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Data Set ID:
NSIDC-0203

SMEX02 Sliced Core Soil Moisture Data, Walnut Creek Watershed, Iowa, Version 1

This data set includes sliced soil core moisture data collected during the Soil Moisture Experiment 2002 (SMEX02).

This is the most recent version of these data.

Parameter(s):
  • SOILS > SOIL BULK DENSITY
  • SOILS > SOIL BULK DENSITY > SOIL MOISTURE/WATER CONTENT
  • SOILS > SOIL MOISTURE/WATER CONTENT
Data Format(s):
  • ASCII Text
  • Microsoft Excel
Spatial Coverage:
N: 41.99, 
S: 41.93, 
E: -93.53, 
W: -93.66
Platform(s):GROUND-BASED OBSERVATIONS
Spatial Resolution:Not SpecifiedSensor(s):SEDIMENT CORERS
Temporal Coverage:
  • 25 June 2002 to 19 July 2002
Version(s):V1
Temporal ResolutionNot specifiedMetadata XML:View Metadata Record
Data Contributor(s):Charles Laymon

Geographic Coverage

Download Via HTTPS: An Earthdata Login account is required to access these data.

Once you have logged in, you will be able to click and download files via a Web browser. There are also options for downloading via a command line or client. For more detailed instructions, please see Options Available for Bulk Downloading Data from HTTPS with Earthdata Login.

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.

Laymon, C. 2004. SMEX02 Sliced Core Soil Moisture Data, Walnut Creek Watershed, Iowa, 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/FE3UHTIWAOHV. [Date Accessed].

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Detailed Data Description

Format

Data are provided as 13 ASCII text files and as a Microsoft Excel file with 13 worksheets.

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File Naming Convention

The text files use the following naming convention:WCxx_yy.txt
where:
WC = Walnut Creek watershed
xx = the number of the study field
yy = gravimetric soil moisture (GSM), bulk density (BD), or Means

For example, the file "WC23_GSM.txt" contains GSM data from samples taken in field number 23.

The files (and Excel file worksheets), are named as follows: 
"Tare" contains tare weights prior to and after oven drying.
"WC15_GSM" contains data for all samples for site WC15. 
"WC15_Means" contains mean GSM for each day and field position for site WC15.
"WC15_BD" contains calculations of bulk density for site WC15. 
WC16-24 files contain the same types of data as the WC15 files for sites WC16, WC23, and WC24.

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File Size

The Excel file size is 888 KB. The text files range from 31 to 47 KB.

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Volume

Total volume is approximately 1 MB.

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Spatial Coverage

Southernmost Latitude: 41.93
Northernmost Latitude: 41.99
Westernmost Longitude: -93.66
Easternmost Longitude: -93.53

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Temporal Coverage

Sites 15 and 16: 25 June 2002 to 12 July 2002.
Sites 23 and 24: 25 June 2002 to 19 July 2002.

Temporal Resolution

Cores were taken on a near-daily basis at all four sites during the study period.

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Parameter or Variable

Parameter Description

Parameters of the study are gravimetric soil moisture and soil bulk density.

Parameter Range

The following tables detail the column headings for each of the four types of files (or Excel worksheets).

This first table describes the columns in the file "TARE." These data pertain to a set of 50 tares (paper bags) weighed at the beginning of the experiment.

Column heading Description
Initial weight Weight (g) of tare prior to oven drying
Dry weight Weight (g) of tare after oven drying
Change Change in tare weight (g) due to oven drying

The next table describes the columns found in the files with a "GSM" suffix. These contain data for all samples for the particular site. Following the data for each day in these worksheets are the daily means.

Column heading Description
Sample ID ID for soil sample (see note 1 below)
Day of Year Numerical day of the year
Depth Depth at midpoint of soil layer (cm)
Site Site number (15, 16, 23 or 24)
Location Location within the field site (1-6)
Wet weight Weight (g) of soil and tare prior to drying
Wet soil weight Weight (g) of soil alone prior to drying (See note 2 below)
Dry weight Weight (g) of soil and tare after drying
Net dry weight of soil Weight (g) of soil alone after drying
Dry tare weight Weight of tare after drying (See note 3 below)
Weight H20 Weight (g) of water lost from soil during drying
GSM Gravimetric soil moisture (%) for sample
Core Mean GSM Mean GSM (%) for the six 1 cm slices composing each 0-6 cm core

The following table describes the files that have a "Means" suffix. These contain mean GSM values by location within the site, and by layer, for each day:

Column heading Description
Day of Year Numerical day of the year
1, 2, 3, 4, 5, 6 Daily core mean GSM (%) for locations 1-6 at the site
0.5, 1.5, 2.5, 3.5, 4.5, 5.5 Daily mean GSM (%) by soil layer, header gives midpoint of layer (cm)
0-6 cm mean Daily core mean GSM (%) for all locations at the site

The following table describes the files that have a "BD" suffix contain data used to calculate soil bulk density for the site. These data repeat the data from "WC15_GSM" for cores that were deemed acceptable for bulk density determination.

Column heading Description
Sample ID ID for soil sample (See note 1 below)
Day of Year Numerical day of the year
Depth Depth at midpoint of soil layer (cm)
Wet weight Weight (g) of soil and tare prior to drying
Wet soil weight Weight (g) of soil alone prior to drying. See note 2 below.
Dry weight Weight (g) of soil and tare after drying
Net dry weight of soil Weight (g) of soil alone after drying
Weight H20 Weight (g) of water lost from soil during drying
GSM Gravimetric soil moisture (%) for sample
Bulk Density Bulk density (g/cm3) for each sample - Following the data for each depth is the mean for the 0-6 cm core

To the right of the main data portion in the files (and worksheets) is a summary of bulk densities by layer.

Notes on data and data files:

  1. Sample ID is a unique identifier for each soil sample. The format of the ID is MDD-SSLD, where M=month, DD=day of month, SS=site number, L=location (1-6) and D=depth (1=0-1 cm, 2=1-2 cm, etc.). For example, sample 628-2312 was collected on June 28 at site 23, for location 1 and depth 2 (1-2 cm). In a few cases, a slight departure from this convention occurred. These are noted in the files.
  2. Wet soil weight is the weight of the wet soil excluding the tare. It the weight of the sample prior to oven drying minus the wet tare weight.
  3. Dry tare weight is the weight of the tare after oven drying. On the first day of the experiment, for sites 15 and 16, duct tape was used to keep the bags sealed. In these cases, the actual pre- and post-drying weights were recorded. Otherwise, duct tape was not used, and it was determined that mean wet and dry tare weights were accurate. These weights are calculated in the file "Tare" and used throughout the data in the GSM calculations.

Sample Data Record

The following is a sample from the data file "WC15_GSM.txt":

Sample ID Day of Year Depth (cm) Site Location Wet
weight (g)		 Wet soil 
weight (g)		 Dry weight (g) Net dry weight 
of soil (g)		 Dry tare 
weight (g)		 Weight H2O 
(g)		 GSM (%) Core Mean
GSM (%)
625-1511 176 0.5 15 1 36.944 27.105 36.006 26.665 9.341 0.440 1.65
625-1512 176 1.5 15 1 33.258 23.160 32.241 22.641 9.600 0.519 2.29
625-1513 176 2.5 15 1 33.979 23.977 32.711 23.207 9.504 0.770 3.32
625-1514 176 3.5 15 1 33.273 23.437 31.272 21.934 9.338 1.503 6.85
625-1515 176 4.5 15 1 37.498 27.603 34.559 25.162 9.397 2.441 9.70
625-1516 176 5.5 15 1 32.424 22.516 29.771 20.361 9.410 2.155 10.59 5.73
 
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Software and Tools

Microsoft Excel is required to view the spreadsheet file. A word-processing program or Web browser is sufficient for viewing the text files.

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Data Acquisition and Processing

Derivation Techniques and Algorithms

Error Sources

Missing and erroneous data were identified based on field notes and post-experiment examination. These data are indicated by (X) and highlighted in grey in the Excel spreadsheet. Errors in soil weights, and consequently GSM and bulk density estimates, are due to weighing (generally on the order of .01 g) and loss of soil before or after oven drying. The errors found after drying were noted in the data files and corrected to the extent possible in the GSM and bulk density calculations. Cells highlighted in yellow are samples for which dry weight values adjustments were made.

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Sensor or Instrument Description

The 0-6 cm soil moisture profile was measured using a standard soil core sampler, the barrel of which was loaded with one or more metal cylinders and hammered into the soil. Following extraction of the sampler, the cylinder, containing the soil sample, was removed from the barrel. The metal cylinders were 1 cm thick to obtain high-resolution surface moisture profiles. Following extraction, each core was sliced with a wide blade at 1 cm intervals and each was analyzed separately (see the figure below). If soil moisture conditions were favorable and the soil was relatively free from gravel and plant residue, the sample was suitable for determining bulk density.

Six cores were taken each day at each field site. Three of these were taken in the vicinity of the flux tower at each site; these are denoted locations 1-3. The other three were taken at 3 separate sampling points (locations 4-6) in the field.

Photograph of researcher separating 1 cm sections of soil core

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References and Related Publications

Please see the SMEX02 site for more information, and the NSIDC SMEX site to access data.

Contacts and Acknowledgments

Charles Laymon and Ashutosh Limaye, Hydrologists
William Crosson, Meteorologist
Universities Space Research Association, National Space Science and Technology Center, Global Hydrology and Climate Center, Marshall Space Flight Center, Huntsville, Alabama

Frank Archer, Soil Scientist
Alabama A&M University, Normal, Alabama

Acknowledgments: 

The investigators wish to thank all who helped collect and process the field data, including: Andrew Manu and Brian Schmid from Iowa State University, Daniel Manu from Auburn University, Thomas Coleman, Jr. from Alabama A&M University, and Alfredo Perez from Texas A&M University, Kingsville.

Document Information

DOCUMENT CREATION DATE

December 2003

No technical references available for this data set.

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