CLPX-Ground: ISA Snow Pit Measurements, Version 2.0

Summary

This data set consists of snow pit data from nine study areas, within three larger-scale areas in northern Colorado (Fraser, North Park, and Rabbit Ears Meso-cell study Areas (MSAs)). The study areas range from low-relief (flat topography) unforested areas with shallow snow covers, to high-relief (complex topography) densely forested areas with deep snow covers. Parameters measured include snow density, snow temperature, snow stratigraphy, and snow grain size. Data were collected during February and March 2002 and 2003. This data set is part of the NASA Cold Land Processes Field Experiment (CLPX).

The NASA 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

Elder, K. and D. Cline. 2003, updated 2004. CLPX-Ground: ISA Snow Pit Measurements. Version 2. [indicate subset used]. Edited by M. Parsons and M. Brodzik. Boulder, Colorado USA: NASA DAAC at the National Snow and Ice Data Center. http://dx.doi.org/10.5060/D4H41PBP.

Overview Table

Category Description
Data format Comma-separated ASCII files and shapefiles
Spatial coverage Fraser, North Park, and Rabbit Ears MSAs in northern Colorado, US
Temporal coverage and resolution 19-24 February and 25-30 March 2002
20-25 February and 26-31 March 2003
File size ASCII file sizes range from 20 to 300 KB. shapefile sizes range from 1 to 8 MB.
Parameter(s) Snow Density
Snow Temperature
Snow Stratigraphy
Snow Grain Size
Snow Water Equivalent
Data access Data are available via FTP

Table of Contents

1. Contacts
2. Detailed Data Description
Format
File and Directory Structure
File Naming Convention
File Size
Spatial Coverage
Temporal Coverage
Parameters
Quality Assessment
3. Data Access and Tools
4. Data Acquisition and Processing
5. References and Related Publications
6. Document Information

1. Contacts

Investigator(s) Name and Title

Kelly Elder
Research Hydrologist
Rocky Mountain Research Station
USDA Forest Service
240 W. Prospect Road
Fort Collins, CO USA 80526

Don Cline
National Weather Service
National Operational Hydrologic REmote Sensing Center
1735 Lake Drive W.
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

Snow pit data are available in comma-separated ASCII text files, with a file extension of .csv, and in shapefile spatial data format shapefiles, with various extensions. There are four types of files: summary, density profile, temperature, and stratigraphy. shapefiles contain everything included in the text files, except for general pit comments, which were too verbose for import into shape format.

During all Intensive Study Periods (IOPs), extra pits were dug across the entire North Park MSA, to coincide with simultaneous airborne gamma measurements. These pits have non-standard pit IDs.

Missing data in the ASCII files are identified by "-999". Double quotes are used to delimit text within fields, and commas contained within the double quotes do not indicate a new field. In the shapefiles, missing dates are designated 9999-99-99, missing text fields are designated "NoData", and missing numeric fields are designated -999.

For detailed information about snow pit data format, please see the CLPX Snow Pit Measurements documentation.

File and Directory Structure

Data are organized in the following structure:

pit_iop_v2.tgz  
              
photos/
   iop1/
     alpine/
	    other/
		roughness/
		terrain/
	 buffalo_pass/
	 fool_creek/
	 gamma/
	 illinois_river/
	 michigan_river/
	 potter_creek/
	 spring_creek/
	 st_louis_creek/  
	 
   iop2/
     alpine/
	    other/
		roughness/
		templates/
		terrain/
	 buffalo_pass/
	 fool_creek/
	 illinois_river/
	 michigan_river/
	 no_isa/
	 potter_creek/
	 spring_creek/
	 st_louis_creek/
	 walton_creek/
	 
   iop3/
     alpine/
	    other/
	    pitwall/
	    roughness/
	    terrain/
	 buffalo_pass/
	 fool_creek/
	 illinois_river/
	 michigan_river/
	 potter_creek/
	 spring_creek/
	 st_louis_creek/  
	 
   iop4/

The compressed (tarred and zipped) file "pit_iop_v2.tgz" will extract into two directories: ascii/ contains the .csv version of the data, and shape_files/ contains the GIS-compatible shapefiles. The shapefiles are organized as:

pit_iop_v#_density.dbf (and .prj, .sbn, .sbx, .shp, .shx)
pit_iop_v#_strat.dbf (and .prj, .sbn, .sbx, .shp, .shx)
pit_iop_v#_summary.dbf (and .prj, .sbn, .sbx, .shp, .shx)
pit_iop_v#_temperature.dbf (and .prj, .sbn, .sbx, .shp, .shx)

Please see the "Data Set Version History" section of the CLPX Snow Pit Measurements document for information about the latest version release (v#).

File Naming Convention

Snow pit filenames are named pit_GROUP_v#_DATA.csv, where:

pit indicates snow pit data
GROUP = pit group (iop1, iop2, iop3, iop4)
v# = Data release number (e.g., version 2)
DATA = type of data in the file: "summary," "density," "temperature," or "strat"
.csv = comma-separated value text file

shapefile names are pit_GROUP_v#_DATA.ext, where:

pit = indicates snow pit data
GROUP = pit group (iop)
note that all IOP pits are included in a single shape file
v# = Data release number (e.g., version 2)
DATA = type of data in the file: "summary," "density," "temperature," or "strat"
.ext = shape file extenstions {.dbf, .prj, .sbn, .sbx, .shp, .shx}

Please see the "Data Set Version History" section of the CLPX Snow Pit Measurements document for information about the latest version release.

The following codes are used in filenames (and for site names in the raw data):

  MSA Code 
        F = Fraser
        N = North Park
        R = Rabbit Ears

  ISA Code 
        A = Alpine
        B = Buffalo Pass
        F = Fool Creek
        I = Illinois River
        M = Michigan River
        P = Potter Creek
        S = Spring Creek (if MSA Code = R) or
                St. Louis Creek (if MSA Code = F)
        W = Walton Creek

  ISA Sector 
        A = Lower Left Quadrant - SW
        B = Upper Left Quadrant - NW
        C = Upper Right Quadrant - NE
        D = Lower Right Quadrant - SE

File Size

ASCII file sizes range from 20 to 300 KB. shapefile sizes range from 1 to 8 MB.

Spatial Coverage

Fraser, North Park, and Rabbit Ears MSAs in northern Colorado, USA.

Schematic diagram of the nested study areas for the CPLX
Study area map
Location of MSAs
Location and characteristics of ISAs

IOP1 Snow Pits Measured:

MSA Planned number of pits Actual number of pits
Fraser 48 47
LSOS (18 pits) 0 0
North Park 48 48 plus 118 "gamma" pits
Rabbit Ears 48 48

IOP2 Snow Pits Measured:

MSA Planned number of pits Actual number of pits
Fraser 48 48
LSOS (18 pits) 0 0
North Park 48 48 plus 160 "gamma" pits
Rabbit Ears 48 48

IOP3 Snow Pits Measured:

MSA Planned number of pits Actual number of pits
Fraser 48 48
North Park 48 48 plus 92 "gamma" pits
Rabbit Ears 48 18

IOP4 Snow Pits Measured:

MSA Planned number of pits Actual number of pits
Fraser 48 48
North Park 48 48 plus 43 "gamma" pits
Rabbit Ears 48 44

Temporal Coverage

IOP1 took place 19-24 February 2002.
IOP2 took place 25-30 March 2002.
IOP3 took place 20-25 February 2003.
IOP4 took place 26-31 March 2003.

Because of the general lack of snow in North Park, all pit data were collected on the first day of ground observations. The second day, teams collected pits at sites across the entire MSA to coincide with the gamma overflights.

Parameter or Variable

Parameter Description

Parameters include snow density, snow temperature, snow stratigraphy, snow grain size, snow water equivalent, snow wetness, surface roughness, and various averages and statistics.

For a complete description of parameters and measurements, please refer to the Measurements section of the CLPX Plan.

Quality Assessment

The pit data were collected with the strictest levels of quality control, including QC performed in the field, usually within a day of the measurement (this includes the so-called "gamma pits" taken along roadsides in North Park, to coincide with simulataneous airborne gamma overflights).

Sources of measurement error in the snow pit density data include debris/vegetative matter embedded in the snow pit wall, particularly at or near the bottom of the snow pit, and the practice of "carrying down" the last measured density to the bottom of the pit, when the density cutter could not be used for the lowest measurements. This usually affected the last 10 cm or so, but could affect more, and is indicated in the density profile records with QC code "001". Surveyors did their best to avoid debris in the density cutters, but this situation was not always avoidable, and, where possible, was noted in the surveyors' comments.

Detailed Explanations of Snow Pit QC Codes:

In general:
  codes from   are reserved for QC performed on
  ----------   --------------------------------
  001-099      snow density measurements
  100-199      snow mass measurements ("shallow" pits)
  200-299      snow temperature measurements
  300-399      snow stratigraphy measurements
  400-899      unused
  900-999      general pit information, i.e. header values


Code   Description (what was reset/set/estimated: the reason why)
----   ----------------------------------------------------------
000    QC OK: all tests passed
001    Density value estimated: Surveyor did not measure densities to the ground.
002    Density value calculated from sipre mass: Surveyor used sipre tube instead of density cutter.
003    Reset recorded layer top heights: recorded layer overlapped with layer above.
004    Interpolated layer density: gap in recorded densities.
005    Surveyor entered trace, will be treated as measurement of 0.
105    Surveyor entered trace, will be treated as measurement of 0.
301    Reordered grain sizes from LargeMedSmall:  Relative grain sizes appeared out of expected order.
302    Reordered grain sizes from LargeSmallMed:  Relative grain sizes appeared out of expected order.
303    Reordered grain sizes from MedSmallLarge:  Relative grain sizes appeared out of expected order.
304    Reordered grain sizes from MedLargeSmall:  Relative grain sizes appeared out of expected order.
305    Reordered grain sizes from SmallLargeMed:  Relative grain sizes appeared out of expected order.
310    Reordered grain dimensions from LongShort:  Relative dimensions appeared out of expected order.
311    Reordered grain dims/sizes from LongShort and LargeMedSmall:  Relative grains appeared out of expected order.
312    Reordered grain dims/sizes from LongShort and LargeSmallMed:  Relative grains appeared out of expected order.
313    Reordered grain dims/sizes from LongShort and MedSmallLarge:  Relative grains appeared out of expected order.
314    Reordered grain dims/sizes from LongShort and MedLargeSmall:  Relative grains appeared out of expected order.
315    Reordered grain dims/sizes from LongShort and SmallLargeMed:  Relative grains appeared out of expected order.
320    Grain dims/sizes are ambiguous.
901    Snow pit depth estimated from first density measurement:  Surveyor did not enter pit depth.
902    Snow pit depth estimated from mass measurement depths:  Surveyor did not enter pit depth.
903    Snow pit depth estimated from first stratigraphy depth:  Surveyor did not enter pit depth.
904    Snow pit depth set to 0:  Surveyor did not enter pit depth, no snow measurement taken, but soil samples taken.
905    Warning: Snow pit depth does not match top of density profile.
906    Warning: Snow pit depth does not match top of temperature profile.
907    Warning: Snow pit depth does not match top of stratigraphy profile.
914    Canopy reset to missing value:  Snow depth is 0.
915    Surface roughness reset to n:  Snow depth is 0.
916    Surface wetness reset to missing value:  Snow depth is 0.
917    Canopy height reset to missing value:  Snow depth is 0.
950    Warning: Shallow pit form used, but pit depth > 15 cm.
951    Warning: Deep pit form used, but pit depth < 15 cm.
990    Warning: One or both UTM coordinates are missing.
991    Warning: Missing date and/or time field.
999    No data collected for this pit.

Detailed Explanations:
----------------------
000    QC OK: all tests passed

	No problems were detected, values have not been changed from the
	original forms.

Density QC codes
----------------

001    Density value estimated: Surveyor did not measure densities to the ground.

	The density cutter was 10 cm high, so the final density profile
	was generally not measured all the way to the ground, especially
	in cases where vegetation was present.  This density measurement
	was estimated by carrying the last actual measurement to the
	ground.

002    Density value calculated from sipre mass: Surveyor used sipre tube instead of density cutter.

	In some cases, the surveyor used the density profile sheet
	(normally used for density cutter measurements) to record SIPRE
	tube (mass) measurments.  The original measurement is assumed to
	be a mass and has been used to calculate this density.

003    Reset recorded layer top heights: recorded layer overlapped with layer above.

	The recorded density layer overlapped with the layer above it.  In
	order to assure non-overlapping measurements for pit average
	density and SWE, the top height of this layer was reset to the
	bottom height of the layer above it.

004    Interpolated layer density: gap in recorded densities.

	There was a gap in the recorded density layers.  In order to
	assure a continuous set of density measurements for pit average
	density and SWE, this layer was inserted, with a density
	interpolated from the densities of the immediately surrounding
	layers.

005    Surveyor entered trace, will be treated as measurement of 0.

        During IOP3 and IOP4, snow on the ground that was not measurable
        was recorded as a trace, and trace values were included in
        calculated values as zeroes.
	

Mass QC codes
----------------------

105    Surveyor entered trace, will be treated as measurement of 0.

        During IOP3 and IOP4, snow on the ground that was not measurable
        was recorded as a trace, and trace values were included in
        calculated values as zeroes.
	

Stratigraphy QC codes
----------------------

301    Reordered grain sizes from LargeMedSmall:  Relative grain sizes appeared out of expected order.

	The expected order of grain dimensions was short dimension Small,
	Medium, Large followed by long dimension Small, Medium, Large.
	However, when the QC software compared the areas (i.e. ShortSmall
	times LongSmall, etc.) the original values in this stratigraphy
	layer appeared to be reversed (Large, Medium, Small) and have been
	reordered.

302    Reordered grain sizes from LargeSmallMed:  Relative grain sizes appeared out of expected order.

	The expected order of grain dimensions was short dimension Small,
	Medium, Large followed by long dimension Small, Medium, Large.
	However, when the QC software compared the areas (i.e. ShortSmall
	times LongSmall, etc.) the original values in this stratigraphy
	layer appeared to be out of order (Large, Small, Medium) and have
	been reordered.

303    Reordered grain sizes from MedSmallLarge:  Relative grain sizes appeared out of expected order.

	The expected order of grain dimensions was short dimension Small,
	Medium, Large followed by long dimension Small, Medium, Large.
	However, when the QC software compared the areas (i.e. ShortSmall
	times LongSmall, etc.) the original values in this stratigraphy
	layer appeared to be out of order (Medium, Small, Large) and have
	been reordered.

304    Reordered grain sizes from MedLargeSmall:  Relative grain sizes appeared out of expected order.

	The expected order of grain dimensions was short dimension Small,
	Medium, Large followed by long dimension Small, Medium, Large.
	However, when the QC software compared the areas (i.e. ShortSmall
	times LongSmall, etc.) the original values in this stratigraphy
	layer appeared to be out of order (Medium, Large, Small) and have
	been reordered.

305    Reordered grain sizes from SmallLargeMed:  Relative grain sizes appeared out of expected order.

	The expected order of grain dimensions was short dimension Small,
	Medium, Large followed by long dimension Small, Medium, Large.
	However, when the QC software compared the areas (i.e. ShortSmall
	times LongSmall, etc.) the original values in this stratigraphy
	layer appeared to be out of order (Small, Large, Medium) and have
	been reordered.

310    Reordered grain dimensions from LongShort:  Relative dimensions appeared out of expected order.

	The expected order of grain dimensions was 3 short dimensions
	followed by 3 long dimensions, however, original values in this
	stratigraphy layer appeared swapped, and have been reordered.

311    Reordered grain dims/sizes from LongShort and LargeMedSmall:  Relative grains appeared out of expected order.

	A combination of 301 and 310.

312    Reordered grain dims/sizes from LongShort and LargeSmallMed:  Relative grains appeared out of expected order.

	A combination of 302 and 310.

313    Reordered grain dims/sizes from LongShort and MedSmallLarge:  Relative grains appeared out of expected order.

	A combination of 303 and 310.

314    Reordered grain dims/sizes from LongShort and MedLargeSmall:  Relative grains appeared out of expected order.

	A combination of 304 and 310.

315    Reordered grain dims/sizes from LongShort and SmallLargeMed:  Relative grains appeared out of expected order.

	A combination of 305 and 310.

320    Grain dims/sizes are ambiguous.

	The combination of dimensions and grain sizes was ambiguous.
	These grain sizes were left in the order that they were recorded,
	but should probably be treated with care before assuming dimension
	and or size order.

Pit Summary (general mismatches across various fields) QC codes
---------------------------------------------------------------

901    Snow pit depth estimated from first density measurement:  Surveyor did not enter pit depth.

	The pit depth field on the original data sheet was left blank.  It
	has been estimated using the top height of the uppermost density
	measurement.

902    Snow pit depth estimated from mass measurement depths:  Surveyor did not enter pit depth.

	The pit depth field on the original data sheet was left blank, and
	there was no density or stratigraphy profile information.  The pit
	depth has been estimated using the maximum height of the mass
	measurements taken.

903    Snow pit depth estimated from first stratigraphy depth:  Surveyor did not enter pit depth.

	The pit depth field on the original data sheet was left blank, and
	there was no density profile information.  The pit depth has been
	estimated using the top height of the uppermost stratigraphy
	measurement.

904    Snow pit depth set to 0:  Surveyor did not enter pit depth, no snow measurement taken, but soil samples taken.

	The pit depth field on the original data sheet was left blank, and
	there was no density, temperature or stratigraphy profile
	information, but soil samples were taken.  The location is assumed
	to have no snow, and depth has been set to 0.

905    Warning: Snow pit depth does not match top of density profile.

	The pit depth value on the original data sheet is different from
	the top height of the density profile.

906    Warning: Snow pit depth does not match top of temperature profile.

	The pit depth value on the original data sheet is different from
	the top height of the temperature profile.

907    Warning: Snow pit depth does not match top of stratigraphy profile.

	The pit depth value on the original data sheet is different from
	the top height of the stratigraphy profile.

914    Canopy reset to missing value:  Snow depth is 0.

	Measurement protocol was to record canopy only when snow depth was
	greater than 0.  In this case a recorded canopy was reset to
	missing because the snow depth was 0.

915    Surface roughness reset to n:  Snow depth is 0.

	Measurement protocol was to take a surface roughness photo only
	when snow depth was greater than 0.  In this case a photo was
	taken, but this field was reset to "n" (no) because the snow depth
	was 0.  The roughness photograph at this pit was not deleted,
	however.

916    Surface wetness reset to missing value:  Snow depth is 0.

	Measurement protocol was to record surface wetness only when snow
	depth was greater than 0.  In this case a recorded surface wetness
	was reset to missing because the snow depth was 0.

917    Canopy height reset to missing value:  Snow depth is 0.

        Canopy height field was introduced (in North Park only) during
        IOP2.  Measurement protocol was to record canopy height only when
        snow depth was greater than 0.  In this case a recorded canopy
        height was reset to missing because the snow depth was 0.

950    Warning: Shallow pit form used, but pit depth > 15 cm.

	Measurement protocol was to use the "shallow" pit form when the
	snow depth was less than 15 cm.

951    Warning: Deep pit form used, but pit depth < 15 cm.

	Measurement protocol was to use the "deep" pit form when the
	snow depth was more than 15 cm.

990    Warning: One or both UTM coordinates are missing.

	Pit coordinates are incomplete or missing.

991    Warning: Missing date and/or time field.

        Date and/or time field are missing.

999    No data collected for this pit.

        Data were not collected at this pit location, due to safety
        hazard, weather conditions, or lack of time.

3. Data Access and Tools

Snow pit data are available at ftp://sidads.colorado.edu/pub/DATASETS/CLP/data/ground_data/nsidc0176_snow_pits/.

4. Data Acquisition and Processing

For detailed information about snow pit data, please see the CLPX Snow Pit Measurements documentation.

5. References and Related Publications

Please see the References section of the CLPX Plan.

ESRI Shapefile Technical Description (http://www.esri.com/library/whitepapers/pdfs/shapefile.pdf)

ISA Snow Depth Transects and Related Measurements, Version 2.0

6. Document Information

Document Creation Date

15 August 2003

Document Revision Date

12 October 2005

Document URL

http://nsidc.org/data/docs/daac/nsidc0176_clpx.gd.html