Testing the Impacts of Sun Exposure and Impervious Surfaces on the Accuracy of Temperature Sensors

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To better understand the impacts of climate change, ecological studies are increasingly addressing the different effects of temperature on organisms and ecosystems. To measure air temperature at biologically relevant scales in the field, ecologists often use small, portable temperature sensors. These sensors must be shielded from solar radiation to provide accurate temperature measurements, bu...

To better understand the impacts of climate change,  ecological studies are increasingly addressing the different effects of temperature on organisms and ecosystems. To measure air temperature at biologically relevant scales in the field, ecologists often use small, portable temperature sensors. These sensors must be shielded from solar radiation to provide accurate temperature measurements, but a review of 18 years of ecological literature indicated that shielding practices vary across studies (when the shielding is reported at all), and that ecologists often invent and construct ad-hoc radiation shields without testing their efficacy.



The project researchers performed two field experiments to examine the accuracy of temperature observations from three commonly used portable data loggers (HOBO Pro, HOBO Pendant, and iButton hygrochron) housed in manufactured Gill shields or ad-hoc, custom-fabricated shields constructed from everyday materials such as plastic cups. They installed replicates of this array of sensors (11 sensor-shield combinations) at 5 different sites at weather stations located in open and forested sites. The team found that HOBO Pro sensors with Gill shields were the most accurate devices. Error in ad-hoc shield treatments ranged from 0.8 to 3.0 °C, with the largest errors at the open site.



They also deployed one replicate of each sensor-shield combination at five sites that varied in the amount of urban impervious surface cover, which presents a further shielding challenge. Results showed that bias in the sensors with ad-hoc shields increased by up to 0.7 °C for every 10% increase in impervious surface.



This study shows that, due to variable shielding practices, the ecological literature likely includes highly biased temperature data that cannot be compared directly across studies. If left unaddressed, these errors will hinder efforts to predict biological responses to climate change. The project team concluded that greater standardization is needed in how temperature data are recorded in the field, handled in analyses, and reported in publications.