Soil Moisture Dynamics: A Comparison of the SMOS Satellite to the South Fork In-Situ Network

Several publications show a lack of accuracy in weather models that stem from poor representation of soil moisture and evapotranspiration. Currently, soil moisture is commonly gathered through the use of soil probes. These probes frequently have variances in measurements that are tied directly to their locations, even if only a few meters apart. These variances can be caused by soil composition, soil density, placement depth, and the vegetation above the soil. The Soil Moisture and Oceanic Salinity Satellite (SMOS) launched in 2009, is a remote sensing instrument that will help soil moisture and oceanic salinity measurements become more representative of global conditions. The SMOS Satellite uses the emissivity of the soil to gather data on the average soil moisture of the ground from the surface to approximately five centimeters deep. Additionally, the SMOS satellite will remove the differences seen in multiple soil probes by averaging soil moisture across a 40 km footprint, and can frequently collect data from an area several times a week.

This study will compare the soil moisture dynamics seen from the SMOS satellite to an in-situ network of soil probes that represent a single SMOS footprint. Using the United States Department of Agriculture's South Fork data collection site, this study will compare soil drying as observed by the five centimeter depth soil probe network to SMOS observations. Using the statistical analysis of auto-correlation, this study will show how the soil moisture from SMOS and the in-situ networks change during the few days following a rain event with data throughout the months of April through October. My hypothesis is that soil drying in the Midwest is depicted differently by measurements from SMOS compared to the in-situ network because SMOS averages the soil moisture through a five centimeter layer and within its footprint to remove the bias created by soil probes.