensity of SUHI by measuring the Surface Urban Heat Island Index (SUHII) and Urban Thermal Field Variance Index (UTFVI) over 513 municipal cities–districts in Indonesia by utilizing satellite-derived Land Surface Temperature/LST and Enhanced Vegetation Index/EVI products within 2001–2022 period. The SUHII and UTFVI were calculated by comparing the LST area based on the administrative polygons for each city and surrounding neighborhood districts. The trends of UHI's extension were analyzed by performing the Mann–Kendall test and Sen’s slope to the time series of the SUHI area (pixel counts) defined by UTFVI values. The result shows that the top 10% of cities–districts in Indonesia's provinces, are categorized as cities (ranked by LST) and are mainly located in Java Island, Indonesia's most populated region. Among them, 23 cities experienced a significant increasing trend of SUHII and significant spatial extent to the neighboring districts for daytime SUHI and 8 cities for nighttime SUHI. In addition, the current finding also reveals that the extension of the SUHI area for some cities has crossed the municipal or administrative boundary of the city, alarming to urban heat extension that might be contributing to regional or global warming.