Effect of Radiation Shield Type on Air Temperature Measured by Urban Station; Extensive Intercomparison Study in Ostrava, Czech Republic

Abstract Air temperature is the most frequently monitored meteorological variable in urban environments. Although various types of radiation shields are used in city monitoring networks, their impact on measurement accuracy has received limited attention. In this study, we assessed 15 different radiation shields using the same type of temperature sensor over the period 2022–24. Results show that mean daily air temperatures are generally less affected by shield type than daily maximum and minimum temperatures, although statistically significant differences were observed (in most cases, α = 0.001). The tested shields tend to notably overestimate the frequency of very hot days [maximum temperature (TMA) ≥ 35°C], hot days (TMA ≥ 30°C), and summer days (TMA ≥ 25°C), while underestimating the occurrence of warm nights [minimum temperature (TMI) ≥ 17.0°C]; the latter is a crucial index in evaluating human thermal comfort and health impacts. These findings highlight the importance of critically assessing urban meteorological data, especially when used for (urban) climate monitoring and modeling. The results confirm that radiation shields made from UV-stable white plastic provide more accurate measurements at urban stations. Preference should be given to shields that allow easy, regular maintenance. Additionally, medium- to large-scale passive shields with more lamellae and wider spacing are preferred, as they encourage more effective natural ventilation. It is also advisable to incorporate dark-colored, structured undersides into shielding lamellae to eliminate the influence of reflected radiation on temperature sensors. Further research is vital to explore how different urban settings and surfaces may affect the performance of radiation shields.