Limited impact of middle shield installation on temperature measurements using TOMST TMS-4 sensors in a grassland experiment

TOMST TMS-4 sensors are widely used in microclimate research, with optional middle shields designed to reduce thermal influences from direct solar radiation and radiation from soil and surrounding surfaces. However, the impact of this shield on temperature readings remains poorly quantified. Here, we report findings from a controlled experiment where sensors with and without the middle shield were deployed under negligible vegetation cover. We examined the effect of the middle shield during both night and daytime hours for one month (05-08-2024 – 04-09-2024) and assessed the effect of windspeed and radiation. We found no substantial temperature differences between shielded and unshielded TOMST TMS-4 sensors in this experiment. We identified an interaction between the shield and solar radiation. This confirms that the shield performs its intended function, mitigating radiation during daylight hours. However, this effect is smaller than other drivers of noise in microclimate data, such as sensor accuracy and environmental heterogeneity, and is unlikely to be ecologically relevant. These findings are important for microclimate researchers, as they suggest that there is little structural bias from middle shield deployment. Further research is needed to assess the impact of middle shield deployment in different environments.