Evaluation of the predictive capabilities of Landsat 7 ETM+ on 50-cm mean annual soil temperature in the Transylvanian Plain, Romania

Mean annual soil temperature has important implications for crops as well as for soil classification and formation. Landsat 7 Enhanced Thematic Mapper Plus (ETM+) band-6 was analysed to determine its relationship with mean annual soil temperature (MAST) at 50 cm in the Transylvanian Plain, Romania. Band-6 is available in both high and low gain formats from the United States Geological Survey; for our study only high gain was evaluated because of the increased resolution that it provides. Both of the gain levels of band-6 are measured at 10.4-12.5 μm (thermal infrared), at 60-m spatial resolution. Four different months of Landsat 7 ETM+ data were used to predict MAST and compared with 50-cm soil temperature data measured on-site with in situ sensors and data logging stations. Despite no correction for land cover differences across the plain, strong relationships were found between the Landsat-predicted and field measured MAST with a coefficient of determination (R ²) for July, August, December and February of 0.63. Multiple regression analysis (MAST _Regression) provided a weaker relationship, when compared with MAST _{in situ}, with a coefficient of determination (R ²) of 0.42. Significant differences existed between urban and agricultural land covers, as identified by Coordination of Information on the Environment (CORINE) data. The use of Landsat 7 ETM+ could reduce the time and expense of large field studies for determining MAST. These data could then be used for temperature models of entire regions, for a range of land management options.