Decoupling the Nonlinear Effects of Urban Morphology on Thermal Resistance, Recovery, and Adaptation under Press–Pulse Disturbances

The escalating frequency of extreme heatwaves and rapid urbanization pose unprecedented challenges to urban thermal environments. While current UHI research has established robust static mitigation strategies, it remains limited in capturing the dynamic pathways of urban systems during and after acute thermal shocks. Specifically, the post-disturbance recovery and non-linear thresholds that govern systemic resilience under extreme heat remain largely under-explored.  To bridge this gap, we establish a resilience-oriented framework grounded in Press–Pulse Disturbance (PPD) theory, which we operationalize via a Pulse Intensity Index (PII) to quantify acute Pulse disturbances. Within this framework, we evaluate the system’s dynamic response through three dimensions: Resistance (the max temperature deviation from the thermal baseline during the peak Pulse period), Recovery (the restoration rate of LST toward the baseline post-disturbance), and Adaptation(the thermal baseline represents a long-term structural adjustment aimed at addressing long-term urbanization pressure).
The research focuses on the Seoul Metropolitan Area (SMA) during 26years (2000–2025). (1) We utilized Google Earth Engine to retrieve Land Surface Temperature from multi-temporal Landsat imagery, fused multi-source remote sensing and meteorological data. (2) The PII integrates heatwave frequency (>= 33°C, KMA standards) with cumulative excess perceived heat, providing a robust physical baseline for evaluating systemic responses to acute shocks. (3) We constructed a multi-dimensional indicator system across these categories: Built-up structures, GI and road composition. These indicators were processed through unsupervised clustering to urban morphological typologies. (4) An explainable machine learning model (LightGBM) integrated with SHAP values was employed to decouple the nonlinear and marginal effects of these morphological categories on resilience metrics.
Findings reveal significant spatial heterogeneity in thermal resilience across SMA. 1) During 2025 heatwave, areas under intense thermal load demonstrated a notable resilience decay as green infrastructure reached its critical threshold in cooling efficiency, especially PII was 41.9 in Seoul compared to only 2.3 in 2010. 2) High-density urban cores exhibited a difference in Resilience and Recovery. Although the shading effect enhanced immediate resilience, canyon heat retention led to a sharp decline in resilience compared to medium-density areas. 3) LightGBM model identified a critical threshold for GAC; below this morphological limit, adaptation capacity diminishes abruptly regardless of built-up and GI configurations.
This study underscores that urban thermal resilience is a dynamic response shaped by the synergy between chronic urbanization pressures and acute climatic shocks. The identified nonlinear relationships and threshold effects indicate that undifferentiated urban greening strategies are insufficient for mitigating extreme heat risks across diverse urban fabrics. Our findings establish a methodological workflow—linking urban expansion to resilience identification—thereby providing spatially targeted optimization strategies. This research provides a scientific basis for urban planners to shift from general mitigation to targeted structural interventions, ensuring enhanced climate-adaptive capacity for future extreme scenarios.

This work was supported by Korea Environment Industry &Technology Institute (KEITI) through "Climate Change R&D Project for New Climate Regime.", funded by Korea Ministry of Environment (MOE) (RS-2022-KE002123).