Thermal Environment Response Mechanism of Old Urban Blocks in Coastal County Towns of Southeast Zhejiang Based on a Multi-Season Empirical Analysis

This study focuses on a typical old urban block in Rui'an City, Zhejiang Province, exploring the quantitative relationship between urban external morphology and human thermal comfort. The aim is to establish an evaluation index system for urban regeneration that is applicable to old urban blocks in coastal county towns. The study conducted a year-long meteorological observation and microclimate simulations to create a long-term dynamic monitoring sequence for the summer, transition, and winter seasons. It extracted 20 spatial morphology indicators and established an XGBoost-SHAP nonlinear regression model combined with the UTCI. The results indicate that: 1) air temperature, humidity, and wind speed exhibit significant variations across the three seasons due to differences in spatial morphology; 2) sky view factor (SVF), frontal area index (FAI), paved area ratio (PAR), and near-line ratio (NL) are key factors influencing courtyard thermal comfort; 3) the effects of different spatial morphology quantification indicators on thermal comfort vary significantly across different seasons. In winter, the optimal morphological ranges for thermal comfort are: SVF at 0.55–0.75, NL at 0.03–0.10, FAI at 0.3–1.0, and PAR at 0.1–0.3, which strike a balance between shading, ventilation, thermal insulation, and the surface thermal environment. The study enriches theoretical research on the quantitative relationship between microclimates and spatial morphology, providing targeted optimization strategies in practice and offering data support and references for low-carbon urban regeneration and sustainable community development in coastal county towns of southeast Zhejiang.