RAIN CHECK: VARIATIONS IN THE GEOSTATISTICAL STRUCTURE OF GROUND TEMPERATURE SURVEYS, YELLOWSTONE NATIONAL PARK, USA

This study considers the differences in spatial correlation structures of shallow ground temperatures in an active hydrothermal area. Here we analyze and compare two separate ground temperature measurement surveys conducted on the same grid on separate days. Both surveys were conducted in approximately three hours and are identical save for ambient conditions preceding and during their collection times. Conditions for the first survey were sunny and dry during and preceding the data collection, while the other had significant precipitation the day before and light precipitation during the data collection. The thermal area is a wide meadow that drains the nearby low-relief hills and numerous hot springs. After precipitation events there are several locations of minor standing water within the grid. This higher degree of saturation and the evaporative cooling due to precipitation in the atmosphere presumably influences the spatial distribution of temperatures across the grid. We explore the cutoff values in the continuous indicator semivariograms of the surveys to distinguish the thermal regimes of a given generating process - e.g., diffusion through the soil, advection along fractures acting as fluid pathways, or lateral groundwater flow. Differences between the ‘dry’ and ‘wet’ survey experimental semivariograms will aid in refining methods for conducting shallow ground temperature measurement surveys.