This data set includes sliced soil core moisture data collected during the Soil Moisture Experiment 2002 (SMEX02).
SMEX02 Sliced Core Soil Moisture Data, Walnut Creek Watershed, Iowa, Version 1
This is the most recent version of these data.
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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].Detailed Data Description
Data are provided as 13 ASCII text files and as a Microsoft Excel file with 13 worksheets.
The text files use the following naming convention:WCxx_
where:
WC = Walnut Creek watershed
xx = the number of the study field
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.
The Excel file size is 888 KB. The text files range from 31 to 47 KB.
Total volume is approximately 1 MB.
Southernmost Latitude: 41.93
Northernmost Latitude: 41.99
Westernmost Longitude: -93.66
Easternmost Longitude: -93.53
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.
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:
- 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.
- 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.
- 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 |
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.
Data Acquisition and Processing
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.
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.
References and Related Publications
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
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