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Data Set ID:
SV12PSMF

SMAPVEX12 Probe-Based In Situ Soil Moisture Data for Forest Area, Version 1

This data set contains in situ soil moisture data collected at several forested sites as a part of the Soil Moisture Active Passive Validation Experiment 2012 (SMAPVEX12).

Geographic Coverage

Parameter(s):
  • Soils > Electrical Conductivity > Dielectric Constant
  • Soils > Soil Depth
  • Soils > Soil Temperature
  • Soils > Soil Moisture/Water Content > Volumetric Soil Moisture (Fraction)
Spatial Coverage:
  • N: 49.96, S: 49.44, E: -97.85, W: -98.51

Spatial Resolution:
  • 100 m x 100 m
Temporal Coverage:
  • 7 June 2012 to 13 July 2012
Temporal Resolution: 1 day to 8 day
Data Format(s):
  • Microsoft Excel
Platform(s) FIELD SURVEYS
Sensor(s): SOIL MOISTURE PROBE, SOIL TEMPERATURE PROBE
Version: V1
Data Contributor(s): Mahta Moghaddam, Aaron Berg
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.

Moghaddam, M. and A. Berg. 2014. SMAPVEX12 Probe-Based In Situ Soil Moisture Data for Forest Area, Version 1. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi: http://dx.doi.org/10.5067/2ETTBINRTSKX. [Date Accessed].

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Notice: 

The documentation for this data set was provided solely by the Principal Investigator(s), and was not further developed, thoroughly reviewed, or edited by NSIDC. Thus, support for this data set may be limited.

Detailed Data Description

This data set contains in situ soil moisture data collected at several forested sites as a part of the Soil Moisture Active Passive Validation Experiment 2012 (SMAPVEX12).

Format

Data are provided in a Microsoft Excel file containing one worksheet per site: F1, F2, F3, F5. Table 1 describes the soil sampling data columns of the data file, SV12PSMF_SMAPVEX_SoilDATA_final_03142013.xlsx.

Table 1. Data Fields and Descriptions
Column Heading Description
DATE Date of the samples
SITE ID ID of the forest site (F1, F2, F3 or F5)
LOC ID ID of the sample location
LAT Latitude of the sampling location
LON Longitude of the sampling location
SOIL D1 Depth of the organic layer in inches: corner 1
SOIL D2 Depth of the organic layer: corner 2
SOIL D3 Depth of the organic layer: corner 3
SOIL D4 Depth of the organic layer: corner 4
SM1 Volumetric soil moisture: sample 1
SM2 Volumetric soil moisture: sample 2
SM3 Volumetric soil moisture: sample 3
Probe Type Type of the soil moisture probe (Hydra or Theta Probe)
T0 Surface temperature measurement in degrees Celsius
T5 Temperature measurement at 5 cm depth in degrees Celsius
T10 Temperature measurement at 10 cm depth in degrees Celsius
EPS REAL1 Real part of dielectric constant for the soil moisture sample 1
EPS IMAG1 Imaginary part of dielectric constant for the soil moisture sample 1
EPS REAL2 Real part of dielectric constant for the soil moisture sample 2
EPS IMAG2 Imaginary part of dielectric constant for the soil moisture sample 2
EPS REAL3 Real part of dielectric constant for the soil moisture sample 3
EPS IMAG3 Imaginary part of dielectric constant for the soil moisture sample 3

Missing data are represented by a blank [ ] or by NaN.

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File and Directory Structure

Data files are available on the HTTPS site in the https://n5eil01u.ecs.nsidc.org/SMAP_VAL/SV12PSMF.001/ directory.

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File Naming Convention

SV12PSMF_SMAPVEX_SoilDATA_final_03142013.xlsx

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File Size

The data file is approximately 72 KB.

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Spatial Coverage

Southernmost Latitude: 49.44°N
Northernmost Latitude: 49.96°N
Westernmost Longitude: 98.51°W
Easternmost Longitude: 97.85°W

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Temporal Coverage and Resolution

Measurements were taken every one to eight days from 07 June 2012 through 13 July 2012.

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Parameter or Variable

Parameters in this data set include volumetric soil moisture, and both the real and imaginary part of the dielectric constant. The following table describes the units of measurement and sources of each parameter.

Table 2. Parameter Units and Sensors
Parameter Unit of Measurement Sensor
Volumetric soil moisture Water Fraction Volume (m3/m3) Hydra Probe II
Soil temperature Celsius Thermometer
Dielectric constant (real and imaginary part) Unitless Hydra Probe II
Depth of the organic layer Inch Measuring Stick

Parameter Range

Valid parameter values are as follows: 
Volumetric soil moisture: 0 - 0.6 m3/m3 
Soil temperature: 0 - 30°C 
Real part of the dielectric constant: 0 - 110
Depth of the organic layer: 0 - 30 in

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Spatial Resolution

For each site, sampling was performed on two orthogonal transects within a circle of approximately 100 m radius.

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Projection

Data are provided in Universal Transverse Mercator (UTM) World Geodetic System 1984 (WGS84) coordinates.

Grid Description

No grid.

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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 Microsoft Excel is recommended.

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Data Acquisition and Processing

Theory of Measurements

Section Sampling

The soil and vegetation sampling approaches used for the agriculture cropland and forest sites was different, due to the inherent differences in the characteristics of these landscapes, the measurement strategies for forests and crops, and the ease of access to the sites.

One sample site was located in each of the four forest sites and was chosen to be representative of the heterogeneity of the site. The observation area for both soil moisture and vegetation sampling within each site consisted of two orthogonal transects within a circle of 100 m radius (Fig. 3). Each of the nine sampling points was spaced 50 m apart. Points were flagged and their GPS coordinates were determined at the beginning of the campaign to facilitate navigation back to each point.

Figure 1 shows a map of the forest sites.

Map of Forest Study Sites
Figure 1. Map of Forest Study Sites (Site ID F1, F2, F3, F5)

Figure 2 shows a schematic diagram of sample locations (Location ID) within the forest sites:

Sample Locations
Figure 2. Schematic diagram of sample locations (Location ID) within the forest sites.

Organic soil thickness was determined at four corners of a 10 inch quadrant, see below:

Site Soil Sampling
Figure 3. Schematic diagram of sample locations (Location ID) within the forest sites.

See more details in section 2.1.1 of the SMAPVEX12 Database Report, released 18 December 2012.

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Sensor or Instrument Description

Investigators used the Stevens Hydra Probe II to measure surface volumetric soil moisture.

Hydra Probes

Hydra Probes are based on coaxial impedance dielectric reflectometry. The probes were connected to a PDA. They use an oscillator to generate an electromagnetic signal at 50 MHz that is propagated through three metal tines into the soil. The part of the signal that is reflected back to the unit is measured in volts and is used to numerically solve Maxwell's equations, to calculate the impedance and the real and imaginary dielectric permittivity.

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Processing Steps

Calibration of the Probe Measurements

Similar to the agricultural fields a unique calibration curve (R2=.798, p<0.05, n=37) was developed between the volumetric cores obtained from the forest sites and the Steven's Hydra Probe soil moisture measurements obtained at the same location. Points which fell outside 1.5 times the standard deviation of the difference between the core and the probe measured soil moisture were determined to be outliers and removed from the data set. A leave-one-out validation was conducted (Rowlandson et al. 2013) and indicated that the calibration equation was robust. The RMSE of the developed equation was .058 m3m-3, a RMSE greater than that determined in agricultural fields. It is anticipated that the higher RMSE was due to the complications of obtaining soil samples (and probe readings) over these sites due the amount of litter material in the soils.

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Error Sources

The RMSE of the developed calibration equation was .058 m3m-3, a RMSE greater than that determined in agricultural fields. It is anticipated that the higher RMSE was due to the complications of obtaining soil samples (and probe readings) over these sites due the amount of litter material in the soils.

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References and Related Publications

Contacts and Acknowledgments

Mahta Moghaddam
Department of Electrical Engineering
University of Southern California
3737 Watt Way
Los Angeles, CA 90089, USA
e-mail: mahta@usc.edu
phone: +1 213.740.4712

Aaron Berg
Department Geography
University of Guelph
Guelph, ON, N1G 2W1, Canada
e-mail: aberg@uoguelph.ca 
phone: +1 519.824-4120

Acknowledgments: 

Agriculture and Agri-Food Canada, National Aeronautics and Space Administration, U.S. Department of Agriculture, Environment Canada, University of Manitoba, University of Guelph, Massachusetts Institute of Technology (MIT), University of South Carolina, University of Colorado, University of Sherbrooke, Ohio State, University of Montana, Florida International University, University of Southern California, Texas A&M, Georgia Institute of Technology, University of Washington are acknowledged for their support for the campaign.

Field Sampling Team

Mariko Bürgin (University of Southern California)
Vanessa Escobar (NASA Goddard)
Alexandra Konings (MIT)
Parag Narvekar (MIT)
Stacie Westervelt (University of Winnipeg)
Kaighin McColl (MIT)
Alan Rich (University of Winnipeg)
Jennifer Watts (University of Montana)
Hoda Jafarian (University of Sherbrooke)
Matt Jones (University of Montana)
Mehdi Hosseini (University of Sherbrooke)
Dominik Schneider (University of Colorado)
Karel Janik (University of Sherbrooke)
Maheshwari Neelam (Texas A&M)
Steven Chan (NASA JPL)
Ramata Magagi (University of Sherbrooke)
Maria Abrahamowicz (Environ. Canada)
Mike Cosh (USDA)
Najib Djamai (University of Sherbrooke)

Document Information

DOCUMENT CREATION DATE

October 2013

DOCUMENT REVISION DATE

N/A

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