Submitted to: Journal of Hydrometeorology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/10/2003
Publication Date: 2/10/2003
Citation: SCHNEIDER, J.M., FISHER, D.K., ELLIOTT, R.L., BROWN, G.O., BAHRMANN, C.P. SPATIOTEMPORAL VARIATIONS IN SOIL WATER: FIRST RESULTS FROM THE ARM SGP CART NETWORK. JOURNAL OF HYDROMETEOROLOGY. 2003. v. 4. p. 106-120. Interpretive Summary: An automated network of soil water and temperature systems was installed at 21 locations in Oklahoma and Kansas in 1996 and 1997 beside pre-existing Department of Energy instrumentation observing the state of the atmosphere. The soil water and temperature systems provide hourly profiles at eight depths, from 0.05 m to 1.75 m below the surface. This network is unique because it provides continuous observations through most of the rooting zone of Southern Great Plains pastures and prairies. A description of the sensor and network, an outline of calibration issues, and example time series from the first three years of operation are presented. Soil water profiles exhibit significant regional, seasonal, and interannual variations. Near-surface soil water varies rapidly between extreme values during the growing season, in response to evapotranspiration and precipitation. Variations in deep (1.75 m) soil water are slower, and mirror climatic precipitation gradients and ecotones, as well as multi-season precipitation deficits. These observations will be useful in energy and water balance research, including linked land-biosphere-atmosphere hydrologic model development and testing.
Technical Abstract: A network of automated soil water and temperature systems was installed at 21 locations in Oklahoma and Kansas in 1996 and 1997, and are providing hourly profiles of soil temperature and water at eight depths, from 0.05 m to 1.75 m below the surface, in the twin profiles 1 meter apart. Dubbed the Soil Water And Temperature System (SWATS), these systems are an addition to the Extended Facilities of the Department of Energy's Atmospheric Radiation Measurement Program's Southern Great Plains Cloud And Radiation Restbed (ARM SGP CART) Site. Average spacing between SWATS systems is about 75 kilometers. The SWATS network is one of three overlapping soil water networks in the region, informally termed MOISTNET, that share a common sensor. The SWATS network is unique among the three, providing observations of available soil water through most of the rooting zone of Southern Great Plains pastures and prairies. A description of the SWATS sensor and network, an outline of calibration issues, and representative time series from the first three years of operation are presented. Of special interest are periods of drying in spring and summer, and subsequent cool season recharge of soil water. Examination reveals systematic seasonal variations in soil water profile characteristics. These spatiotemporal variations are interpreted as the integrated response in varying soils to antecedent soil water and recent precipitation, under varying mixes of vegetation determined by climatic gradients in precipitation, with impacts from local pasture management.