The need for accurate and robust measurements of soil water content has grown as numerical weather models have increasingly incorporated soil moisture variables into simulations of land-atmosphere interactions. To meet this need, measurements of soil moisture have been collected by the Oklahoma Mesonet since 1996. Currently, automated soil moisture sensors are installed at over 100 of the Mesonet sites at depths of 5, 25, and 60 cm. From the output of the sensors, variables such as soil matric potential (MP), fractional water index (FWI), and volumetric water content (WC) are calculated.

During the summer of 2007, soil cores were manually extracted from over 20 Mesonet locations at various intervals. Each sampled location was chosen specifically for its soil texture classification. The soil cores were divided into 5 cm increments from the surface to a depth of 30 cm, and 10 cm increments from 30 to 60 cm. The volumetric water content of these cores was determined and compared to the values reported by the automated sensors at the Mesonet sites. Preliminary analysis has shown that biases exist in the automated sensors when the soil is both extremely wet and dry. A significant percentage of the manually determined WC had a large degree of variability in the range of WC reported at the same location, depth, and time. To augment the 2007 soil core analysis, data from the 2003 Soil Moisture Experiment (SMEX) was also included.