The Influence of Three-Dimensional Urban Form on the Dynamics of Urban Thermal Patterns: A Case Study of Zagreb, Croatia

This study analyses the influence of three-dimensional (3D) urban form on intra-urban thermal variability and its long-term evolution in Zagreb, Croatia. The research focuses on four residential districts (Špansko sjever, Dugave, Lanište, and Novi Jelkovec) representing different development periods. The central hypothesis is that differences in the development period and urban compactness are associated with differences in summer thermal patterns, with more open spatial configurations generally exhibiting weaker thermal responses than more compact developments. The methodology integrates LiDAR-derived building morphology with a decade-long Landsat time series (2015–2024), including land surface temperature (LST), normalized difference vegetation index (NDVI), and normalized difference built-up index (NDBI). The results indicate a consistent increase in summer LST across all analysed neighbourhoods, with warming rates ranging from approximately 2.00 to 2.83 °C per decade. Built-up intensity shows a positive association with temperature, while vegetation trends are generally weak. A multiple linear regression model explains 47% of the variance in LST (R2 = 0.47), with NDBI identified as a significant predictor (p < 0.01), whereas NDVI and volumetric building density are not statistically significant. Despite this, neighbourhoods with higher volumetric building density (up to ≈2.96 m3/m2) tend to exhibit stronger warming trends compared to lower-density areas (≈1.69 m3/m2), indicating the additional explanatory value of three-dimensional urban morphology. These findings support the concept of a volumetric expression of urban thermal processes, while highlighting that 3D urban morphology contributes to the interpretation of the long-term thermal patterns when considered alongside other factors. They also emphasize the importance of integrating 3D spatial metrics into climate-sensitive urban planning and mitigation strategies.