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SOIL MOISTURE NEUTRON PROBE DATA (FIFE)
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Soil Moisture Neutron Probe Data (FIFE)

Summary:

The neutron-probe data present a series of measurements of volumetric water content in the soil profile compiled using the neutron method. These data were collected from throughout the FIFE study area from May 1987 through August 1989.

The neutron method of measuring soil water content uses the principle of neutron thermalization. When both hydrogen and oxygen are considered, water has a marked effect on slowing or thermalizing neutrons. Thermal neutron density is easily measured with a detector, if the capture cross-section remains constant then the thermal neutron density may be calibrated against water concentration on a volume basis.

Table of Contents:

  1. Data Set Overview
  2. Investigator(s)
  3. Theory of Measurements
  4. Equipment
  5. Data Acquisition Methods
  6. Observations
  7. Data Description
  8. Data Organization
  9. Data Manipulations
  10. Errors
  11. Notes
  12. Application of the Data Set
  13. Future Modifications and Plans
  14. Software
  15. Data Access
  16. Output Products and Availability
  17. References
  18. Glossary of Terms
  19. List of Acronyms
  20. Document Information

1. Data Set Overview:

Data Set Identification:

Soil Moisture Neutron Probe Data (FIFE).
(Neutron Probe Soil Moisture).

Data Set Introduction:

The neutron-probe data present a series of measurements of volumetric water content in the soil profile. These data were collected throughout the FIFE study area from May 1987 through August 1989.

Objective/Purpose:

The focus of this data collection was to measure profiles of soil-moisture content at intervals of 20 cm to a depth of 2 meters or to the level of impenetrable rock layers, whichever was shallower.

Summary of Parameters:

Soil moisture at several depths.

Discussion:

The neutron-probe data present a series of measurements of volumetric water content (volume of water in the sample/volume of total sample) in the soil profile. These measurements are not directly comparable with the gravimetric water content measured at the soil surface (weight of water in the sample/weight of dried sample). Because the sphere of influence of the neutron-probe instrument would extend into the air above the soil surface, measurements in the top 20 cm of the soil were determined gravimetrically and converted to volumetric values using measurements of bulk density. These data were collected throughout the FIFE study area from May 1987 through August 1989. During this time range measurements were made only during the growing seasons of 1987 and 1988 and during late summer (July and August) of 1989.

Related Data Sets:

FIS Data Base Table Name:

SOIL_MOIST_NEUTRON_DATA.

2. Investigator(s):

Investigator(s) Name and Title:

Dr. Edward T. Kanemasu, Leader
Evapotranspiration Lab.
Kansas State University

Title of Investigation:

Soil Moisture Measurements for FIFE.

Contact Information:

Contact 1:
Dr. Alan Nelson
NASA Goddard Space Flight Center
Greenbelt, MD
(301) 286-9783
nelson@pldsg3.gsfc.nasa.gov

Contact 2:
Dr. Tanvir Shah
Alabama A&M University
Normal, AL
(205) 851-5462
aamth01@asnaam.asn.net

Contact 3:
Galen Harbers
University of Georgia
Griffin, GA
(404) 229-3296
gharber@griffin.uga.edu

Requested Form of Acknowledgment.

The Neutron Probe 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, T. Shah and G. Harbers in the collection and preparation of these data is particularly appreciated.

3. Theory of Measurements:

The neutron method of measuring soil water content uses the principle of neutron thermalization. Hydrogen nuclei have a marked property for scattering and slowing neutrons. High-energy neutrons (5.05 [MeV]) emitted from a radioactive substance such as radium-beryllium or americium-beryllium slow down and change direction by elastic collisions with atomic nuclei (thermalization). The energy of the neutrons are reduced to about the thermal energy of atoms in a substance at room temperature. Considering both energy transfer and scattering cross-section, it is evident that hydrogen, having a nucleus of about the same size and mass as the neutron, has a much greater thermalizing effect on fast neutrons than any other element. When both hydrogen and oxygen are considered, water has a marked effect on slowing or thermalizing neutrons. Thermal neutron density is easily measured with a detector, if the capture cross-section, except for that due to water, remains constant (i.e., chemical composition constant), then the thermal neutron density may be calibrated against water concentration on a volume basis.

4. Equipment:

Sensor/Instrument Description:

The neutron moisture depth probe and meter consisted of 4 items:

  1. Fast neutrons (usually americium-241/beryllium),
  2. A detector of thermalized neutrons,
  3. A protective shield composed of lead (for gamma ray absorption), and
  4. Paraffin (for neutron absorption).

The paraffin also served as a reference standard. The neutron source was a small capsule located on the side of the detector cylinder.

A soil auger was used to create the opening for the thin-walled aluminum access tubing. The diameter of the auger was slightly smaller than the tubing to assure a tight fit.

Collection Environment:

Ground.

Source/Platform:

Ground.

Source/Platform Mission Objectives:

Determination of volumetric soil moisture content.

Key Variables:

Soil moisture by volume at 14 depths.

Principles of Operation:

Thermalization of neutrons by water.

Sensor/Instrument Measurement Geometry:

The zone of influence for 5-MeV neutrons is roughly spherical with a radius of about 15 cm in wet soil and 70 cm in dry soil.

Manufacturer of Sensor/Instrument:

CPN Corporation
2830 Howe Road
Martinez, California 94553.

Calibration:

In 1988, the two neutron probes used during FIFE were calibrated at site 802 (SITGRID_ID 1816) and at one other site within the Konza Prairie Natural Research Area in the northwest quadrant of the FIFE study area. Neutron counts under saturated and very dry, soil moisture conditions were taken. Immediately after taking the neutron counts, soil samples were collected to obtain the soil moisture contents.

Specifications:

50 milli-Rem per hour source of Americium/Beryllium

Tolerance:

Approximately +/- 0.005 [g][cm^-3].

Frequency of Calibration:

Once.

Other Calibration Information:

None.

5. Data Acquisition Methods:

The soil auger is used to form the hole for installation of the access tubing. The access tubing usually is left so as to protrude about 10 cm above the soil surface and is covered with an empty can or stopper between readings to keep water and debris out.

A measurement is made by placing the probe unit over the access tube preparatory to lowering it into the hole. An appropriate counting time (15 seconds during FIFE measurements) is shield. Then one or more counts are made at each selected depth. The calibration curve is used to convert the count ratios (count in soil/count into volumetric water content, or to read water content directly if the equipment has the required built-in computer.

6. Observations:

Data Notes:

Not available.

Field Notes:

There were 55 stations. Collocated stations are coded using the lowest station number. Those stations are:

Sample location in relation to the center of the site were represented according to the following codes during 1988: 1: Central part of station location.
2: North of station location.
3: West of station location.
4: South of station location.
5: East of station location.
Locations 2 through 5 are located approximately 30 m from the station.

During 1989 the 5 neutron probe access tubes were installed with the AB (Wind Aligned Blobs - see FIFE experiment plan for 1989) sector Shashi's site (stations 11, 16 and 18) was laid out differently, 8 neutron tubes (plus two additional locations which were sampled for daily soil moisture measurements within 10 cm of the surface). To emphasize the different physical layout of this station, those locations are coded as follows:

11: 150 m from center, approximately 10 degrees North of due East
12: 100 m from center, approximately 10 degrees North of due East
13: 150 m from center, approximately 10 degrees North of Southeast
14: 100 m from center, approximately 10 degrees North of Southeast
15: 150 m from center, approximately 10 degrees East of due South
16: 100 m from center, approximately 10 degrees East of due South
17: 150 m from center, approximately 10 degrees West of due South
18: 100 m from center, approximately 10 degrees West of due South
19: 100 m from center, approximately Southwest
20: 60 m from center, approximately Southwest
Volumetric soil moisture measurements were made at the following depths:
    Column:   Depth:
(cm)
4 . . . 200     (Neutron probe measurement)
5 . . . 180     (Neutron probe measurement)
6 . . . 160     (Neutron probe measurement)
7 . . . 140     (Neutron probe measurement)
8 . . . 120     (Neutron probe measurement)
9 . . . 100     (Neutron probe measurement)
10 . . .  80     (Neutron probe measurement)
11 . . .  60     (Neutron probe measurement)
12 . . .  50     (Neutron probe measurement)
13 . . .  40     (Neutron probe measurement)
14 . . .  30     (Neutron probe measurement)
15 . . .  20     (Neutron probe measurement)
16 . . . 5-10    (Gravimetric sample converted to volumetric data)
17 . . . 0-5     (Gravimetric sample converted to volumetric data)
Dry gravimetric samples weighing more than 65 grams were assumed to have been collected with the volumetric sampler and volumetric water content was calculated via the following equation: (Wet weight - Dry weight)/volume Smaller samples were converted to a volumetric basis via the following equation: (Percent by weight) X (bulk density) With the following exceptions, the surface gravimetric samples were collected on the same day as the neutron readings during 1987:
            Station   Neutron          Gravimetric
-------   -------          -----------
17      June 16           June 15
19      June 16           June 15
20      June 16           June 15
21      June 16           June 15
28      June 16           June 15
36      June 16           June 15
38      June 16           June 15
17      July 22           July 20
19      July 22           July 20
20      July 21           July 20
21      July 22           July 20
28      July 22           July 20
36      July 21           July 20
38      July 21           July 20
44      July 22           July 20
17      August 1          July 30
19      August 1          July 30
20      July 31           July 30
21      August 1          July 30
28      August 1          July 30
36      July 31           July 30
38      July 31           July 30
44      August 1          July 30
2      August  7         August  8
4      August  7         August  8
10      August  7         August  8
11      August  5         August  8
17      August  7         August  8
19      August  7         August  8
20      August  5         August  6
21      August  7         August  8
28      August  7         August  8
36      August  5         August  6
38      August  5         August  7
2      August 14         August 13
4      August 14         August 13
21      August 13         August 11
2      August 23         August 21
4      August 23         August 21
9      August 20         August 21
10      August 23         August 21
19      August 22         August 21
21      August 22         August 21
28      August 22         August 21
44      August 19         August 20
9      September  5      September  2
13      September  4      September  2
15      September  4      September  2
17      September  4      September  3
19      September  5      September  3
20      September  4      September  3
21      September  4      September  3
23      September  4      September  2
28      September  5      September  3
29      September  4      September  2
36      September  2      September  3
38      September  2      September  3
44      September  4      September  3
1      September 16      September 19
2      September 16      September 15
3      September 16      September 19
4      September 16      September 15
5      September 16      September 19
9      September 14      September 19
10      September 16      September 15
13      September 14      September 19
15      September 14      September 19
17      September 14      September 15
19      September 14      September 15
20      September 14      September 15
21      September 14      September 15
23      September 14      September 19
28      September 14      September 15
29      September 14      September 19
36      September 17      September 15
44      September 14      September 15
17      September 26      September 24
19      September 26      September 24
20      September 26      September 24
21      September 26      September 24
28      September 26      September 24
36      September 25      September 24
44      September 25      September 24
2      October    4      October    5
4      October    4      October    5
10      October    4      October    5
20      October    3      October    5
36      October    3      October    5
44      October    6      October    5
2      October   18      October   15
4      October   18      October   15
10      October   18      October   14
17      October   19      October   14
19      October   19      October   14
20      October   19      October   15
21      October   19      October   15
28      October   19      October   15
36      October   17      October   15
44      October   19      October   15

7. Data Description:

Spatial Characteristics:

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.

Spatial Coverage:

Coverage for vertical measurements ranged from 2.5 cm to 200 cm with measurements made at 14 discrete depths (200, 180, 160, 140, 120, 100, 80, 60, 50, 40, 30, 20, 7.5, and 2.5 cm).

In the horizontal dimension soil samples were collected from 37 Sitegrids spread over the FIFE study area. Not all sitegrids were sampled in all three years.

       SITEGRID  NORTHING  EASTING  LATITUDE   LONGITUDE   ELEV  SLOPE  ASPECT
--------  --------  -------- ---------- ----------- ----  -----  ------
0847-NPK  4332344   714439   39 06 57  -96 31 11    418    1     TOP
1246-NPK  4331625   714200   39 06 34  -96 31 22    410   12     S
1445-NPK  4331160   714090   39 06 19  -96 31 27    400            
1478-NPK  4331223   720664   39 06 15  -96 26 53    375    2     N
1563-NPK  4331100   717610   39 06 14  -96 29 01    366   18     W
1816-NPK  4330410   708225   39 05 59  -96 35 32    345    2     N
1916-NPK  4330282   708259   39 05 55  -96 35 30    351    2     N
1942-NPK  4330121   713402   39 05 46  -96 31 57    420    1     TOP
2043-NPK  4330003   713536   39 05 42  -96 31 51    415
2123-NPK  4329866   709506   39 05 41  -96 34 39    405    1     TOP
2132-NPK  4329774   711336   39 05 36  -96 33 23    405
2133-NPK  4329726   711604   39 05 34  -96 33 12    443    1     TOP
2139-NPK  4329843   712789   39 05 37  -96 32 23    385
2330-NPK  4329314   711066   39 05 22  -96 33 35    424    5     E
2428-NPK  4329265   710635   39 05 20  -96 33 53    415
2516-NPK  4328956   708102   39 05 12  -96 35 38    405
2655-NPK  4328787   716070   39 05 00  -96 30 07    367    4     E
2731-NPK  4328678   711110   39 05 01  -96 33 34    446
2915-NPK  4328167   708028   39 04 47  -96 35 42    415
3129-NPK  4327822   710820   39 04 33  -96 33 47    431   14     E
3221-NPK  4327682   709112   39 04 30  -96 34 58    410
3317-NPK  4327463   708463   39 04 24  -96 35 25    420   13     W
3414-NPK  4327286   707854   39 04 19  -96 35 51    410
3479-NPK  4327134   720890   39 04 02  -96 26 49    420
3921-NPK  4326116   709185   39 03 39  -96 34 57    415
4168-NPK  4325704   718646   39 03 18  -96 28 24    438    1     TOP
4439-NPK  4325219   712795   39 03 07  -96 32 27    445    2     N
4509-NPK  4324960   706850   39 03 04  -96 36 35    390    3     SE
4609-NPK  4324766   706700   39 02 58  -96 36 41    398
5926-NPK  4322227   710270   39 01 32  -96 34 16    370 
6340-NPK  4321500   713000   39 01 07  -96 32 23    410    4     SW
6469-NPK  4321189   718752   39 00 51  -96 28 25    440    3     NE
6735-NPK  4320652   712073   39 00 40  -96 33 03    385    1     BOTTOM
6912-NPK  4320178   707307   39 00 29  -96 36 21    385    2     N
6943-NPK  4320147   713500   39 00 22  -96 32 04    415
8639-NPK  4316771   712827   38 58 33  -96 32 36    440    1     TOP
8739-NPK  4316699   712845   38 58 31  -96 32 35    442    1     TOP

Spatial Coverage Map:

Not available.

Spatial Resolution:

These are point data.

Vertical resolution varied with depth. It ranged from 1.25 cm at in the top layer to 10 cm in the deepest layer (180-200 cm).

Horizontal resolution was 30 meters for all sites except Station 11 (sitegrid = 4439-NPK). 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).

Projection:

Not available.

Grid Description:

Not available.

Temporal Characteristics:

Temporal Coverage:

The overall time period for collection of these data was from May 28, 1987 through August 10, 1989. Soil samples were collected from late spring through the fall of 1987 (May 28 - November 6) and 1988 (April 11-September 29), and during late summer of 1989 (July 24-August 10). During these periods there were 58, 71 and 9 days of data, respectively.

Temporal Coverage Map:

Not available.

Temporal Resolution:

There were 136 days of data. During the Intensive Field Campaigns the data were collected weekly, at other times the measurement interval was 10 days to 2 weeks.

Data Characteristics:

The SQL definition for this table is found in the SM_NEUT.TDF file located on FIFE 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 = 1, FIS station or transect point where max = 944 sample was taken.
OBS_DATE The date on which the sample was min = 28-MAY-87, KANSAS STATE taken. max = 10-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 30m in all cases). Station 11 is different - see documentation.
SOIL_MOISTURE_200CM Measurement of soil moisture at min = 27.1, [percent] NEUTRON 200 cm. max = 40.4, PROBE missing = -9.9
SOIL_MOISTURE_180CM Measurement of soil moisture at min = 25.4, [percent] NEUTRON 180 cm. max = 40.4, PROBE missing = -9.9
SOIL_MOISTURE_160CM Measurement of soil moisture at min = 24.2, [percent] NEUTRON 160 cm. max = 40.7, PROBE missing = -9.9
SOIL_MOISTURE_140CM Measurement of soil moisture at min = 20.2, [percent] NEUTRON 140 cm. max = 40.4, PROBE missing = -9.9
SOIL_MOISTURE_120CM Measurement of soil moisture at min = 19.8, [percent] NEUTRON 120 cm. max = 43.3, PROBE missing = -9.9
SOIL_MOISTURE_100CM Measurement of soil moisture at min = 20.3, [percent] NEUTRON 100 cm. max = 41.7, PROBE missing = -9.9
SOIL_MOISTURE_80CM Measurement of soil moisture at min = 15.9, [percent] NEUTRON 80 cm. max = 41, PROBE missing = -9.9
SOIL_MOISTURE_60CM Measurement of soil moisture at min = 15.7, [percent] NEUTRON 60 cm. max = 43.3, PROBE missing = -9.9
SOIL_MOISTURE_50CM Measurement of soil moisture at min = 17.4, [percent] NEUTRON 50 cm. max = 45.1, PROBE missing = -9.9
SOIL_MOISTURE_40CM Measurement of soil moisture at min = 13.3, [percent] NEUTRON 40 cm. max = 46.7, PROBE missing = -9.9
SOIL_MOISTURE_30CM Measurement of soil moisture at min = 11, [percent] NEUTRON 30 cm. max = 48.8, PROBE missing = -9.9
SOIL_MOISTURE_20CM Measurement of soil moisture at min = 2, [percent] NEUTRON 20 cm. max = 47.2, PROBE missing = -9.9
SOIL_MOISTURE_75MM Measurement of soil moisture at min = 5.7, [percent] NEUTRON 75 mm. max = 63.3, PROBE missing = -9.9
SOIL_MOISTURE_25MM Measurement of soil moisture at min = 4.9, [percent] NEUTRON 25 mm. max = 70.4, PROBE missing = -9.9
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 data, in the format (DD-MMM-YY). max = 10-AUG-89
Footnote:

* Valid levels

The primary certification codes are: EXM Example or Test data (not for release) PRE Preliminary (unchecked, use at your own risk) CPI Checked by Principal Investigator (reviewed for quality) CGR Checked by a group and reconciled (data comparisons and cross checks)

The certification code modifiers are: PRE-NFP Preliminary - Not for publication, at the request of investigator. CPI-MRG PAMS data which is "merged" from two separate receiving stations to eliminate transmission errors. CPI-??? Investigator thinks data item may be questionable.

Sample Data Record:

     SITEGRID_ID  STATION_ID  OBS_DATE   SAMPLE_LOCN  SOIL_MOISTURE_200CM
-----------  ----------  ---------  -----------  -------------------
2731-NPK         1       29-MAY-87       1              -9.90
2731-NPK         1       29-MAY-87       2              35.30
2731-NPK         1       29-MAY-87       3              36.90
2731-NPK         1       29-MAY-87       4              -9.90
     SOIL_MOISTURE_180CM    SOIL_MOISTURE_160CM    SOIL_MOISTURE_140CM
-------------------    -------------------    -------------------
9.90                 -9.90                 33.50
34.20                 34.40                 34.60
34.90                 35.40                 36.10
9.90                 -9.90                 -9.90
     SOIL_MOISTURE_120CM    SOIL_MOISTURE_100CM    SOIL_MOISTURE_80CM
-------------------    -------------------    ------------------
33.90                 34.50                 35.20
34.70                 36.20                 37.20
35.70                 36.40                 38.10
31.90                 32.00                 32.70
    SOIL_MOISTURE_60CM      SOIL_MOISTURE_50CM     SOIL_MOISTURE_40CM
------------------     ------------------     ------------------
37.90                 38.80                 40.50
39.80                 38.50                 36.70
39.60                 37.50                 36.50
38.80                 40.00                 41.20
    SOIL_MOISTURE_30CM      SOIL_MOISTURE_20CM     SOIL_MOISTURE_75MM
------------------     ------------------     ------------------
41.00                 35.30                 39.40
37.10                 34.40                 41.20
36.90                 33.60                 42.50
40.80                 30.30                 42.00
    SOIL_MOISTURE_25MM      FIFE_DATA_CRTFCN_CODE   LAST_REVISION_DATE
------------------     ---------------------   ------------------
44.70                 CPI                   15-DEC-87
41.20                 CPI                   15-DEC-87
40.80                 CPI                   15-DEC-87
46.00                 CPI                   15-DEC-87 

8. Data Organization:

Data Granularity:

There were 136 days of point data. Coverage for vertical measurements ranged from 2.5 cm to 200 cm with measurements made at 14 discrete depths. Vertical resolution varied with depth. It ranged from 1.25 cm at in the top layer to 10 cm in the deepest layer (180-200 cm).

Horizontal resolution was 30 meters for all sites except Station 11 (sitegrid = 4439-NPK). For this site the horizontal resolution ranged from 60-150 m from the center of the site.

A general description of data granularity as it applies to the IMS appears in the EOSDIS Glossary.

Data Format:

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 begins with five header records. Header records contain the following information: Record 1 Name of this file, its table name, number of records in this file, path and name of the document that describes the data in this file, and name of principal investigator for these data. Record 2 Path and filename of the previous data set, and path and filename of the next data set. (Path and filenames for files that contain another set of data taken at the same site on the same day.) Record 3 Path and filename of the previous site, and path and filename of the next site. (Path and filenames for files of the same data set taken on the same day for the previous and next sites (sequentially numbered by SITEGRID_ID)). Record 4 Path and filename of the previous date, and path and filename of the next date. (Path and filenames for files of the same data set taken at the same site for the previous and next date.) Record 5 Column names for the data within the file, delimited by commas. Record 6 Data records begin.

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.

9. Data Manipulations:

Formulae:

Derivation Techniques and Algorithms:

An empirical equation for water content in terms of the count ratio, used over the range of water contents of usual interest, is as follows:

THETA = a + bf. where: f is the count rate ratio, I/I(std),
a and b are parameters which depend upon soil characteristics and the standard count when the neutron source and detector are in the shield.

R = 100 cm / (1.4 + 10 m)

where: R = radius of the sphere of influence accounting for 95% of the neutron flux which would be obtained in an infinite medium (Olgaard, 1965).
m = water content in [g][cm^-3].
Volumetric water content was calculated via the following equation: (Wet weight - Dry weight)/volume.

Data Processing Sequence:

Raw counts were logged in the field, further processing of the data, to obtain the soil volumetric moisture contents, was carried out on a personal computer in the lab.

Processing Steps:

Not available.

Processing Changes:

None.

Calculations:

For the near-surface measurements (SOIL_MOISTURE_75MM and SOIL_MOISTURE_25MM) dry gravimetric samples weighing more than 65 grams were assumed to have been collected with the volumetric sampler and volumetric water content was calculated via:

(Wet weight - Dry weight) / volume Smaller samples were converted to a volumetric basis via: (Percent by weight) X (bulk density)

Special Corrections/Adjustments:

In the 1988 and 1989 data -9.9 indicates missing values.

Calculated Variables:

Not available.

Graphs and Plots:

None.

10. Errors:

Sources of Error:

Errors could arise from spatial variation in water content which depend on spatial variation in soil constituents, profile structure and the degree to which calibration conditions resemble particular field conditions. Such variations can involve bias as well as unidentified error associated with site variation.

When sharp interfaces or wetting-fronts exist, the shape or size of the volume of influence may be altered as the water content changes. Such changes would lead to a volume of influence that is not centered on the neutron sensor. An additional factor involves perturbations in the water content caused by temperature changes in the soil surrounding a neutron-probe access-tube induced by heat conduction along the tube. Some errors in water content measurement may also occur with random neutron emission.

Quality Assessment:

Data Validation by Source:

Not available.

Confidence Level/Accuracy Judgment:

Proper techniques using a neutron probe were followed and these data should be as good as possible using this technique.

Measurement Error for Parameters:

Not available.

Additional Quality Assessments:

FIS staff applied a general Quality Assessment (QA) procedure to the data to identify inconsistencies and problems for potential users. As a general procedure, the FIS QA consisted of examining the maximum, minimum, average, and standard deviation for each numerical field in the data table. An attempt was made to find an explanation for unexpected high or low values, values outside of the normal physical range for a variable, or standard deviations that appeared inconsistent with the mean. In some cases, histograms were examined to determine whether outliers were consistent with the shape of the data distribution.

The discrepancies which were identified are reported as problems in the Errors Section.

Data Verification by Data Center:

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.

11. Notes:

Limitations of the Data:

Not available.

Known Problems with the Data:

None.

Usage Guidance:

This data set could 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 could be used with caution in similar prairie landscapes to compare remote sensing derived soil moisture and field measured soil moisture.

Any Other Relevant Information about the Study:

None.

12. Application of the Data Set:

This data set could be used in conjunction with other soil moisture data to validate the soil moisture values predicted by the airborne remote sensing instruments during FIFE.

13. Future Modifications and Plans:

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.

14. Software:

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.

15. Data Access:

Contact Information:

ORNL DAAC User Services
Oak Ridge National Laboratory
Telephone: (865) 241-3952
FAX: (865) 574-4665
Email: ornldaac@ornl.gov

Data Center Identification:

ORNL Distributed Active Archive Center
Oak Ridge National Laboratory
USA

Telephone: (865) 241-3952
FAX: (865) 574-4665

Email: ornldaac@ornl.gov

Procedures for Obtaining Data:

Users may place requests by telephone, electronic mail, or FAX. Data is also available via the World Wide Web at http://daac.ornl.gov.

Data Center Status/Plans:

FIFE data are available from the ORNL DAAC. Please contact the ORNL DAAC User Services Office for the most current information about these data.

16. Output Products and Availability:

The Neutron Probe Soil Moisture data are available on FIFE CD-ROM Volume 1. The CD-ROM file name is as follows:

\DATA\SOILMSTR\SM_NEUT\GRIDxxxx\Yyyyy\ydddgrid.SMN

Where xxxx is the four digit code for the location within the FIFE site grid, yyyy are the four digits of the century and year (e.g. 1987). 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 (e.g. 061 = sixty-first day in the year). The filename extension (.sfx), identifies the data set content for the file (see the Data Characteristics Section) and is equal to .SMN for this data set.

17. References:

Satellite/Instrument/Data Processing Documentation.

Gardner, W.H. 1986. Water content. p.493-544. In: A. Klute (ed.) Methods of Soil Analysis. Part 1. Physical and mineralogical methods, 2nd ed. Agronomy Monogr. 9. ASA and SSSA, Madison, WI.

Journal Articles and Study Reports.

Carroll, T.R. 1981. Airborne soil moisture measurement using natural terrestrial gamma radiation. Soil Science, 132:358-366.

Carroll, T.R., and E.L. Peck. 1988. Airborne time-series measurements of soil moisture using terrestrial gamma radiation. Proc. Am. Congr. Sur. Map. and Am. Soc. for Photogram. & Rem. Sens, St. Louis, MO.

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.

Gogineni, S. 1990. Radar measurements of soil moisture over the Konza prairie. AMS Symposium on the First ISLSCP Field Expt., Anaheim, CA.

Olgaard, P.L. 1965. On the theory of the neutronic method for measuring the water content of soil. Danish Atomic Energy Comm., Reso. Rep. 97.

Peck, E.L., T.R. Carroll, and D.M. Lipinski. 1990. Airborne gamma radiation soil moisture measurements over short flight lines. AMS Symposium on the First ISLSCP Field Expt., Anaheim, CA.

Schmugge, T.J. 1978. Remote sensing of surface soil moisture. J. Appl. Meteorol. 17:1547-1557.

Schmugge, T.J., J.M. Meneely, A. Rango, and R. Neff. 1977. Satellite microwave observations of soil moisture variations. Bull. of Water Resources, 13:265.

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.

Wang, J.R., J.C. Shiue, E.T. Engman, and T.J. Schmugge. 1988. The soil moisture variations of two small watersheds in Konza prairie as estimated from the L-band radiometric measurements. Geophys. Res. Lett. (in review).

Wang, J.R., J.C. Shiue, E.T. Engman, and T.J. Schmugge. 1988. The soil moisture mapping with L-band pushbroom microwave radiometer in FIFE. AGU EOS (in review).

Wang, J.R., and J.C. Shieu. 1989. Remote sensing of soil moisture variations with PBMR. AGU EOS, 70(issue 15), No. 347.

Wetzel, P.J., and J.T. Chang. 1987. Concerning the relationship between evapotranspiration and soil moisture. J. Clim. Appl. Meteor.

Archive/DBMS Usage Documentation.

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 the Data Center Identification Section). Documentation about using the archive and/or online access to the data at the ORNL DAAC is not available at this revision.

18. Glossary of Terms:

A general glossary for the DAAC is located at Glossary.

19. List of Acronyms:

CD-ROM Compact Disk-Read Only Memory DAAC Distributed Active Archive Center EOS-DIS Earth Observing System-Data and Information System FIFE First ISLSCP Field Experiment FIS FIFE Information System ISLSCP International Satellite Land Surface Climatology Project ORNL Oak Ridge National Laboratory URL Uniform Resource Locator UTM Universal Transverse Mercator

A general list of acronyms for the DAAC is available at Acronyms.

20. Document Information:

April 26, 1994 (citation revised on October 15, 2002).

Warning: This document has not been checked for technical or editorial accuracy by the FIFE Information Scientist. There may be inconsistencies with other documents, technical or editorial errors that were inadvertently introduced when the document was compiled, or references to preliminary data that were not included on the final CD-ROM.

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.

Document Review Date:

February 18, 1996.

Document ID:

ORNL-FIFE_SM_NEUT.

Citation:

Cite this data set as follows:

Kanemasu, E. T. 1994. Soil Moisture Neutron Probe 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. doi:10.3334/ORNLDAAC/111. 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).

Document Curator:

DAAC Staff

Document URL:

http://daac.ornl.gov