Abstract
Agriculture is a $2 billion component of the state economy in Oklahoma. As a result, meteorological, climatological, and agricultural communities should benefit from an improved understanding of soil moisture conditions and how those conditions vary spatially and temporally. The Oklahoma Mesonet is an automated observing network that provides real‐time hydrometeorological observations at 115 stations across Oklahoma. In 1996, sensors were installed at 60 Mesonet sites to provide near‐real‐time observations of soil moisture. This study focuses on 6 years of soil moisture data collected between 1997 and 2002 to analyse the annual cycle and temporal characteristics of soil moisture across Oklahoma. The statewide analysis of the annual cycle of soil moisture revealed four distinct soil moisture phases. In addition, the four statewide phases were also observed in each of the nine climate divisions across Oklahoma, although the temporal characteristics of each phase were unique for each division. Further analysis demonstrated that, at shallow soil depths (5 and 25 cm), the spatial variability of soil moisture across Oklahoma was most homogeneous during the winter and spring periods and most heterogeneous during the summer and autumn periods. Conversely, at greater depths (60 and 75 cm), soil moisture was most heterogeneous during the winter period and the most homogeneous during the late spring. Copyright © 2004 Royal Meteorological Society