Outdoor thermal perception at a beach within a subtropical marine park

Subtropical coastal regions are increasingly important public spaces within urban systems, yet microclimatic conditions and associated thermal outcomes of beaches and coastal areas remain understudied despite growing climate-related heat risks. The field study on Hailing Island, China, combined micrometeorological measurements with thermal perception assessment using thermal indices, including Physiologically Equivalent Temperature (PET), modified PET (mPET), Universal Thermal Climate Index (UTCI), and a human energy budget (EB) approach, to characterize the beach microclimate and evaluate human thermal responses. This study distinguishes between objective thermal stress and individual-reported thermal perception under self-selected exposure. Results showed that the beach surface had high albedo and increased reflected shortwave radiation, thereby intensifying the radiative heat load and contributing to daytime thermal stress. Sea breezes reduced thermal stress under typical sea-land breeze conditions. Tree-covered beach spaces exhibited improved thermal conditions, with denser canopies (e.g., Casuarina equisetifolia L.) providing stronger solar shielding than coconut canopies. Under unshaded beach conditions, air temperature and mean radiant temperature dominated thermal perception, while the influence of air humidity was partly linked to sea-breeze processes. Under tree-shaded conditions, wind speed and mean radiant temperature became the primary drivers. Users demonstrated adaptive behaviors, including preferential use of shaded areas and exposure management in beach zones. Calibrated thermoneutral ranges for beach users were identified as 20.9 to 30.4 °C (PET), 24.7 to 30.7 °C (mPET), 25.8 to 30.8 °C (UTCI), and - 56.1 to 34.8 W m^- 2 (EB). These results provide evidence to support climate-responsive beach design and heat-mitigation strategies in subtropical coastal environments.