Seasonal Interaction Effects of Microclimate and Built Environment on Elderly Outdoor Activities: A Case Study in Xi’an, China

Microclimate and built environment jointly influence outdoor activities among the elderly. However, existing studies largely focus on a single season or environmental factor, lacking a comprehensive analysis of seasonal variation and multi-factor coupling effects. This paper investigates the seasonal interaction effects of microclimate and built environment on elderly outdoor activities, with implications for elderly-friendly urban design. Using a typical residential neighbourhood in Xi’an as a case, we constructed a multi-source spatio-temporal dataset through high-density microclimate monitoring in winter and summer, fine-grained POI mapping, and computer-vision-based behavioural annotation. Generalised Additive Models (GAM) and SHAP analysis were employed for modelling and mechanism exploration. The results show that: (1) Elderly activity patterns exhibit a fundamental seasonal reversal—characterised as “sun-seeking and wind-avoiding” in winter and “shade-seeking and wind-pursuing” in summer; (2) Environmental factors exhibit marked nonlinear and threshold-dependent influences that vary by season; (3) Microclimate and built environment elements demonstrate synergistic interaction effects, especially pronounced in summer. Quantitatively, GAM and SHAP analyses indicate that the “effective service radius” of Elderly-Friendly POIs (defined as the threshold where positive influence approaches zero) contracted from approximately 45–50 m in winter to 35–40 m in summer, while their peak promotional effect occurred at 20–25 m. Positive POIs exhibited a significantly shorter influence range, and Negative POIs demonstrated negligible distance-dependent effects. This study confirms a “seasonal dynamic interaction” mechanism and proposes the adaptive design strategy of “sunlight and wind-shelter pockets—shade and ventilation corridors,” offering empirical and methodological support for climate-responsive elderly-friendly community planning.