SMEX03 Regional Ground Soil Moisture Data: Georgia
Summary
The parameters for this data set include gravimetric soil moisture, volumetric soil moisture, bulk density, and surface and soil temperature for the Georgia study region. This data set is part of the Soil Moisture Experiment 2003 (SMEX03). The United States portion of SMEX03 was conducted during June and July, 2003. Data are provided in a tab-delimited ASCII text file, and are available via FTP.
These data were collected as part of a validation study for the Advanced Microwave Scanning Radiometer - Earth Observing System (AMSR-E). AMSR-E is a mission instrument launched aboard NASA's Aqua Satellite on 04 May 2002. AMSR-E validation studies linked to SMEX are designed to evaluate the accuracy of AMSR-E soil moisture data. Specific validation objectives include assessing and refining soil moisture algorithm performance; verifying soil moisture estimation accuracy; investigating the effects of vegetation, surface temperature, topography, and soil texture on soil moisture accuracy; and determining the regions that are useful for AMSR-E soil moisture measurements.
Citing These Data
The following example shows how to cite the use of this data set in a publication. For more information, see our Use and Copyright Web page.
Bosch, D., T. J. Jackson, V. Lakshmi, and J. Jacobs. 2006. SMEX03 Regional Ground Soil Moisture Data: Georgia. Boulder, CO USA: National Snow and Ice Data Center. Digital media.
Overview Table
| Category | Description |
|---|---|
| Data format | Tab-delimited ASCII text |
| Spatial coverage | Southernmost Latitude: 31.20º N |
| Temporal coverage | 23 June 2003 to 2 July 2003 |
| File naming convention | GA_GVSM_Raw.txt |
| File size | approximately 247 KB |
| Parameter(s) | Gravimetric and volumetric soil moisture, bulk density, surface and soil temperature |
| Procedures for obtaining data | Data are available via FTP. |
Table of Contents
1. Contacts and Acknowledgments
2. Detailed Data Description
3. Data Access and Tools
4. Data Acquisition and Processing
5. References and Related Publications
6. Document Information
1. Contacts and Acknowledgments
Investigator(s)
David Bosch
Southeast Watershed Research Laboratory
US Department of Agriculture (USDA) - Agricultural Research Service
(ARS)
Tifton, GA 31794
USA
Thomas J. Jackson
Hydrology and Remote Sensing Laboratory
US Department of Agriculture (USDA) - Agricultural Research Service
(ARS)
Beltsville, MD 20705
USA
Venkat Lakshmi
University of South Carolina
Columbia, SC 29208
USA
Jennifer Jacobs
University of New Hampshire
Durham, NH 03824
USA
Technical Contact
NSIDC User Services
National Snow and Ice Data Center
CIRES, 449 UCB
University of Colorado
Boulder, CO 80309-0449 USA
phone: +1 303.492.6199
fax: +1 303.492.2468
form: Contact NSIDC User Services
e-mail: nsidc@nsidc.org
Acknowledgements
Many graduate students and volunteers worked to collect the field data. The investigators thank the SMEX03 Science Team, the staff of the Southeast Watershed Research Lab, graduate students from the University of South Carolina and the University of Georgia, Scientists from the NASA Goddard Space Flight Center, and scientists from the United States Department of Agriculture - Agricultural Research Service (USDA-ARS) National Soil Tilth Lab for their critical roles in data collection. The investigators also thank NASA for their generous contributions to the study. This work was supported by the NASA Aqua AMSR, Terrestrial Hydrology and Global Water Cycle Programs.
2. Detailed Data Description
Format
The data are in a tab-delimited ASCII text file. Missing data are represented with -999 in the data file. The column headings and the information in each column are described in the following table. See the Parameter or Variable section for more information about the parameters.
Column Heading in File |
Description |
|---|---|
| Site ID | Site location identifier number |
| Date | Month/day/year |
| Crop_type | Type of land cover: |
| Sample_Time (EDT) | Sampling time in Eastern Daylight Time (EDT); most sampling is 5-10 minutes in duration |
| Latitude WGS84 | Latitude of sample site in decimal degrees, World Geodetic System 1984 (WGS84) |
| Longitude WGS84 | Longitude of sample site in decimal degrees, WGS84 |
| Easting in m WGS84 Zone 17 | Easting of sample site in meters, WGS84, Zone 17 |
| Northing in m WGS84 Zone 17 | Northing of sample site in meters, WGS84, Zone 17 |
| TP_V row | Impedance probe (ThetaProbe) millivolt reading in V in row |
| TP_V 1/4 row | ThetaProbe millivolt reading in V at ¼ row |
| TP_V 1/2 row | ThetaProbe millivolt reading in V at ½ row |
| TP_gc row | ThetaProbe volumetric soil moisture (VSM) in m3/m3, from general calibration in row |
| TP_gc 1/4 row | ThetaProbe VSM in m3/m3 from general calibration at ¼ row |
| TP_gc 1/2 row | ThetaProbe VSM in m3/m3 from general calibration at ½ row |
| TP_ssc row | ThetaProbe VSM in m3/m3 from site-specific calibration in row |
| TP_ssc 1/4 row | ThetaProbe VSM in m3/m3 from site-specific calibration at ¼ row |
| TP_ssc 1/2 row | ThetaProbe VSM in m3/m3 from site-specific calibration at ½ row |
| TP_V average | ThetaProbe volt reading, average |
| TP_V stdev | ThetaProbe volt reading, standard deviation |
| TP_gc average | ThetaProbe volumetric soil moisture from general calibration, average |
| TP_gc stdev | ThetaProbe volumetric soil moisture from general calibration, standard deviation |
| TP_ssc average | ThetaProbe volumetric soil moisture from site-specific calibration, average |
| TP_ssc stdev | ThetaProbe volumetric soil moisture from site-specific calibration, standard deviation |
| ST_C 1 cm | Soil temperature in degrees Celsius at 1 cm |
| ST_C 5 cm | Soil temperature in degrees Celsius at 5 cm |
| ST_C 10 cm | Soil temperature in degrees Celsius at 10 cm |
| Surf_Temp C | Surface temperature in degrees Celsius |
| Can_ID 0-1 cm | Soil can identifier for 0-1 cm sample |
| Can_Wgt 0-1 cm | Soil can weight for 0-1 cm sample |
| Wet_Wgt 0-1 cm | Wet weight of soil for 0-1 cm sample |
| Dry_Wgt 0-1 cm | Dry weight of soil for 0-1 cm sample |
| GSM 0-1 cm | Gravimetric soil moisture in g/g for 0-1 cm sample |
| BD 0-1 cm | Bulk density in g/cm3 for 0-1 cm sample |
| VSM 0-1 cm | Volumetric soil moisture (calculated from sample) in m3/m3 for 0-1 cm sample |
| Can_ID 0-3 cm | Soil can identifier for 0-3 cm sample |
| Can_Wgt 0-3 cm | Soil can weight for 0-3 cm sample |
| Wet_Wgt 0-3 cm | Wet weight of soil for 0-3 cm sample |
| Dry_Wgt 0-3 cm | Dry weight of soil for 0-3 cm sample |
| GSM 0-3 cm | Gravimetric soil moisture in g/g for 0-3 cm sample |
| BD 0-3 cm | Bulk density in g/cm3 for 0-3 cm sample |
| VSM 0-3 cm | Volumetric soil moisture (calculated from sample) in m3/m3 for 0-3 cm sample |
| Can_ID 3-6 cm | Soil can identifier for 3-6 cm sample |
| Can_Wgt 3-6 cm | Soil can weight for 3-6 cm sample |
| Wet_Wgt 3-6 cm | Wet weight of soil for 3-6 cm sample |
| Dry_Wgt 3-6 cm | Dry weight of soil for 3-6 cm sample |
| GSM 3-6 cm | Gravimetric soil moisture in g/g for 3-6 cm sample |
| BD 3-6 cm | Bulk density in g/cm3 for 3-6 cm sample |
| VSM 3-6 cm | Volumetric soil moisture (calculated from sample) in m3/m3 for 3-6 cm sample |
| VSM 0-6 cm | Total volumetric soil moisture in m3/m3 for 0-6 cm |
| rain/irrig (mm) | Notes about amount of rain the previous night (if any); whether or not the field was irrigated, etc. |
File Naming Convention
The single data file is named GA_GVSM_Raw.txt.
File Size
The data file is approximately 247 KB.
Spatial Coverage
Southernmost Latitude: 31.20º N
Northernmost Latitude: 31.82º N
Westernmost Longitude: 83.94º W
Easternmost Longitude: 83.43º W
Temporal Coverage
Data were collected from 23 June 2003 to 2 July 2003.
Temporal Resolution
Data were collected once daily at multiple sites. The sampling was conducted between 11:30 A.M. and 3:00 P.M. local time. Most sampling was 5 to 10 minutes in duration.
Parameter or Variable
Parameter Description
Parameters in this data set are gravimetric soil moisture (GSM), volumetric soil moisture (VSM), bulk density (BD), and surface and soil temperature. The following table describes the units of measurement and sources of each parameter.
| Parameter | Units of Measurement | Source/Sensor(s) |
|---|---|---|
| Gravimetric soil moisture | Grams of water per grams of dry soil | Manual soil collection |
| Volumetric soil moisture | Cubic meters of water per cubic meters of dry soil | Manual soil collection and impedance probes (ThetaProbes) |
| Bulk density | Grams per cubic centimeter (g/cm3) | Manual soil collection |
| Surface and soil temperature | Degrees Celsius | Infrared thermometers, temperature probes |
Sample Data Record
The following sample illustrates the data. The first 12 data rows are shown; only the first 4 columns and last 4 columns of each row are shown (the column headings in the sample indicate the included columns). Missing data are represented with -999 or -99:99 in the data file.
Site ID |
Date |
Crop_type |
Sample_Time (EDT) |
... |
BD 3-6 cm |
VSM 3-6 cm |
VSM 0-6 cm |
rain/irrig (mm) |
|
GA01 |
6/23/2003 |
peanuts |
-99:99 |
... |
1.479 |
0.12 |
0.115 |
nd |
|
GA01 |
6/24/2003 |
peanuts |
-99:99 |
... |
1.386 |
0.101 |
0.08 |
0 |
|
GA01 |
6/25/2003 |
peanuts |
-99:99 |
... |
1.37 |
0.092 |
0.076 |
0 |
|
GA01 |
6/26/2003 |
peanuts |
14:00 |
... |
1.531 |
0.108 |
0.09 |
nd |
|
GA01 |
6/27/2003 |
peanuts |
13:35 |
... |
1.609 |
0.102 |
0.075 |
0 |
|
GA01 |
6/28/2003 |
peanuts |
13:50 |
... |
1.279 |
0.091 |
0.057 |
0 |
|
GA01 |
6/29/2003 |
peanuts |
13:18 |
... |
1.395 |
0.09 |
0.091 |
1 |
|
GA01 |
6/30/2003 |
peanuts |
13:32 |
... |
1.382 |
0.087 |
0.089 |
3 |
|
GA01 |
7/1/2003 |
peanuts |
13:38 |
... |
1.487 |
0.099 |
0.098 |
5 |
|
GA01 |
7/2/2003 |
peanuts |
13:43 |
... |
1.425 |
0.139 |
0.139 |
21 |
|
GA02 |
6/23/2003 |
forest |
11:50 |
... |
1.547 |
0.094 |
0.104 |
nd |
|
GA02 |
6/24/2003 |
forest |
13:34 |
... |
1.309 |
0.096 |
0.095 |
0 |
Error Sources
Impedance Probes
Impedance probes (ThetaProbes) were used for volumetric soil moisture sampling. For various reasons, including extremely dry conditions, severe weather restrictions, miscommunication among personnel, and cultivation, some sites were not sampled on particular days. Occasionally, a ThetaProbe rod was broken because of very hard and dry soil conditions. When possible, the broken rod was replaced. When it was not possible to replace the rod, a new instrument was used. The site-specific calibration resulted in an average root mean square error of 0.02 m3/m3.
Bulk Density
The coring tool extracts a known volume of soil that is used to compute a bulk density. There is potential for compaction with this tool, which results in higher bulk densities when compared to other methods. For the 0-1 cm sample, and for the other sample depths when dry moisture conditions prevented using the coring tool, a 13 cm x 10 cm x 2 cm rectangular shaped scoop tool was used to retrieve the soil sample. This tool does not allow for a bulk density estimate, so the average bulk density from all coring tool samples was used for computation of volumetric soil moisture. Also, the bulk density of the 0-3 cm sample was considered less reliable than the 3-6 cm sample; therefore, the 3-6 cm bulk density was used for all calculations. The bulk density for all 0-1 cm samples was assumed to be 1.5 g/cm3.
3. Data Access and Tools
Data Access
Data are available via FTP.
Volume
The total volume is approximately 247 KB.
Related Data Collections
See related information on the NSIDC Soil Moisture Experiment (SMEX) Web site.
4. Data Acquisition and Processing
Theory of Measurements
This regional soil moisture site is within a single Aqua satellite passive microwave footprint (approximately 50 km), and measurements were taken around the time of the AMSR-E/Aqua overpass (13:30 local time). The goal of soil moisture sampling in these regional sites is to provide a reliable estimate of volumetric soil moisture and variance within the AMSR-E footprint.
Sampling
Sampling was performed on sites approximately one quarter section (0.8 km by 0.8 km) in size. A grid of 49 individual sites was sampled, covering approximately 50 km by 75 km. One location in each of the sites was sampled. The sampling was conducted between 11:30 A.M. and 3:00 P.M. local time.
Volunteers used a coring tool to extract a single soil moisture sample of the 0-3 cm and 3-6 cm soil layers. Surface samples of the 0-1 cm soil were taken with a rectangular shaped scoop tool.
For volumetric soil moisture sampling, the primary measurement was the 0-6 cm dielectric constant at a single location in each site using impedance probes. The dielectric constant is converted to volumetric soil moisture using a calibration equation.
Computing Bulk Density and Soil Moisture
In the laboratory, samples were weighed, dried, and then weighed again. Gravimetric soil moisture (GSM) was computed as:
GSM = (wet weight - dry weight) / dry weight
The bulk density (BD) was determined by dividing the dry soil mass by the volume of the sample (3 cm cylinder of sample length). The bulk density for all 0-1 cm samples was assumed to be 1.5 g/cm3.
Volumetric soil moisture (VSM) was computed as:
VSM = GSM * BD
Note: For the 0-3 cm samples, the 3-6 cm bulk density was used due to the unreliability of the 0-3 cm samples.
Sensor or Instrument Description
Manual Soil Collection
Samples were collected manually in the field using coring tools, rectangular shaped scoop tools, and soil cans.
Infrared Thermometer (Pyrometer) and Temperature Probe
The surface temperature was sampled using handheld infrared thermometers, which are OMEGA OS643-LS Infrared Pyrometers. The instrument has an emissivity of 0.95, accuracy of ± 3%, and temperature range of 0 to 260°C (32 to 500°F). Refer to OMEGA Engineering for more information. Soil temperature was obtained using a temperature probe inserted to depths of 1 cm, 5 cm, and 10 cm. Several different temperature probes were used, but all have a metal rod, plastic top, and digital readout.
 |
 |
|
OS643-LS Infrared Pyrometer |
Temperature Probe |
Impedance Probes (ThetaProbes)
Investigators used impedance probes to measure surface volumetric soil moisture. The probes were Type ML2 ThetaProbe manually-operated impedance instruments manufactured by Delta-T Devices, Ltd. The ThetaProbes have four separate 6 cm stainless steel rods that were inserted vertically into the soil. Each instrument was connected to a handheld reader that delivers the electrical pulse, detects the return signal, and converts the period to voltage between 0 and about 1 V.
ML2 ThetaProbe
The software provided by the probe manufacturer calibrates the theta probes by calculating an estimate of volumetric soil moisture according to the following equation:
| Theta = | 1.07 + 6.4V - 6.4V2 + 4.7V3 - a0 |
a1 |
where a0 and a1 are 1.6 and 8.4, respectively. These estimates are provided in the data file.
Researchers also performed site-specific calibration for each field of sampling. Probe voltage readings from a row sampling point were compared to the volumetric soil moisture measured at the same point. A regression relationship was developed and new volumetric soil moisture values were estimated.
For several sites (GA01, GA08, GA09, GA24), recalibration of the probes was inappropriate because of the small dynamic range of the moisture values. For these sites, the general calibration coefficients were used for the site-specific calibration.
5. References and Related Publications
Please see the SMEX03 Web site for more information, and the NSIDC SMEX Web site to access data.
6. Document Information
Acronyms and Abbreviations
The following acronyms and abbreviations are used in this document.
| AMSR-E | Advanced Microwave Scanning Radiometer - Earth Observing System |
| ASCII | American Standard Code for Information Interchange |
| BD | Bulk Density |
| EDT | Eastern Daylight Time |
| FTP | File Transfer Protocol |
| GA | Georgia |
| GC | General Calibration |
| GSM | Gravimetric Soil Moisture |
| NASA | National Aeronautics and Space Administration |
| NSIDC | National Snow and Ice Data Center |
| SMEX | Soil Moisture Experiment |
| SMEX03 | Soil Moisture Experiment 2003 |
| SSC | Site-Specific Calibration |
| ST | Soil Temperature |
| TP | ThetaProbe |
| URL | Uniform Resource Locator |
| USDA-ARS | United States Department of Agriculture - Agricultural Research Service |
| VSM | Volumetric Soil Moisture |
| WGS84 | World Geodetic System 1984 |
Document Creation Date
March 2006
Document URL
http://nsidc.org/data/docs/daac/nsidc0288_smex03_reg_gsm_ga.gd.html
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