The Influences of Thermal Diffusivity and Weather on Shallow (2-Meter) Temperature Measurements

Abstract

Multiple measurements of shallow temperatures over time and at multiple depths have been used in combination with surface weather data to better characterize and quantify the effects of thermal diffusivity and weather variations on 2-meter temperature surveys. Shallow soil and rock thermal diffusivities were calculated by measuring the attenuation of the annual temperature wave between depths of 1.5 and 2 meters. The results indicate that thermal diffusivity-induced temperature variations are relatively minor at Desert Peak, typically on the order to 0-1°C at a depth of 2 meters, compared to the strength of the geothermal heat flux signature. The results also confirm that thermal diffusivity effects are minimized in surveys run shortly after the autumn and spring equinoxes, compared with other times of year. The influences of weather patterns are easily seen at a depth of 1 meter but are more negligible at 2 meters, which provides an incentive to conduct surveys at the greater 2-meter depth, as opposed to 1 meter.