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CLPX-Ground: ISA Soil Moisture Measurements

Summary

This data set consists of in-situ point measurements of soil moisture within three 25-km by 25-km Meso-cell Study Areas (MSAs) in northern Colorado (Fraser, North Park, and Rabbit Ears). Measurements were made between September 2001 and April 2003. Spatial and temporal variations in soil moisture described by these data may be used to support remotely sensed airborne (e.g., Gamma flights) and satellite (e.g., AMSR-E) surveys of soil moisture at increasing spatial scales. Gravimetric measurements, as well as some volumetric measurements, of soil moisture were made at each measurement site.

The NASA Cold Land Processes Field Experiment (CLPX) is a multi-sensor, multi-scale experiment that focuses on extending a local-scale understanding of water fluxes, storage, and transformations to regional and global scales. Within a framework of nested study areas in the central Rocky Mountains of the western United States, ranging from 1-ha to 160,000 km2, intensive ground, airborne, and spaceborne observations are collected. Data collection focuses on two seasons: mid-winter, when conditions are generally frozen and dry, and early spring, a transitional period when both frozen and thawed, dry and wet conditions are widespread.

Citing These Data

Cline, D. and K. Elder. 2004. ISA Soil Moisture Measurements. Boulder, CO: National Snow and Ice Data Center. Digital Media.

Overview Table

Category Description
Data format Comma-separated ASCII
Spatial coverage MSAs within the CLPX Small Regional Study Area (SRSA), northern Colorado
Temporal coverage and resolution September 2001 through April 2003
Total File size Data files range from 16 to 129 KB. Photos are appx 600-700 KB each.
Parameter(s) Bulk density, gravimetric water content, and volumetric water content
Procedures for obtaining data Data are available via FTP

Table of Contents

1. Contacts and Acknowledgements
2. Detailed Data Description
3. Data Access
4. Data Acquisition
5. Document Information

1. Contacts

Investigator(s) Name and Title

Dr. Kelly Elder
USFS Rocky Mountain Research Station
USDA Forest Service
240 West Prospect Rd.
Fort Collins, CO 80526

Dr. Don Cline
NOHRSC
National Weather Service, NOAA
1735 Lake Drive West
Chanhassen, MN 55317

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

2. Detailed Data Description

Format

ASCII data in all files other than the met_sites file are presented in 35 columns in comma-separated value format. Double quotes are used to delimit text within fields, and commas contained within the double quotes do not indicate a new field. Column headers are included in row 1 and are as follows:

Sample Number
Sample ID
Date
Time (MDT)
Latitude (DD)
Latitude (MM)
Latitude (SS)
Longitude (DDD)
Longitude (MM)
Longitude (SSS)
Latitude (DD.DDDD)
Longitude (DD.DDDD)
UTM east
UTM North
Remarks / Comments
Flight line 1
Flight line 2
Flight line 3
Principal Collector
Partner
Photo (south facing & north facing)
Sample A container weight or bag weight (g)
Sample A Wet Weight (g)
Sample A Dry Weight (g)
Sample A moisture (g)
Sample A dry soil (g)
Sample A Gravimetric (g H2O/g soil)
Sample depth (cm unless otherwise stated)
Sample B container weight or bag weight (g)
Sample B Wet Weight (g)
Sample B Dry Weight (g)
Sample B moisture (g)
Sample B dry soil (g)
Sample B Gravimetric (g H2O/g soil)
Sample depth (cm unless otherwise stated)

ASCII data in the Soil_moisture_met_sites file are presented in 12 columns in comma-separated value format. Double quotes are used to delimit text within fields, and commas contained within the double quotes do not indicate a new field. Column headers are included in row 1 and are as follows:

Sample ID
UTM east
UTM North
Date
Time (MDT)
Total sample wet mass (g)
Total sample dry mass (g)
Bulk density (g/cm3)
Sample gravimetric water content (g H2O/g soil)
Sample volumetric water content (g H2O/g soil)
Sample depth (cm unless otherwise stated)
Remarks / Comments

Sample Number is determined by

Sept2001: MSA sample number.
IOP3: either (1) location, or (2) replicate number / sample number.
IOP 4: replicate number and sample number.
IOP1, IOP2, and Sept2002 have no sample numbers; only sample IDs

Sample IDs use the following conventions:

Sept2001: MQQXXX where M = MSA indicator (e.g., F = Fraser), QQ = Quadrant (i.e., NE, NW, SE, SW), and XXX = Quadrant sample number).

Sept2001: MQQXXR where M = MSA indicator (e.g., F = Fraser), QQ = Quadrant (i.e., NE, NW, SE, SW), XX = Quadrant sample number, and R = Sample replicate (i.e., A or B).

IOP1 & IOP2: one of three options:
(1) MISPXX where M = MSA indicator (e.g., F = Fraser), I = ISA indicator (e.g., A = Alpine), SP = snow pit, and XX = snow pit number in which the sample was taken
(2) nameX where name = surveyor name, and X = surveyor sample number
(3) LSOSXR where LSOS = sampling location, X = LSOS sample number, and R = Sample replicate (i.e., a or b).

IOP3: one of four options:
(1) name of MSA (e.g., Fraser)
(2) MIMET where M = MSA indicator (e.g., F = Fraser), I = ISA indicator (e.g., A = Alpine), and MET = Main meteorological site at which the sample was taken
(3) MISP where M = MSA indicator (e.g., F = Fraser), I = ISA indicator (e.g., A = Alpine), and SP = snow pit
(4) LSOS = sampling location.

IOP4: one of four options:
(1) MISP where M = MSA indicator (e.g., F = Fraser), I = ISA indicator (e.g., A = Alpine), and SP = snow pit
(2) LSOS = sampling location
(3) MIMET where M = MSA indicator (e.g,. F = Fraser), I = ISA indicator (e.g., A = Alpine), and MET = Main meteorological site at which the sample was taken

met_sites: MI-X where M = MSA indicator (e.g., F = Fraser), I = ISA indicator (e.g., A = Alpine), and X is the position of the meteorological tower within the ISA (i.e., C = center, NW = northwest corner, NE = northeast corner, SW = southwest corner and SE = southeast corner).

FHQ indicates a met tower located close to the LSOS outside of other Fraser ISAs.

Date follows the following conventions:

IOP1: YYYYMMDD
IOP2: YYYYMMDD
IOP3: MM-DD-YY
IOP4: YYYYMMDD
met_sites: DD/M/YYYY
Sept2001: YYMMDD
Sept2002: M/DD/YYYY

Directory Structure

The directory structure is as follows:

IOP1/
  Soil_moisture_IOP1_v1.csv
IOP2/
  Soil_moisture_IOP2_v1.csv
IOP3/
  Soil_moisture_IOP3_v1.csv
IOP4/
  Soil_moisture_IOP4_v1.csv
Met_Sites/
  Soil_moisture_met_sites_v1.csv
Sept_2001/
  Soil_moisture_Sept2001_v1.csv
Sept_2002/
  Photos/
  Soil_moisture_Sept2002_v1.csv

File Naming Convention

The data files are named Soil_moisture_###_v1.csv where:

### = IOP1, IOP2, IOP3, IOP4, met_sites, Sept2001, Sept2002
v1 = version number

Photos of sample sites taken during the Fall background data collection in 2002 are named MQQ###S.jpg where:

M = MSA
QQ – Quadrant of MSA (i.e. NE, NW, SE or SW)
### = three digit sample number
S = sample replicate (A or B)

The location of photographs is determined using the label of a soil sample container placed in the foreground of photograph. If the clarity of the label in the photograph prevents an accurate identification of the location, the photograph is included in the directory but not labeled in the manner described above.

File Size

Data files range from 16 to 129 KB. Photos are appx 600-700 KB each.

Spatial Coverage

Three data sampling programs contributed to the overall soil moisture data set:

    1. Fall background data
    2. Snow pit data
    3. Meteorological tower installation data

1. Fall Background Data:

Soil moisture data were collected during September of 2001 and 2002 to provide measurements of soil moisture prior to the beginning of the winter snow accumulation season. Soil samples were collected at between 77 and 146 separate sites within each MSA. The location of each sample within each MSA is recorded in latitude and longitude to four decimal places. Where possible, samples were located within MSAs to intersect the ground path of the gamma data collection flight lines, thereby allowing calibration of background gamma data. The ID number of the gamma flight lines are listed where appropriate intersections occur. Photographs were taken at each site during 2002 to record the nature of the terrain and vegetation surrounding the point samples.

2. Snow Pit Data:

Soil samples were taken at the base of snow pits that were excavated at up to 16 locations within each ISA during IOP1, IOP2, IOP3, and IOP4. The location of each pit within a 1 km x 1 km ISA was consistent between ISAs. The following figure shows the location of snow pits (see blue crosshair style pit markers; e.g., NMSP1) in the example ISA.

The location of snow pits in the LSOS in 2002 are indicated below. Soil samples were taken at the base of each pit during IOP1 in February and IOP2 in March.

The location of snow pits in the LSOS in 2003 are indicated below. Soil samples were taken at the base of each pit during IOP3 in February and IOP4 in March.

In the North Park MSA, additional samples were collected throughout the entire MSA, where possible, to intersect the ground path of the gamma data collection flight lines. Exact locations of each sample are recorded as UTM east and UTM north, datum WGS84, zone 13.

3. Meteorological Tower Installation Data:

Soil samples were collected during the installation of soil probes near the base of meteorological towers during August and September 2002. Five towers were located in each ISA, one close to each of the four corners and one close to the center. Exact locations are recorded as UTM east and UTM north, datum WGS84, zone 13.

Spatial Coverage Map:

The following map shows the CLPX study area:

Temporal Coverage

The IOP1 and IOP2 (2002) sampling schedules were:

Feb. 19, 21 and 23: Pits 1, 3, and 5
Feb. 20, 22 and 24: Pits 2, 4, and 6

Mar. 25, 27 and 29: Pits 2, 4, and 6
Mar. 26, 28 and 30: Pits 1, 3, and 5

The IOP3 and IOP4 (2003) sampling schedules were:

Feb. 19, 21 and 23: Pits 2, 4, and 6
Feb. 20, 22 and 24: Pits 1, 3, and 5

Mar. 25, 27 and 29: Pits 2, 4, and 6
Mar. 26, 28 and 30: Pits 1, 3, and 5

Soil moisture data were collected during September of 2001 and 2002 to provide measurements of soil moisture prior to the beginning of the winter snow accumulation season. Soil samples were collected during the installation of soil probes near the base of meteorological towers during August and September 2002.Photographs were taken at each site during 2002 to record the nature of the terrain and vegetation surrounding the point samples.

Parameter or Variable

Parameters presented in this data set are bulk density (g/cm3), gravimetric water content (g H2O/g soil), and volumetric water content (g H2O/g soil) at meteorological sites, and gravimetric water content (g H2O/g soil) at all other sites.

Not all of the sampling programs collected information for each of the 35 parameters. To maintain consistency, for all files other than the met_sites file, all 35 parameters are included in each file whether data were collected or not. The met_sites file introduced two new parameters and did not use 25 other parameters previously used. The following table provides an overview of which parameters are available for the different sampling programs, and shows an ‘x' where a parameter was collected, a blank where a parameter was not collected, and an ‘N/A' where the parameter is not present in the file.

Parameter

Sep 2001

Sep 2002

IOP1

IOP2

IOP3

IOP4

met_sites

Sample Number *

x

 

 

 

x

x

N/A

Sample ID *

x

x

x

x

x

x

x

Date *

x

x

 

 

x

 

X

Time (MDT)

x

x

 

 

 

 

X

Lat (DD)

x

 

 

 

 

 

N/A

Lat (MM)

x

 

 

 

 

 

N/A

Lat (SS)

x

 

 

 

 

 

N/A

Long (DDD)

x

 

 

 

 

 

N/A

Long (MM)

x

 

 

 

 

 

N/A

Long (SSS)

x

 

 

 

 

 

N/A

Latitude (DD.DDDD)

x

x

 

 

 

 

N/A

Longitude (DD.DDDD)

x

x

 

 

 

 

N/A

UTM east

 

 

x

x

 

 

X

UTM North

 

 

x

x

 

 

x

Remarks / Comments

x

x

 

 

 

 

x

Flight line 1

x

 

 

 

 

 

N/A

Flight line 2

x

 

 

 

 

 

N/A

Flight line 3

x

 

 

 

 

 

N/A

Principal Collector

x

x

x

X

x

x

N/A

Partner

x

x

 

 

x

x

N/A

Photo (south facing & north facing)

 

x

 

 

 

 

N/A

Sample A container weight or bag weight (g)

 

x

x

x

x

x

N/A

Sample A Wet Weight (g)

x

x

x

x

x

x

x

Sample A Dry Weight (g)

x

x

x

x

x

x

x

Sample A moisture (g)

 

x

 

 

x

x

N/A

Sample A dry soil (g)

 

x

 

 

x

x

N/A

Sample A Gravimetric (g H2O/g soil)

x

x

x

x

x

x

x

Sample depth (cm unless otherwise stated)

 

x

 

 

x

 

x

Sample B container weight or bag weight (g)

 

x

x

x

x

x

N/A

Sample B Wet Weight (g)

x

x

x

x

x

x

N/A

Sample B Dry Weight (g)

x

x

x

x

x

x

N/A

Sample B moisture (g)

 

x

 

 

x

x

N/A

Sample B dry soil (g)

 

x

 

 

x

x

N/A

Sample B Gravimetric (g H2O/g soil)

x

x

x

x

x

x

N/A

Sample depth (cm unless otherwise stated)

 

x

 

 

 

 

N/A

Bulk density (g/cm3)

N/A

N/A

N/A

N/A

N/A

N/A

X

Sample volumetric content (g H2O/g soil)

N/A

N/A

N/A

N/A

N/A

N/A

X

* - format varies

Some inconsistencies exist in the format in which parameters were recorded.

Quality Assessment

Any missing values in the data were replaced by a default value of 9999.

Remarks in the original data sheets had commas and speech marks that may be confused for column delimiters. The following punctuation was changed:

,

changed to

-

“

changed to

inches

@

changed to

at

;

changed to

-

3. Data Access

Data Access

Data are available via FTP at ftp://sidads.colorado.edu/pub/DATASETS/CLP/data/ground_data/nsidc0178_soil_moisture/

Related Data Collections

All CLPX Data Sets
CLPX IOP Snow Pit Data
CLPX-Snow Measurements at the Local Scale Observation Site (LSOS)

4. Data Acquisition

Two types of soil samples were taken. At all sites other than meteorological sites, soil samples were made vertically into the ground surface to a depth of 20 cm using a 2.3-cm-diameter hand auger. If the auger was not able to penetrate 20 cm into the ground, the depth of the sample was recorded separately. The sample was then removed from the auger and transferred into an airtight container. A second, replicate sample was made at each site where samples were collected using an auger. Only gravimetric soil moisture measurements were made on samples collected using an auger.

At meteorological sites, permanent soil moisture/temperature probes were installed at 5 cm, 20 cm and 50 cm below the ground surface. During installation of these probes, soil moisture samples were taken at each of these levels, and also at 2.45 cm from the surface. Soil samples were made by forcing a circular ring (4.90 cm in diameter and 2.45 cm deep) into the pit wall, with the center point of the ring at each of the four depth levels. The plug of soil within the ring was then removed along with the ring and sealed in an airtight can. Gravimetric measurements of soil moisture were made for each sample by dividing the difference between the weight of the dry and wet samples by the weight of the dry sample. Volumetric measurements of soil moisture were also made by multiplying the gravimetric moisture content by the ratio of the bulk density of an undisturbed soil sample and the density of water.

The following equations describe how gravimetric and volumetric soil moisture content are calculated:

w = gravimetric moisture content
Mw = mass of the wet sample
Md = mass of the dry sample
θ = volumetric moisture content
ρ = density of water
ρb = bulk density of sample

5. Document Information

List of Acronyms

CLPX = NASA Cold Land Processes Field Experiment
IOP = Intensive Observation Period
ISA = Intensive Study Area
LRSA = Large Regional Study Area
LSOS = Local Scale Observation Site
MSA = Meso-cell Study Area

Document Creation Date

January 4, 2004

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