DETERMINING TERRAIN EFFECTS ON SUBSURFACE TEMPERATURE USING REMOTE SENSING

We used remote sensing to make determinations of terrain effects on boreholes of the United States in the IHFC paleoclimate data set. We define terrain effect as topography, land usage change, and direct and diffused sun radiation, as well as slope angle, and natural elements such as groundwater and snow. We have obtained images of the boreholes from a variety of sources including aerial photography and satellite imagery using several search engines such as Google Earth, TerraServer, Geocommunities and Topozone. We initially singled out questionable boreholes by examining their temperature depth profiles. We obtained borehole T-z profiles from the IHFC website (http://www.geo.lsa.umich.edu/IHFC/). SAT data were obtained from USHCN climate zones near the IHFC boreholes. Background heat flow was removed from the IHFC data to create reduced T-z profiles and synthetic T-z profiles were derived using the SAT data as forcing signals in 2-D finite difference conductive heat flow models. The reduced T-z profiles were smoothed to remove noise due to variations in thermal conductivity for better visual effect. Borehole percentages of possibly problematic boreholes are given as follows; total boreholes examined in the United States = 130, boreholes with terrain effects = 33/130 = 25.4%. The breakdown is: City/Urban effects = 6/130 = 4.6% Proximity to large bodies of water = 5/130 = 3.5% Hill Effects-Ravines, Valleys, Buttes = 16/130 = 12.3% Mining Operations = 3/130 = 2.3% and Mixed Effects = 3/130 = 2.3%. We selected a few boreholes for a focused investigation because their T-z profiles deviated significantly from the SAT derived synthetic profiles. In these cases, terrain effects did play a significant role in subsurface temperature deviations from surface air temperature. Ultimately, we wish to physically log as many boreholes as possible and gather field data on terrain effects and land usage over time.