Abstract
Urban Heat Island intensification is among the most visible environmental consequences of rapid urbanization, emerging as vegetated land is converted into impervious surfaces such as asphalt, concrete, and rooftops. In Surabaya, Indonesia's second-largest metropolitan city, sustained urban expansion over the past two decades has heightened concerns about growing thermal vulnerability, yet existing Surface Urban Heat Island (SUHI) studies in the city have relied on vegetation-oriented indices (NDVI, NDBI) and single-date imagery, limiting their ability to isolate impervious surfaces specifically or capture how this relationship evolves over time. To fill these research gaps, this study implements the Normalized Difference Impervious Surface Index (NDISI) utilizing a multitemporal framework from 2020–2025 based on Landsat 8/9 imagery. Using simple linear regression, NDISI, LST and SUHI extent were extracted and analyzed with R (the Pearson correlation coefficient), determination coefficient (R²) values and significance tests (α = 0.05). Results indicate an increase in impervious surfaces over the study period, especially in city centre, residential and industrial areas that was accompanied by increased extent and intensity of SUHI. For the “annual” regressions, R values ranged from 0.40–0.52 (R² = 16.06–27.16%), while for the pooled dataset (2020– 2022) R = 0.445 and R² = 0.1985 (p < 0.05). This study generated the first real multitemporal SUHI baseline for Surabaya based on NDISI data, which connects directly to methodologies applied in geospatial-based planning initiatives such as green open space planning and sustainable urban management within rapidly growing tropical coastal cities compared with temporal assessments provided by single-date (vegetation-index)-based studies.