Submitted to: Journal of Hydrology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/9/2009
Publication Date: 3/30/2009
Citation: Giraldo, M.A., Bosch, D.D., Madden, M., Usery, L., Finn, M. 2009. Ground and surface temperature variability for remote sensing of soil moisture in a heterogeneous landscape. Journal of Hydrology 368(2009) pp. 214-223. Interpretive Summary: Continuous measurements of soil moisture and soil temperature have applications for climatology, agriculture, and natural resource management. However, the point measurements are only useful if they can be related to larger areas. This study examines relationships between point measurements of soil moisture and ground temperature and spatially averaged (in a 30 by 30 m area) measurements. The study examines soil moisture and temperature data collected in the Little River Watershed (LRW) near Tifton Georgia US, utilizing an in situ network of stations operated by the US Department of Agriculture-Agriculture Research Service (USDA-ARS-SEWRL). The results showed good agreement between the in situ station readings and the adjacent 30 by 30 m plot averages. The results confirmed that in this landscape homogeneous 30 by 30 m plots can be used as landscape spatial units for soil moisture and ground temperature studies, with the advantage that small landscape plots can account for local expressions of environmental processes.
Technical Abstract: At the Little River Watershed (LRW) heterogeneous landscape near Tifton Georgia US an in situ network of stations operated by the US Department of Agriculture-Agriculture Research Service (USDA-ARS-SEWRL) was established in 2003 for the long term study of climatic and soil biophysical processes. To develop an accurate interpolation of the in situ readings that can be used to produce distributed representations of soil moisture (SM) and energy balances at the landscape scale for remote sensing studies, we studied 1) the temporal and spatial variations of ground temperature (GT) and infra-red temperature (IRT) within 30 by 30 m plots around selected network stations; 2) the relationship between the readings from the eight 30 by 30 m plots and the point reading of the network stations for the variables SM, GT and IRT; and 3) the spatial and temporal variation of GT and IRT within agriculture landuses (grass, orchard, peanuts, cotton and bare-soil) in the surrounding landscape. The results showed high correlations between the station readings and the adjacent 30 by 30 m plot average value for SM; and site specific, in-field homogeneity in each 30 by 30 m plot. We found statistical differences in the GT and IRT between the different landuses as well as high correlations between GT and IRT regardless of the landuse. High standard deviations were found within the 30 by 30 m plots for IRT, suggesting that when a single point reading for this variable is selected for the validation of either remote sensing data or water- energy models, errors may occur. The results confirmed that in this landscape homogeneous 30 by 30 m plots can be used as landscape spatial units for soil moisture and ground temperature studies, with the advantage that small landscape plots can account for local expressions of environmental processes decreasing the errors and uncertainties in remote sensing estimates normally caused by landscape heterogeneity.