Data Set ID: 
CL07SM

CLASIC07 In Situ Soil Moisture Data, Version 1

This data set is comprised of several parameters from in situ measurements collected for the Cloud and Land Surface Interaction Campaign 2007 (CLASIC07).

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Parameter(s):
  • Soils > Electrical Conductivity
  • Soils > Soil Temperature > Land Surface Temperature
  • Soils > Soil Bulk Density
  • Soils > Soil Temperature
  • Soils > Soil Moisture/Water Content > Volumetric Soil Moisture (Fraction)
Spatial Coverage:
  • N: 35.21, S: 34.91, E: -97.95, W: -98.59

Spatial Resolution:
  • 0.8 km x 0.8 km
Temporal Coverage:
  • 7 June 2007 to 7 July 2007
Temporal Resolution: 1 day to 2 days
Data Format(s):
  • ASCII Text
Platform(s) FIELD SURVEYS
Sensor(s): SOIL SAMPLER, SOIL TEMPERATURE PROBE
Version: V1
Data Contributor(s): Cosh, M.

Data Citation

As a condition of using these data, you must cite the use of this data set using the following citation. For more information, see our Use and Copyright Web page.

Cosh, M. 2013. CLASIC07 In Situ Soil Moisture Data, Version 1. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi: https://doi.org/10.5067/W2WMLRUQOCA8. [Date Accessed].

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Detailed Data Description

This data set is comprised of several parameters from in situ measurements collected for the Cloud and Land Surface Interaction Campaign 2007 (CLASIC07). The study site was divided into regional squares, approximately .08 km by .08 km in size, with several sample point locations.

Format

Data are provided in tab-delimited ASCII text files. An associated Extensible Markup Language (XML) metadata file is also provided for each data file.

The following table describes the soil sampling data columns of the data file, GVSM_LW_FC.txt.

Table 1. Data Fields and Descriptions
Column Heading Description
Date Month/Day/Year
DOY Day of the year
Site_ID Designation of the field site
Sample Sample number
Start Time Hour:Minute
Lat Latitude
Lon Longitude
UTM Universal Transverse Mercator
EG Temperature of exposed ground surface [°C]
SG Temperature of ground surface in shadow [°C]
EV Temperature of exposed vegetation surface [°C]
SV Temperature of vegetation surface in shadow [°C]
Temp_1cm Soil temperature at depth 1cm [°C]
Temp_5cm Soil temperature at depth 5cm [°C]
Temp_10cm Soil temperature at depth 10cm [°C]
mV-A Theta probe reading A [mV]
mV-B Theta probe reading B [mV]
mV-C Theta probe reading C [mV]
TP_gc_A Theta probe soil moisture value A with general calibration [%]
TP_gc_B Theta probe soil moisture value B with general calibration [%]
TP_gc_C Theta probe soil moisture value C with general calibration [%]
TP_fsc_A Theta probe soil moisture value A with field specific calibration [m3/m3]
TP_fsc_B Theta probe soil moisture value B with field specific calibration [m3/m3]
TP_fsc_C Theta probe soil moisture value C with field specific calibration [m3/m3]
Can_ID_0-6 Identification number of the soil core sampling can
Can_Wgt_0-6 Weight of the soil core sampling can
Wet_Wgt_0-6 Wet weight of the soil core sample [g]
Dry_Wgt_0-6 Dry weight of the soil core sample [g]
Soil_BD_0-6 Bulk density of soil core sample [g/cm3]
VSM_0-6 Volumetric soil moisture obtained from the soil core sample [m3/m3]
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File and Directory Structure

Data files are available at: 

https://n5eil01u.ecs.nsidc.org/SMAP_VAL/CL07SM.001/

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File Naming Convention

CL07SM_GVSM_LW_FC.txt contains the soil moisture data for the study areas, Little Washita (LW) and Fort Cobb (FC).

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File Size

The data file is approximately 502 KB.

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Spatial Coverage

Southernmost Latitude: 34.91°N
Northernmost Latitude: 35.21°N
Westernmost Longitude: 98.59°W
Easternmost Longitude: 97.95°W

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Spatial Resolution

Sampling was performed on sites approximately one quarter section (0.8 km by 0.8 km) in size.

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Projection

Universal Transverse Mercator (UTM) Zone 14N easting and northing, and World Geodetic System 1984 (WGS84) coordinates.

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Temporal Coverage and Resolution

Depending on the site and period, measurements were taken every 1 to 2 days from 7 June 2007 through 7 July 2007.

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Parameter or Variable

Parameters include volumetric soil moisture (m3/m3 or %), surface and soil temperature (°C), bulk density (g/cm3), and electrical conductivity [mV].

Parameter Range

Valid parameter values are as follows:

Volumetric Soil Moisture: 0 - 0.6 m3/m3
Surface and Soil Temperature: 0 - 50°C
Bulk Density: 1.57 g/cm3 (maximum)
Electrical Conductivity: 1.135 mV (maximum)
Missing Data: NaN

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Software and Tools

No special tools are required to view these data. A spreadsheet program which recognizes tab-delimited text files, such as MS Excel is recommended. Any word-processing program or Web browser will also display the data.

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Data Acquisition and Processing

Theory of Measurements

Section Sampling

Sampling was performed on sites approximately one quarter section (0.8 km by 0.8 km) in size. Eight points were sampled in a field for Theta Probe volumetric soil moisture and voltage measurements. Two points were sampled in a field for surface and soil temperature, and for soil moisture samples.

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Sensor or Instrument Description

Theta Probes

Investigators used theta probes to measure surface volumetric soil moisture. The probes were Type ML2 manually-operated impedance instruments manufactured by Delta-T Devices, Ltd. The theta probes have 4 separate 6-cm stainless steel rods inserted vertically into the soil. Each instrument was connected to a handheld reader, which delivers the electrical pulse, detects the return signal, and converts the period to a voltage between 0 V and about 1 V. Watershed surface soil moisture was sampled each morning (9:00AM-12:00AM) during the experiment.

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Processing Steps

Soil Moisture Sample Processing

Researchers weighed the wet soil obtained in the field, heated the soil in an oven to dry it, and then weighed the dry soil.

Calibration of Probe Measurements

The software provided by the probe manufacturer calibrates the theta probes by calculating an estimate of volumetric soil moisture according to Equation 1:

Theta=(1.07+6.4*V-6.4*V2+4.7*V3-a0)/a1 (Equation 1)

where a0 and a1 are 1.6 and 8.4, respectively. These estimates are provided in the data files.

Researchers also performed field-specific calibration for each sampled field. Soil moisture values obtained using the gravimetric sampling technique were compared with the theta probe readings of the corresponding locations. A regression relationship was developed, and revised volumetric soil moisture values were estimated for the theta probe measurements.

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Error Sources

Error sources for theta probe soil moisture include instabilities in electronics and calibration coefficients. Errors regarding temperature sensors occur due to instabilities in electronics.

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Quality Assessment

The field-specific calibration of the soil moisture values using the soil core samples ensures high accuracy and minimized the potential errors.

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References and Related Publications

Contacts and Acknowledgments

Michael H. Cosh
United States Department of Agriculture - Agricultural Research Service (USDA ARS)
Hydrology and Remote Sensing Laboratory
10300 Baltimore Avenue
Bldg. 007, Rm. 104
BARC-West
Beltsville, MD 20705

Document Information

DOCUMENT CREATION DATE

June 2015

DOCUMENT REVISION DATE

N/A

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