Soil Moisture Gravimetric Data (FIFE).
(Gravimetric Soil Moisture).
The Gravimetric Soil Moisture data set contains water content measurements obtained using gravimetric methods. This data set consists of information on the percentage of water in the samples on a dry-mass basis.
The aim of the FIFE soil moisture work was: (1) to characterize spatial and temporal patterns of soil moisture at the FIFE site, (2) to validate and calibrate remote sensing measurements of soil water, and (3) to evaluate alternative methods of measuring soil moisture both from the air and on the ground. A further goal was to develop techniques for comparing point and spatially continuous measurements of soil moisture. The FIFE soil moisture research was designed to advance the technology for characterizing soil moisture and contribute useful data to other FIFE investigations.
Soil moisture at different depths.
The gravimetrical soil moisture data were collected as baseline, site-monitoring information at many of the sites within the FIFE study area. These data were collected to characterize the spatial and temporal patterns of moisture content of the soils over this area during and between the FIFE Intensive Field Campaigns. Soil samples were routinely divided into 2 fractions (0-5 cm and 5-10 cm) and occasionally when soils were deep a third fraction (10-20 cm) was collected. A large number of sites were sampled during each of the three years of sample collection (1987-1989). In 1987, twenty locations (44 sites) were sampled throughout the FIFE study area. In 1988, 21 locations (22 sites), and in 1989, 13 locations (22 sites) were sampled. Multiple samples were collected from each of these locations and most samples were collected 30 meters from the center of the location. In 1987 and 1988 samples were collected only during IFC-5 (July-August). Samples were collected daily during the IFCs and about once per two weeks at other times.
SOIL_MOIST_GRAV_DATA.
Staff Science.
Soil Moisture Measurements for FIFE.
Contact 1:
Dr. Alan Nelson
USRA
Greenbelt, MD
(301)286-9783
nelson@pldsg3.gsfc.nasa.gov
Contact 2:
Galen Harbers
Univ. of Georgia
Griffin, GA
(404) 229-3296
gharber@griffin.uga.edu
The Gravimetric Soil Moisture data were collected for FIFE by the staff and students of the Evapotranspiration Laboratory at Kansas State University under the direction of Dr. Edward Kanemasu. The dedicated effort of A. Nelson and G. Harbers in the collection and preparation of these data is particularly appreciated.
Water content measurements by gravimetric methods involve weighing the wet sample, removing the water by drying in an oven, and reweighing the sample to determine the amount of water removed. Water content is obtained by dividing the difference between wet and dry masses by the mass of the dry sample to obtain the ratio of the mass of water to the mass of dry soil. When multiplied by 100, this becomes the percentage of water in the sample on a dry-mass (or, as often expressed, on a dry-weight) basis.
Apparatus required for gravimetric determination of water content include an auger or sampling tube to take a soil sample, soil containers with tight-fitting lids, an oven with means for controlling the temperature to 100 to 110 degrees Centigrade, a desiccator with active desiccant, and a balance for weighing the samples.
Ground.
Person on the ground.
Determination of soil moisture content.
Percent soil moisture.
The auger is manually inserted into the soil and a core removed.
Samples were usually obtained with a 4.86 cm diameter coring tube. In rocky or otherwise difficult-to-penetrate soils, a 2 cm diameter probe was used.
Auger:
Arts Manufacturing
105 Harrison and Oregon Trail
American Falls, ID 83211.
Auger specifications:
diameter 4.86 cm. length 5 cm
diameter 2.0 cm.
+/- 0.5% water content.
None.
None.
Gravimetric samples of the 0-5 cm and 5-10 cm of soil were taken using a double cylinder hammer driven core sampler. The total sample (approximately 100-150 grams) was put in a tin can and sealed with plastic electrical tape. Each sample can was identified by the sample site ID code. After collection, the samples in their cans were weighed to obtain the wet weight and then opened. Open cans were placed in ovens at 105 degrees Centigrade for a minimum of 48 hours for drying, then they were weighed again to obtain the dry weight. The weight of the can was then subtracted to determine the dry weight of the soil sample.
The sampling procedure for all stations except Station_ID=11 (sitegrid ID 4439) required the collection of 5 samples, one at the center of the site and one in each of the corners of the site (North, South, East and West) at a distance of 30 meters from the center. At Station 11, 10 samples were collected at distances of up to 100 meters from the center of the site (see the Field Notes Section for details).
Not available.
During IFC-1:
There were 44 stations. When two or three stations are collocated, (e.g., Stations 30 and 32 are represented by a single set of soil samples) the lower station number is included in this column.
Sample number according to the following codes which identify where and at what depth the samples were taken:
Sample Location:
NOTE: Hence, surface samples (i.e. 0-5 cm depth) are odd-numbered, subsurface samples (i.e. 5-10 cm depth) are even-numbered. Samples 3 through 10 are located approximately 30 m from the station.During IFC-4:
There were 44 stations.
Collocated stations are coded as follows:
Sample location in relation to the center of the site were represented according to the following codes: Locations 2 through 5 are located approximately 30 m from the station.The samples collected at Station 11 used a different sampling scheme. There were 10 sampling locations. To emphasize the different physical lay-out of this station, those locations are coded as follows:
The FIFE study area, with areal extent of 15 km by 15 km, is located south of the Tuttle Reservoir and Kansas River, and about 10 km from Manhattan, Kansas, USA. The northwest corner of the area has UTM coordinates of 4,334,000 Northing and 705,000 Easting in UTM Zone 14.
In 1987, soil samples were collected from 44 stations spread over the FIFE study area. Twenty-four of these stations were collocated so that 20 unique stations are reported in this data set for 1987. At each site, 5 or 10 soil cores were taken and samples divided into 2 and sometimes 3 depth fractions.
GRID_ID STN_ID NORTHING EASTING LATITUDE LONGITUDE COLLOCATED
-------- ------ -------- ------- --------- ---------- -------------
1246-SMK 40 4331666 714212 39 06 35 -96 31 21
1445-SMK 42 4331160 714090 39 06 19 -96 31 27
1478-SMK 38 4331216 720603 39 06 15 -96 26 56 79
1916-SMK 2 4330296 708270 39 05 56 -96 35 30 70,150,902
2043-SMK 44 4330003 713536 39 05 42 -96 31 51 35
2132-SMK 6 4329774 711336 39 05 36 -96 33 23 37,60
2516-SMK 14 4328956 708102 39 05 12 -96 35 38
2655-SMK 36 4328787 716070 39 05 00 -96 30 07 33,78,836,
936
2731-SMK 4 4328678 711110 39 05 01 -96 33 34 1,50,71,114,
402,403
2915-SMK 12 4328167 708028 39 04 47 -96 35 42
3129-SMK 8 4327702 710711 39 04 30 -96 33 51 -8
3414-SMK 10 4327286 707854 39 04 19 -96 35 51
3479-SMK 34 4327134 720890 39 04 02 -96 26 49 77
4268-SMK 30 4325626 718574 39 03 15 -96 28 27 25,32,51,76,
825,834,925,
932
4439-SMK 11 4325219 712795 39 03 07 -96 32 27 16,18,45,53,
73,106,811,
844,911,916,
945
4609-SMK 22 4324890 706705 39 03 02 -96 36 41 17,74
6340-SMK 20 4321484 713000 39 01 06 -96 32 23
6912-SMK 24 4320111 707336 39 00 26 -96 36 20 19,75,819,
919,924
6943-SMK 28 4320147 713500 39 00 22 -96 32 04 43,72
8739-SMK 26 4316699 712845 38 58 31 -96 32 35 21,821,921,
926,947,954
In 1988, soil samples were collected from 22 stations spread over the FIFE study area. Only one of these stations were located with other stations in 1988 so that 21 unique stations are reported in this data set for 1988. At each site, 5 or 10 soil cores were taken and samples divided into 2 and sometimes 3 depth fractions.
GRID_ID STN_ID NORTHING EASTING LATITUDE LONGITUDE COLLOCATED
-------- ------ --------- ------- -------- ---------- -------------
0847-SMK 829 4332344 714439 39 06 57 -96 31 11 29,52,151,
929
1246-SMK 840 4331625 714200 39 06 34 -96 31 22
1563-SMK 827 4331100 717610 39 06 14 -96 29 01
1816-SMK 802 4330410 708225 39 05 59 -96 35 32
1935-SMK 812 4330195 711927 39 05 49 -96 32 58
2123-SMK 805 4329866 709506 39 05 41 -96 34 39 5,905
2133-SMK 806 4329726 711604 39 05 34 -96 33 12 124,904,906,
931,937
2655-SMK 836 4328787 716070 39 05 00 -96 30 07 33,36,78,936
3021-SMK 807 4328000 709250 39 04 40 -96 34 52
3128-SMK 808 4327780 710683 39 04 32 -96 33 52
3317-SMK 810 4327463 708463 39 04 24 -96 35 25 910
3409-SMK 814 4327244 706850 39 04 18 -96 36 32
4139-SMK 831 4325850 712780 39 03 28 -96 32 27
4168-SMK 825 4325704 718646 39 03 18 -96 28 24 25,30,32,51,
76,834,
925,932
4439-SMK 811 4325219 712795 39 03 07 -96 32 27 11,16,18,45,
53,73,106,
844,911,916,
945
4509-SMK 817 4324960 706850 39 03 04 -96 36 35
6340-SMK 820 4321500 713000 39 01 07 -96 32 23
6469-SMK 823 4321189 718752 39 00 51 -96 28 25 23,923
6735-SMK 813 4320652 712073 39 00 40 -96 33 03 13,842,913
6912-SMK 819 4320178 707307 39 00 29 -96 36 21 19,24,75,
919,924
8639-SMK 821 4316771 712827 38 58 33 -96 32 36 21,26,921,
926,947,954
In 1989, soil samples were collected from 22 stations spread over the FIFE study area. Nine of these stations were located with other stations in 1989 so that 13 unique stations are reported in this data set for 1989. At each site, 5 or 10 soil cores were taken and samples divided into 2 and sometimes 3 depth fractions.
GRID_ID STN_ID NORTHING EASTING LATITUDE LONGITUDE COLLOCATED
-------- ------ -------- ------- -------- ---------- --------------
1478-SMK 938 4331223 720664 39 06 15 -96 26 53
1916-SMK 902 4330282 708259 39 05 55 -96 35 30 2,70,150
1942-SMK 944 4330133 713414 39 05 46 -96 31 56 946
2133-SMK 906 4329726 711604 39 05 34 -96 33 12 124,806,904,
931,937
2330-SMK 908 4329314 711066 39 05 22 -96 33 35
2655-SMK 936 4328787 716070 39 05 00 -96 30 07 33,36,78,836
3129-SMK 912 4327822 710820 39 04 33 -96 33 47
3317-SMK 910 4327395 708485 39 04 22 -96 35 24 810
4168-SMK 925 4325704 718646 39 03 18 -96 28 24 25,30,32,51,
76,825,834,
932
4439-SMK 916 4325193 712773 39 03 06 -96 32 28 11,16,18,45,
53,73,106,
811,844,911,
945
6735-SMK 913 4320652 712073 39 00 40 -96 33 03 13,813,842
6912-SMK 919 4320178 707307 39 00 29 -96 36 21 19,24,75,
819,924
8739-SMK 926 4316699 712845 38 58 31 -96 32 35 21,26,821,
921,947,954
In all years, the vertical coverage ranged from 0-20 cm below the surface of the prairie.
Not available.
These are point data.
Vertical resolution varied with depth. It was 5 cm from 0-10 of depth and 10 cm from 10-20 of depth.
Horizontal resolution was 30 meters for all sites except Station 11. For this site the horizontal resolution ranged from 60-150 m from the center of the site. The Field Notes Section gives a detailed listing of the sampling resolution at Station 11 (sitegrid ID = 4439).
Not available.
Not available.
Soil samples were collected in 1987, 1988 and 1989. The overall period of collection for 1987 was May 20 to November 4. In 1988, samples were collected between April 11 and September 28, and in 1989 samples were collected during IFC-5 (July 19 to August 12).
Not available.
The SQL definition for this table is found in the SM_GRAV.TDF file located on the CD-ROM Volume 1.
Parameter/Variable Name
Parameter/Variable Description Range Units Source
SITEGRID_ID This is a FIS grid location code. FIS Site grid codes (SSEE-III) give the south (SS) and east (EE) cell number in a 100 x 100 array of 200 m square cells. The last 3 characters (III) are an instrument identifier.
STATION_ID Site number for AMS or Flux min = 2, FIS station or transect point where max = 944 sample was taken.
OBS_DATE The date on which the sample was min = 20-MAY-87, KANSAS STATE taken. max = 12-AUG-89 UNIVERSITY
SAMPLE_LOCN Location of sample with respect min = 1, KANSAS STATE to site center (for IFC data). max = 20 UNIVERSITY 1 = center, 2 = north, 3 = west, 4 = south, 5 = east (approx 30 m in all cases). Station 11 is different - see documentation.
WET_WEIGHT_25MM The wet weight of the soil sample min = 6.49, [grams] WEIGHING taken at 25 mm. max = 190.9, BALANCE missing = -99.9
DRY_WEIGHT_25MM The dry weight of the soil sample min = 5.37, [grams] WEIGHING taken at 25 mm. max = 164, BALANCE missing = -99.9
SOIL_MOISTURE_25MM The soil moisture of the sample min = 3.3, [percent] KANSAS STATE taken at 25 mm. max = 81.8, UNIVERSITY missing = -99.9
WET_WEIGHT_75MM The wet weight of the soil sample min = 2.29, [grams] WEIGHING taken at 75 mm. max = 213.06, BALANCE missing = -99.9
DRY_WEIGHT_75MM The dry weight of the soil sample min = 1.77, [grams] WEIGHING taken at 75 mm. max = 167.01, BALANCE missing = -99.9
SOIL_MOISTURE_75MM The soil moisture of the sample min = 4.9, [percent] KANSAS STATE taken at 75 mm. max = 53.6, UNIVERSITY missing = -99.9
WET_WEIGHT_150MM The wet weight of the soil sample min = 31.2, [grams] WEIGHING taken at 150 mm. max = 92.6, BALANCE missing = -99.9
DRY_WEIGHT_150MM The dry weight of the soil sample min = 27.2, [grams] WEIGHING taken at 150 mm. max = 75.7, BALANCE missing = -99.9
SOIL_MOISTURE_150MM The soil moisture of the sample min = 12, [percent] KANSAS STATE taken at 150 mm. max = 32.9, UNIVERSITY missing = -99.9
FIFE_DATA_CRTFCN_CODE * The FIFE Certification Code for min = D, FIS the data, in the following format: max = D CPI (Certified by PI), CPI-??? (CPI - questionable data).
LAST_REVISION_DATE The last revision date for the min = 13-AUG-87, FIS data, in the format (DD-MMM-YY). max = 18-OCT-89
Footnote:
* Valid levels
The primary certification codes are:
The certification code modifiers are:
SITEGRID_ID STATION_ID OBS_DATE SAMPLE_LOCN WET_WEIGHT_25MM
----------- ---------- --------- ----------- ---------------
1916-SMK 2 20-MAY-87 1 13.63
1916-SMK 2 20-MAY-87 2 15.02
1916-SMK 2 20-MAY-87 3 12.14
1916-SMK 2 20-MAY-87 4 8.81
1916-SMK 2 20-MAY-87 5 14.16
2731-SMK 4 20-MAY-87 1 16.39
2731-SMK 4 20-MAY-87 2 16.89
2731-SMK 4 20-MAY-87 3 14.15
2731-SMK 4 20-MAY-87 4 16.81
2731-SMK 4 20-MAY-87 5 -99.9
2132-SMK 6 20-MAY-87 1 16.84
2132-SMK 6 20-MAY-87 2 18.73
DRY_WEIGHT_25MM SOIL_MOISTURE_25MM WET_WEIGHT_75MM DRY_WEIGHT_75MM
--------------- ------------------ --------------- ---------------
11.43 19.2 17.64 15.22
12.29 22.2 18.88 16.18
10.06 20.7 17.6 15.71
7.09 24.3 19.44 16.83
11.6 22.1 18.35 15.34
14 17.1 17.81 15.51
14.44 17 17.03 14.82
12.29 15.1 16.05 14.04
14.07 19.5 16.77 14.02
-99.9 -99.9 -99.9 -99.9
12.29 37 26.96 20.86
14.52 29 22.12 17.03
SOIL_MOISTURE_75MM WET_WEIGHT_150MM DRY_WEIGHT_150MM SOIL_MOISTURE_150MM
------------------ ---------------- ---------------- -------------------
15.9
16.7
12
15.5
19.6
14.8
14.9
14.3
19.6
-99.9
29.2
29.9
FIFE_DATA_CRTFCN_CODE LAST_REVISION_DATE
--------------------- ------------------
CPI 31-AUG-87
CPI 31-AUG-87
CPI 31-AUG-87
CPI 31-AUG-87
CPI 31-AUG-87
CPI 31-AUG-87
CPI 31-AUG-87
CPI 31-AUG-87
CPI 31-AUG-87
CPI 31-AUG-87
CPI 31-AUG-87
CPI 31-AUG-87
A general description of data granularity as it applies to the IMS appears in the EOSDIS Glossary.
The CD-ROM file format consists of numerical and character fields of varying length separated by commas. The character fields are enclosed with a single apostrophe. There are no spaces between the fields. Each file begin with five header records. Header records contain the following information:
Each field represents one of the attributes listed in the chart in the Data Characteristics Section and described in detail in the TDF file. These fields are in the same order as in the chart.
Percent soil moisture on a weight basis.
Calculated according to the following formula:
weight of wet soil
Percent Water content = [ ------------------ - 1 ] x 100.
weight of dry soil
Not Applicable.
None.
None.
Percent water content.
None.
Errors could arise in water content measurements depending on the technique used to avoid absorption of water from the air during cooling and prior to weighing. Also, the time necessary to reach 'constant' weight will depend upon the type of oven used (forced-draft of convection type), the size or depth of the sample, the nature of the soil, and if the oven is loaded heavily or not. Water content values for stony or gravely soils, both on a mass and volume basis, can be grossly misleading. The problem arises from the fact that a large rock can occupy appreciable volume in a soil sample and contribute appreciably to the mass without making a commensurate contribution to the porosity or water capacity of the soil.
Not available.
The crews collecting these data were generally conscientious. Adequate drying-oven space was available, therefore, dry weight should be representative of a "constant" dry weight. These data should be as accurate as gravimetric sampling would allow.
In 1989, the variation of gravimetric soil moisture values from day-to-day during the field campaign were plotted to check for anomalous data points.
No quantitative assessment was made, see the Confidence Level/Accuracy Judgment Section.
Other errors mentioned in the Sources of Error Section above were not quantified.
Not available.
The data verification performed by the ORNL DAAC deals with the quality of the data format, media, and readability. The ORNL DAAC does not make an assessment of the quality of the data itself except during the course of performing other QA procedures as described below.
The FIFE data were transferred to the ORNL DAAC via CD-ROM. These CD-ROMs are distributed by the ORNL DAAC unmodified as a set or in individual volumes, as requested. In addition, the DAAC has incorporated each of the 98 FIFE tabular datasets from the CD-ROMs into its online data holdings. Incorporation of these data involved the following steps:
Each distinct type of data (i.e. "data set" on the CD-ROM), is accompanied by a documentation file (i.e., .doc file) and a data format/structure definition file (i.e., .tdf file). The data format files on the CD-ROM are Oracle SQL commands (e.g., "create table") that can be used to set up a relational database table structure. This file provides column/variable names, character/numeric type, length, and format, and labels/comments. These SQL commands were converted to SAS code and were used to create SAS data sets and subsequently to input data files directly from the CD-ROM into a SAS dataset. During this process, file names and directory paths were captured and metadata was extracted to the extent possible electronically. No files were found to be corrupted or unreadable during the conversion process.
Additional Quality Assurance procedures were performed as follows:
As errors are discovered in the online tabular data by investigators, users, or DAAC staff, corrections are made in cooperation with the principal investigators. These corrections are then distributed to users. CD-ROM data are corrected when re-mastering occurs for replenishment of CD-ROM stock.
Not available.
Not available.
This data set can be used in conjunction with other soil moisture data to validate the soil moisture values predicted by the airborne remote sensing instruments during FIFE. It can be used with caution in similar prairie landscapes to compare remote sensing derived soil moisture and field measured soil moisture.
Not available.
These data were collected to characterize the spatial and temporal patterns of moisture content of the soils over this area during and between the FIFE Intensive Field Campaigns.
The FIFE field campaigns were held in 1987 and 1989 and there are no plans for new data collection. Field work continues near the FIFE site at the Long-Term Ecological Research (LTER) Network Konza research site (i.e., LTER continues to monitor the site). The FIFE investigators are continuing to analyze and model the data from the field campaigns to produce new data products.
Software to access the data set is available on the all volumes of the FIFE CD-ROM set. For a detailed description of the available software see the Software Description Document.
ORNL DAAC User Services Office
Oak Ridge National Laboratory
Telephone: (865) 241-3952
FAX: (865) 574-4665
Email: ornldaac@ornl.gov
ORNL Distributed Active Archive Center
Oak Ridge National Laboratory
USA
Telephone: (865) 241-3952
FAX: (865) 574-4665
Email: ornldaac@ornl.gov
Users may place requests by telephone, electronic mail, or FAX. Data is also available via the World Wide Web at http://daac.ornl.gov.
FIFE data are available from the ORNL DAAC. Please contact the ORNL DAAC User Services Office for the most current information about these data.
Gravimetric Soil Moisture data are available on FIFE CD-ROM Volume 1. The CD-ROM file names are as follows: \DATA\SOILMSTR\SM_GRAV\GRIDxxxx\YyyMmm\ydddgrid.SMG or \DATA\SOILMSTR\SM_GRAV\GRIDxxxx\Yyy\ydddgrid.SMG.
Where xxxx is the four digit code for the location within the FIFE site grid, yy is the last two digits of the year (e.g., Y87 = 1987), mm is the month of the year (e.g., M12 = December), and ddd is the day of the year, (e.g., 061 = sixty-first day in the year). Note: capital letters indicate fixed values that appear on the CD-ROM exactly as shown here, lower case indicates characters (values) that change for each path and file.
The format used for the filenames is: ydddgrid.sfx, where grid is the four-number code for the location within the FIFE site grid, y is the last digit of the year (e.g., 7 = 1987, and 9 = 1989), and ddd is the day of the year. The filename extension (.sfx), identifies the data set content for the file (see the Data Characteristics Section) and is equal to .SMG for this data set.
Gardner, W.H. 1986. Water content. p.635-662. In: A. Klute (ed.) Methods of Soil Analysis. Part 1. Physical and mineralogical methods, 2nd ed. Agronomy Monogr. 9. ASA and SSSA. Madison, WI.
Engman, E.T., W. Kustas, T.J. Schmugge, and J.R. Wang. 1987. Relationship among the remotely sensed soil moisture, streamflow, and evapotranspiration. AGU Fall Meeting. San Francisco.
Engman, E.T., G. Angus, and W. Kustas. 1989. Relationships between the hydrologic balance of a small watershed and remotely sensed soil moisture. Remote Sensing and Large Scale Processes. IAHS Publ. No. 186. Proc. IAHS. 3rd Int. Asso. Baltimore, MD.
Schmugge,T.J. 1978. Remote sensing of surface soil moisture. J. Appl. Meteorol. 17:1547-1557.
Schmugge, T.J., T.J. Jackson, and H.L. McKim. 1980. Survey of methods of soil moisture determination. Water Resources Res. 16(16):961-979.
Wetzel, P.J., and J.T. Chang. 1987. Concerning the relationship between evapotranspiration and soil moisture. J. Clim. Appl. Meteor.
The Collected Data of the First ISLSCP Field Experiment is archived at the EOS Distributed Active Archive Center (DAAC) at Oak Ridge National Laboratory (ORNL), Oak Ridge, Tennessee (see Data Center Identification). Documentation about using the archive and/or online access to the data at the ORNL DAAC is not available at this revision.
A general glossary for the DAAC is located at Glossary.
A general list of acronyms for the DAAC is available at Acronyms.
April 28, 1994 (citation revised on October 15, 2002).
This document has been reviewed by the FIFE Information Scientist to eliminate technical and editorial inaccuracies. Previous versions of this document have been reviewed by the Principal Investigator, the person who transmitted the data to FIS, a FIS staff member, or a FIFE scientist generally familiar with the data. It is believed that the document accurately describes the data as collected and archived on FIFE CD-ROM series.
February 18, 1996.
ORNL-FIFE_SM_GRAV.
Nelson, A., and G. Harbers. 1994. Soil Moisture Gravimetric Data (FIFE). Data set. Available on-line [http://www.daac.ornl.gov] from Oak Ridge National Laboratory Distributed Active Archive Center, Oak Ridge, Tennessee, U.S.A. Also published in D. E. Strebel, D. R. Landis, K. F. Huemmrich, and B. W. Meeson (eds.), Collected Data of the First ISLSCP Field Experiment, Vol. 1: Surface Observations and Non-Image Data Sets. CD-ROM. National Aeronautics and Space Administration, Goddard Space Flight Center, Greenbelt, Maryland, U.S.A. (available from http://www.daac.ornl.gov).
http://daac.ornl.gov/FIFE/Datasets/Soil_Moisture/Soil_Moisture_Gravimetric_Data.html