The Sensitivity of Temperature Measurements to Built-Up Environments: A Case Study In Oak Ridge, TN

It is understood that urbanization or the encroachment of built structures on nearby stations can bias temperature measurements, which can be particularly problematic for stations used in climate monitoring. Documenting the environmental conditions that enhance an urban bias and the reach beyond the built environment can be important to efforts identifying stations that have experienced encroachment. In this study, four instrumented towers were placed at increasingly distant locations (4, 30, 124, and 309 meters) from a small built environment in Oak Ridge, TN. The towers, labeled A (closest to built environment) through D (furthest), were deployed over 1.4 years with tower-B (30 meter tower) relocated 50 meters away from the urban area halfway through the study period. To evaluate the impact of the built environment on temperature measurements, tower observations were compared to tower D, which served as a control. Results showed that unaspirated platinum resistance thermometers (PRTs) were less sensitive to the urban area than aspirated PRTs. In addition, the urban signal had little impact on day time measurements, and was greatest for evenings that followed days with high solar insolation (> 20 MJday^-1). However, the urban signal was not detectable out to tower C (located 124 meters from the urban area). These results suggest that in-situ networks should monitor station surroundings on a regular bases (annually) to detect ongoing and future encroachment, and identifies conditions when the urban signal was enhanced, which could potentially aid in the detection of past encroachment.