Comparative assessment of high-performance naturally ventilated radiation shields for air temperature measurements

Abstract Accurate air temperature measurements in environmental monitoring networks are essential for various applications. Hence, manufacturers of weather stations have been continuously introducing new improvements to take advantage of technological progress and achieve precise measurements, as much as possible, unaffected by spurious effects. However, while electronic temperature sensors have reached very high levels of accuracy and reliability, radiation shields (RS) remain the most critical component affecting measurement quality. In the last decades, following the increasing diffusion of electronic systems worldwide, the traditional Stevenson screens, as well as their American counterpart, the cotton regional shelter, have been widely replaced either by passive RSs (PRSs), i.e. shields that do not include any active device to prevent overheating, or by forced aspiration RSs, including systems ensuring sensor ventilation. This study presents a field intercomparison of four of the most advanced PRSs commonly used in operational meteorological applications. During 1 year (April 2024–March 2025), identical temperature sensors, protected by different shields, were installed in an experimental field in Friuli Venezia Giulia (Italy). The resulting data were compared using objective statistical analyses based on multiple criteria. Results indicate that the BAR-3, while highly responsive, is prone to overcooling in wet conditions and overheating at low solar elevations. The RAD10 offers good moisture protection and balanced performance, particularly in humid climates, but responds more slowly. The SMART provides reliable behaviour in most conditions, especially in dry or temperate climates, with good responsiveness and limited moisture retention. The COMET shows the best nighttime performance and strong moisture shielding, but is the most susceptible to daytime overheating and has the lowest responsiveness. Our results provide scientific support for identifying possible new reference instruments for operational air temperature measurements, as far as traditional shelters are no longer a global standard.