Comparative Analysis of Urban Heat Islands in Coastal Cities

Thesis Abstract

Urban heat islands (UHIs) intensify climate exposure and energy demand in coastal cities, where dense urban development interacts with maritime climate, sea breezes, and rising sea levels to shape spatial temperature patterns and thermal comfort. This study addresses the gap in comparative understanding of UHI intensity across coastal metropolitan areas and how local urban form, land use, and mitigation policies modulate these effects. The aim is to quantify and compare UHI characteristics in selected coastal cities, identify drivers, and evaluate mitigation potential. Specific objectives include (1) to quantify UHI intensity and spatial extent in five comparative coastal city contexts using multi-temporal thermal infrared data; (2) to examine the relationship between urban morphology, land cover, and built-environment factors (building density, albedo, green space, water bodies) with surface and air temperatures; (3) to assess the modulating role of coastal dynamics (sea surface temperature, wind regime, and shoreline geometry) on UHI expression; (4) to evaluate the effectiveness of local climate adaptation measures (green roofs, urban forestry, reflective pavements, and zoning) on reducing UHI effects; and (5) to formulate policy-oriented recommendations for climate-resilient coastal urban planning. Methodologically, the study adopts a cross-sectional comparative design based on five major coastal cities with diverse climatic zones and urban morphologies. The population comprises municipal districts within each city; a stratified sampling scheme yields a sample of 50 urban blocks per city, representing residential, commercial, and industrial land uses. Data collection combines remote sensing and in-situ methods Landsat 8/OLI and Sentinel-2 imagery for land surface temperature (LST) retrieval across summer and winter seasons (n=10 scenes per city, total n=50); airborne or UE-based radiometric temperature measurements for validation (n=100 transects); meteorological data from local stations and near-shore buoys; detailed urban form indicators derived from high-resolution GIS layers (building footprints, impervious surface fraction, vegetation indices, albedo estimates). Instruments include calibrated thermal cameras, pyranometers for solar radiation, and standardized surveys of municipal adaptation policies. Validity and reliability are ensured through cross-validation of LST with air temperature at 2 m, inter-scene calibration, and pilot testing of land cover classifications with kappa statistics above 0.80. Analytical approaches encompass descriptive statistics to profile temperature distributions, spatial autocorrelation analyses (Moran’s I) to detect clustering of heat signatures, and regression modelling to quantify drivers of UHI intensity. A two-stage modelling framework is employed (i) generalized additive models (GAMs) to capture nonlinear relationships between temperature and urban form variables, and (ii) hierarchical linear models to account for city-level and district-level variation. The influence of coastal factors is tested via interaction terms between sea breeze metrics (wind speed and direction) and land cover variables. Scenario analysis simulates mitigation effects of greening and reflective surface interventions, using counterfactual LST estimates. Theoretical framing draws on the Urban Climate Theory and the Landscape-Temperature Interaction Model, with integration of the Theory of Planned Behavior to interpret policy uptake. Expected findings indicate that coastal cities exhibit varying UHI intensity spectra strongly associated with building density, impervious surface cover, and green/blue infrastructure presence; sea breeze enhancement in some contexts reduces nocturnal heating but may be attenuated in densely built cores. Green infrastructure and reflective pavements are anticipated to yield measurable reductions in daytime LST by 1.5–3.0°C, with magnitude contingent on baseline urban form and coastal exposure. The study contributes to knowledge by offering a transferable comparative framework linking urban morphology, coastal dynamics, and climate adaptation measures to UHI expression, and by providing context-specific mitigation packages. The study concludes that integrated coastal urban planning—prioritizing permeability of green spaces, increased tree canopy, blue-green corridors, and high-albedo materials—can meaningfully attenuate UHIs in coastal settings, particularly when aligned with wind and shoreline configurations. Policy recommendations include prioritizing district-scale green infrastructure retrofits in high-density cores, adopting reflective paving selectively in sun-exposed zones, and embedding coastal climate resilience in zoning codes. Limitations include potential data gaps in seasonal coverage and spatial heterogeneity within megacities, suggesting future longitudinal monitoring and expansion to additional coastal regions.