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Comparing Surface and Canopy Urban Heat Islands in Hong Kong with Population Heat Exposure: Integrating Satellite LST and Ground Weather Observations

Yelin Luo
pp.203-208 DOI: 10.62051/tg10nr66 August 13, 2026
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Abstract: Satellite land surface temperature (LST) is widely used to map urban heat, yet it characterizes the radiative state of surfaces rather than the near-surface air that people experience. This study quantitatively compares the surface urban heat island (SUHI) and the canopy-layer (air-temperature) urban heat island (CUHI) over Hong Kong, a high-density coastal subtropical city, and evaluates their implications for population heat exposure. SUHI is derived from Moderate Resolution Imaging Spectroradiometer (MODIS) day/night LST (1 km) and Landsat Collection-2 surface temperature (100 m) for the 2023–2024 warm season, after water masking and an elevation-corrected non-built reference; CUHI is derived from 25 Hong Kong Observatory (HKO) automatic weather stations. Population heat exposure is then modeled with WorldPop 100 m population under two metrics: a surface-temperature proxy and a station-interpolated air-temperature field (leave-one-out mean absolute error 0.3–0.4 °C). Three findings emerge. (1) The surface heat island is much larger in magnitude than the canopy heat island (SUHI spatial range 6–14 °C versus CUHI ~2 °C). (2) Their spatial coupling is weak and scale-dependent: at 1 km no statistically robust station-level association is found (day and night bootstrap confidence intervals include zero), and only a moderate daytime rank association emerges at 100 m (Spearman ρ=0.53, p=0.01). (3) The two exposure metrics diverge: a relative surface proxy ranks 79% of residents in upper-quartile surface heat, whereas the air-temperature metric—tied to local heat-health thresholds—identifies 10% of residents (7% of the elderly) exposed to very-hot-day air temperatures (≥33 °C). Overall, LST usefully maps the surface thermal environment but cannot, without calibration, substitute for canopy-level heat exposure in a high-density coastal city.
Keywords: surface urban heat island; canopy urban heat island; land surface temperature; air temperature; population heat exposure; MODIS; Hong Kong; spatial interpolation; statistical modeling.
APA Citation: Yelin Luo (2026). Comparing Surface and Canopy Urban Heat Islands in Hong Kong with Population Heat Exposure: Integrating Satellite LST and Ground Weather Observations. Transactions on Computer Science and Intelligent Systems Research, 13(1), 203-208. https://doi.org/10.62051/tg10nr66

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