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: mccordra@ornl.gov
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.