TITLE: CEOP CPPA ARM SGP Soil Temperature and Soil Moisture Data Set CONTACT: Raymond McCord Building 1507 PO Box 2008, MS 6407 Oak Ridge, TN 37831-6407 Telephone: (865) 574-7827 Fax: (865) 574-4665 E-Mail: firstname.lastname@example.org 1.0 DATA SET OVERVIEW This data set contains 60-minute resolution soil temperature and soil moisture data from the Coordinated Energy and Water Cycle Observation Project (CEOP) Climate Prediction Project for the Americas (CPPA) Reference Site operated by the Atmospheric Radiation Measurement (ARM) Program at its Southern Great Plains (SGP) facility in Kansas and Oklahoma. This data set includes observations from 19 locations. This data set covers the time period 1 October 2002 through 31 December 2009. Observations at several sites stopped during late 2009 see below for further information. Further information about the ARM SGP site is available at the following URL: http://www.arm.gov 1.1 Station Locations Site State Elev (m) Latitude Longitude Surface Type -------------------------------------------------------------------------------- E1_Larned KS 632 38.202 N 99.316 W Wheat E2_Hillsboro KS 450 38.306 N 97.301 W Grass E3_LeRoy KS 338 38.201 N 95.597 W Wheat and Soybeans (rotated) E4_Plevna KS 513 37.953 N 98.329 W Rangeland (ungrazed) E5_Halstead KS 440 38.114 N 97.513 W Wheat E6_Towanda KS 409 37.842 N 97.020 W Alfalfa E7_Elk Falls KS 283 37.383 N 96.180 W Pasture E8_Coldwater KS 664 37.333 N 99.309 W Rangeland (grazed) E9_Ashton KS 386 37.133 N 97.266 W Pasture E10_Tyro KS 248 37.068 N 95.788 W Alfalfa E11_Byron OK 360 36.881 N 98.285 W Alfalfa E12_Pawhuska OK 331 36.841 N 96.427 W Native Prairie E13_Lamont OK 318 36.605 N 97.485 W Pasture & Wheat E15_Ringwood OK 418 36.431 N 98.284 W Pasture E16_Vici OK 602 36.061 N 99.134 W Wheat E19_El Reno OK 421 35.557 N 98.017 W Pasture (ungrazed) E20_Meeker OK 309 35.564 N 96.988 W Pasture E22_Cordell OK 465 35.354 N 98.977 W Rangeland (grazed) E24_Cyril OK 409 34.883 N 98.205 W Wheat (gypsum hill) E27_Earlsboro OK 300 35.269 N 96.740 W Pasture Note: E19 has a slightly different location from the start of collection through 6 May 2003 (35.549 N and 98.020 W). From 7 May 2003 to the end of collection the location is as above. 1.2 Time Period Covered by Data All stations start collection on 1 October 2002 and end collection on 31 December 2009 except for: E1_Larned which stops on 14 October 2009. E2_Hillsboro which stops on 20 October 2009. E3_Le_Roy which starts on 23 October 2002 and stops on 28 October 2009. E5_Halstead which stops on 2 November 2009. E8_Coldwater which stops on 10 November 2009. E22_Cordell which stops on 1 December 2009. E24_Cyril which stops on 19 July 2007. E27_Earlsboro which starts on 6 August 2003 and stops on 4 December 2009. 1.3 Temporal Resolution All data are 60-minute resolution. See the instrumentation section for further information. 2.0 INSTRUMENTATION DESCRIPTION The ARM SGP soil measurements are from their Soil Water and Temperature System (SWATS) stations. All stations have soil moisture and soil temperature measurements at the -0.05, -0.15, -0.25, -0.35, -0.60, -0.85, -1.25 and -1.75 m heights except for the following: E5_Halstead no data at -1.25 m height. E10_Tyro no data at the -0.85, -1.25 or -1.75 m heights. E12_Pawhuska no data at the -0.85, -1.25 or -1.75 m heights. E13_Lamont no data at the -1.25 or -1.75 m heights. E20_Meeker no data at the -1.75 m height. E24_Cyril no data at the -1.75 m height. 2.1 General Information For complete information on the SWATS instrumentation see the ARM SMOS Handbook. Highlights are provided here. Sensors: At a typical SWATS site, sensors are installed at 8 different depths in the soil profile: 5, 15, 25, 35, 60, 85, 125, and 175 cm below the soil surface. Two profiles of sensors are installed at each site for replication and redundancy of measurements, resulting in a total of 16 sensors at each site. The two sensor profiles are located 1 m apart from each other. At several of the sites, however, rock or impermeable soil layers prohibitted the installation of sensors at the greater depths, resulting in less than 8 sensors in each profile. Installation: At each of the sites, all installation work was performed manually in order to minimize disturbance of the soil and vegetation at the site, and to minimize safety hazards. Sensors were placed in soil which had been disturbed as little as possible. This was accomplished by minimizing the amount of soil excavated, and by placing the sensors as far away from the excavated area as possible. This resulted in a relatively undisturbed profile of soil in which measurements are made. The electronics enclosure containing the electronic measurement equipment is mounted on a concrete slab placed on the ground surface in order to minimize the influence of the equipment on the SWATS sensors and on other instrument systems at the site. 2.2 Theory of Operation The Model 229L Matric Potential Sensor is designed to provide estimates of matric (or soil-water) potential. The sensor consists of a ceramic matrix, into which a hypodermic needle has been inserted. Inside the hypodermic needle are a thermocouple junction and a resistance heater. A rigid plastic body attaches the hypodermic needle to the ceramic matrix and secures the thermocouple and heater wiring. A sketch of the sensor is shown in the following Figure. The sensor operates on a heat dissipation principle. A heat pulse is generated by supplying an electrical current for a short time period to the resistance heater inside the sensor. Heat is dissipated by water held in the pore spaces. The temperature rise resulting from the heat pulse and subsequent dissipation of some of the heat is measured with the thermocouple junction inside the sensor. If the pore spaces contain much water, a large amount of heat can be dissipated and the temperature rise will be small. If the pore spaces contain little water and mostly air, the air acts as an insulator, little heat is dissipated, and a large temperature rise results. A calibration curve relates water potential to temperature rise. The calibration curve returns a water potential value based on the temperature rise reported by the sensor. In order to obtain an estimate of the volumetric water content of the soil, the water-holding characteristics of the soil must be known. The soil-water retention curve, also referred to as the water release curve or moisture characteristic curve, relates the water content to the water potential of the soil. This relationship is unique for each soil, and is a function of physical properties, such as soil particle-size distribution, organic-matter content, and compaction. Knowing this relationship, an estimate of water content can be made based on a value of water potential. The process by which temperature, water potential, and water content values are obtained is as follows: 1. Measure the initial sensor/soil temperature with the thermocouple 2. Introduce a heat pulse into the sensor by supplying a current to the resistance heater for a specified length of time 3. Turn off the heating current and measure the heated-sensor temperature 4. Calculate the sensor temperature rise by subtracting the initial temperature from the temperature after heating 5. Convert the sensor temperature rise into an estimate of soil water potential by applying a sensor calibration function 6. Convert the water potential estimate into an estimate of soil water content by applying a moisture characteristic function Sensor measurements are made and recorded at 1-hour intervals throughout the day. Each sensor reports the following information at each measurement interval: 1. initial sensor/soil temperature 2. sensor temperature rise (difference between after-heating and initial temperatures) 3. soil-water potential estimate 4. volumetric water content estimate. 2.3 Soil and Physical Characteristics EF1 / LARNED, KS Relatively flat site in an area with little relief. No landowner information concerning whether or not site has ever been plowed; some indications that it was plowed at some point. There is a wheat field directly south of the site, with several buildings and a cluster of trees several hundred meters to the north, and a U.S. highway 1/8 mile east. Relatively sparse and shallow root layer (density decreased visibly below ~ 10 cm) under thin short pasture. Very good site from a micrometeorological point of view. EF2 / HILLSBORO, KS Broad, relatively shallow slope, southern exposure, in an area with gently rolling hills. According to landowner, this site has never been plowed. Substantial sod layer, with roots visible through depth of access pits (65 cm); pasture more than hip deep in a wet year. Good micrometeorological site, with clumps of trees several hundred meters to the east and south. EF3 / LE ROY, KS Relatively flat site in an area with little relief. No landowner information concerning whether or not site has ever been plowed. Extremely dense and deep root layer, easily visible through depth of access pits; pasture more than hip deep. Very good micrometeorological site, with a few clumps of trees several hundred meters to the east and north, soybean field immediately to the south. EF4 / PLEVNA, KS Relatively flat site in an area with little relief. This is a sandy site, with thin clumps of vegetation at the surface (bare sand showing between), and a mix of flat water-smoothed stones. Unlikely that anyone would have ever plowed this site; few roots, and very little organic matter. Below about 70 cm, there were occasional bands of clay, but the layering is discontinuous between the two access pits. Good micrometeorological site, with significant lines of trees several hundred meters away in all directions except west. EF5 / HALSTEAD, KS Relatively flat site in an area with little relief. No landowner information concerning whether or not site has ever been plowed; some indication that it was plowed at some point. Medium density mixed grass and forb pasture, with roots visible through the depth of the access pits; winter wheat field to the south. Very good micrometeorological site, with a few sparse trees several hundred meters away to the north and west, south of an infrequently traveled gravel road. EF6 / TOWANDA, KS Seriously disturbed site in a region of irregular hills, with obvious evidence of terracing in the previous few years; thin layers of sandstone had been broken and strewn across the pasture in the process. System was installed on one shelf of the terraced field on a broad slope with southeast exposure. Soil in the two access holes differed in texture and color. Medium density pasture, hip deep, with roots visible through the depth of the access pits. Previously cultivated field to the south put into pasture in 1996. Not a good micrometeorological site due to the terrain variations. EF7 / ELK FALLS, KS Very flat site in a broad stream valley between irregularly rolling hills. No landowner information concerning whether or not site has ever been plowed; mix of good density "improved " pasture suggests that it has been disturbed to some degree. Roots visible through the depth of the access pits. Installation occurred after an extended dry period; large flat fissures, a couple of centimeters wide and tens of centimeters across, twisted irregularly down through the silt loam and silty clay soil, intersecting the access pits. Very good micrometeorological site, with clumps and lines of trees many hundreds of meters away. EF8 / COLDWATER, KS Relatively flat, sandy site with some gravel, in an area with only gentle relief. No landowner information concerning whether or not site has ever been plowed, but some indications that it was plowed at some time. Vegetation is relatively thin and clumpy, about knee deep, with bare soil showing. Roots were relatively thin. The hand-augered access holes (deeper than 85 cm) penetrated into sugar-like sand, pale and extremely dry. Very good micrometeorological site, with only a few trees at distance. EF9 / ASHTON, KS High, broad ridge with expansive view to the north. Pasture appears to have never been plowed (no landowner confirmation). There is a dramatic transition in soil texture and color between 60 cm and 85 cm below the surface that was not included in the soil characterization: soils become red and clayey, with red and white soft fragmented sandstone beneath that. Good quality, knee deep, dense mixed grass and forb pasture, with roots through the depth of the access pits. Micrometeorological data will be representative of conditions on the broad hilltop. EF10 / TYRO, KS Site located beside a man-made drainage ditch, with about 50 cm of mixed fill on top of the original ground level, in a relatively low area surrounded by higher hills. There is a layer of uneven, lumpy limestone at 55 cm below the SWATS system, varying as much as 15 cm in depth over an area 10 m in diameter, broken at the drainage ditch. Vegetation is hip deep, with roots reaching to the rock layer. The sensors are at 5, 15, 25, 35, and 55 cm, with the 55 cm sensors positioned immediately adjacent to the rock layer. There is a cultivated field (usually winter wheat) south of the drainage ditch. Micrometeorological data will be representative of conditions in the valley. EF11 / BYRON, OK Very flat site in a wide, low area, with a few dune-shaped small hills to the far south and east. Proved to be the local low spot: hand augering hit the water table during installation, with the 125 cm and 175 cm sensors installed under water. Since installation, this site has flooded repeatedly. Relatively dense, knee-deep pasture with roots visible through the depth of the access pits. Cultivated pasture to the south, either alfalfa or winter wheat. Very good micrometeorological site. EF12 / PAWHUSKA, OK Broad ridge in the Tallgrass Prairie Preserve, a few hundred meters north of the Oklahoma Mesonet Foraker site (http://okmesonet.ocs.ou.edu/). The ground drops sharply several hundred meters north of the Extended Facility, and the pasture has never been plowed. There are irregular rock horizons at this location, with a broken layer of shale about 45 cm down, and fractured, increasingly dense sandstone below that. Sensors were install at 5, 15, 25, 35, and 60 cm. Grazing and fire permitting, the tallgrass can reach heights of several meters here, and roots were thick down to the rock. Micrometeorological data will be representative of conditions on the broad hilltop. EF13 / LAMONT, OK (CENTRAL FACILITY) Broad hilltop, a few hundred meters west of a valley. The pasture had been terraced to some degree and "improved" several decades previously, but has returned to a more native mix of grasses and forbs. Vegetation is greater than hip deep (if ungrazed), and roots were visible through the depth of the access pits. A layer of sandstone begins 88 cm below the surface, so sensors are installed at depths of 5, 15, 25, 35, 60, and 85 cm. The original installation in January- February 1996 only included the top five levels, due to extremely dry conditions; the lowest depth (85 cm) was added in February 1997. Micrometeorological data will be representative of conditions on the broad hilltop. EF15 / RINGWOOD, OK Sandy site, in a relatively uniform area that appears to be grass-covered sand dunes, with tree lines several hundred meters to the north, west, and south. Site appears to have never been plowed (no landowner confirmation). Soil from the deepest two levels (125 cm and 175 cm) was different in texture, with some clay content. Vegetation is knee deep and covers the ground more completely than at the other two sandy sites; roots were visible through the depth of the access pits. Micrometeorological data will be representative of the area. EF16 / VICI, OK Relatively flat site, with a slight slope to the north leading to a tree-filled gully. Wheat field to the south has been terraced, so is possible that this site was disturbed at some time. Vegetation is knee deep and tends to be clumpy, with soil occasionally showing between clumps; roots were visible through the depth of the access pits. Good micrometeorological site. EF19/ EL RENO, OK Relatively flat site, in gently rolling terrain. Unplowed tallgrass prairie, with a few buildings several hundred meters to the south. Grazing and fire permitting, the tallgrass can reach heights of several meters here, and roots were visible through the depth of the access pits. Good micrometeorological site. This site is collocated or in proximity with several other networks: 1.6 km from the Oklahoma Mesonet El Reno site (http://okmesonet.ocs.ou.edu/); co-located with the USDA ARS SHAWMS (site ER01, http://grl.ars.usda.gov); and co-located with the USDA NRCS National Water & Climate Center?s Soil Climate Analysis Network (site 2022, http://www.wcc.nrcs.usda.gov/scan/). EF20 / MEEKER, OK Broad, north-south ridge in a hilly area, with outcrops of sandstone along the ridgeline. The field has been plowed at some point. The SWATS system is located to the west of the ridge, in an area where the first layer of sandstone is about 130 cm below the surface. There are seven sensors in each profile at this site, lacking the 175 cm depth. When ungrazed, vegetation is knee to hip deep; roots were visible through the depth of the access pits. Micrometeorological data will be representative of conditions on the ridgeline. EF22 / CORDELL, OK Gently slope with southern exposure, in slightly rolling terrain, with a few trees and buildings several hundred meters to the north, and a busy U.S. highway to the east. No landowner information available concerning whether or not site has ever been plowed. Vegetation is a knee deep when ungrazed, a bit sparse with bare soil showing between clumps; roots were visible through the upper half of the access pits. Good micrometeorological site. Note: the highway is now much closer to the SWATS than when originally installed, approximately 30 m east of the system; the rest of the Extended Facility has been moved further west. EF24 / CYRIL, OK Gypsum knoll, with a county road on the north edge, surrounded by wheat fields. The sensors are located near the southwest edge of the knoll, in a "hole" in the gypsum filled with soil. The gypsum extends under the wheat field south of the site for less than 10 meters south of the Extended Facility, so soil moisture measurements will probably not be representative of conditions in the surrounding fields. The installation is non-standard in sensor placement, but does have two sensors at all depths except 175 cm. Vegetation on the knoll is a mix of cacti and opportunistic grasses and forbs. Micrometeorological data will be representative of mixed conditions over the knoll and the surrounding wheat fields. EF27 / EARLSBORO, OK No information available. 3.0 DATA COLLECTION AND PROCESSING 3.1 ARM Data Collection and Processing Full information on the ARM SWATS data collection and processing is available in the ARM SWATSS Handbook. Highlights are provided here. 3.2 UCAR/JOSS Data Processing The University Corporation for Atmospheric Research/Joint Offfice for Science Support (UCAR/JOSS) converted the data from the raw format provided by ARM into the CEOP EOP-3 data format agreed to by the CEOP Scientific Steering Committee. This format is described in detail as part of the CEOP Reference Site Data Set Procedures Report which is available at the following URL: http://www.joss.ucar.edu/ghp/ceopdm/refdata_report/ceop_soils_format.html The hourly values from ARM were used without change. 4.0 QUALITY CONTROL PROCEDURES 4.1 ARM Quality Control Procedures For detailed information on SWATS quality control procedures please see the ARM SWATS Handbook. 4.2 UCAR/JOSS Quality Control Procedures UCAR/JOSS converted the ARM QC flags into the CEOP QC flags in the following manner. If a parameter failed one of the ARM QC checks it was flagged as Questionable/Dubious ("D") and if it failed two or more ARM QC checks it was flagged as Bad ("B"). Additionally, UCAR/JOSS conducted two primary quality assurrance/control procedures on the reference site data. First the data has been evaluated by a detailed QA algorithm that verifies the format is correct, examines any QC flags, and conducts basic checks on data values. Second, JOSS conducts a manual inspection of time series plots of each parameter. 5.0 GAP FILLING PROCEDURES No gap filling procedures were applied to these data by either ARM or UCAR/JOSS. 6.0 DATA REMARKS None. 7.0 REFERENCE REQUIREMENTS To support the continuation of this program, please include the following 'credit line' in the acknowledgments of your publication: "Data were obtained from the Atmospheric Radiation Measurement (ARM) Program sponsored by the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research, Environmental Sciences Division." 8.0 REFERENCES Further information on ARM SGP SWATS instrumentation (including QC, calibration, maintenance, theory of operation, and references) can be found in the ARM SWATS Handbook.