Simulation and Evaluation of Hourly Outdoor Thermal Environment on an Annual Basis

The outdoor thermal environment varies significantly across time and space due to changing weather conditions and complex urban geometries. A comprehensive, high-resolution annual analysis is essential to capture these dynamics and support informed urban design decisions. This study presents a framework for calculating and evaluating urban thermal conditions on an annual basis while maintaining an affordable computational burden. The framework utilizes satellite imagery to recognize city geometry, identifying buildings, trees, and water bodies. Meteorological data drives the rapid simulation of key parameters in outdoor thermal environment: Wind speed and Mean Radiant Temperature (MRT). The system combines Fast Fluid Dynamics (FFD) and Proper Orthogonal Decomposition (POD) for efficient wind simulations, alongside GPU-parallel ray-tracing algorithms for MRT calculations, ensuring accurate and efficient evaluations of complex urban environments. After annual hourly flow and radiation fields are obtained, outdoor thermal stress is quantified through the Universal Thermal Climate Index (UTCI), with the assumption of uniform air temperature and humidity distribution. The framework was validated with measured data from Shanghai Jiao Tong University (SJTU) campus, achieving robust predictive performance with an R² value of 0.95 for UTCI estimations. The framework spent a computational time of 5.67 hours on a 64 core workstation to predict annual thermal environment of the entire SJTU campus (2.3km×1.3km) . The results provide key insights for urban planners, including Outdoor Thermal Comfort Autonomy (OTCA) maps for identifying areas that require improvement and hourly thermal stress evaluations to pinpoint critical discomfort periods. These outputs inform strategic decisions on functional zoning, urban renewal, and seasonal adaptive design, ultimately enhancing urban comfort and health.