BOREAS HYD-04 Areal Snow Course Data

Summary

The BOREAS HYD-04 work was focused on collecting data during the winter
field campaign (FFC-W) to improve the understanding of winter processes
within the boreal forest. Knowledge of snow cover and its variability in
the boreal forest is fundamental if BOREAS is to achieve its goals of
understanding the processes and states involved in the exchange of
energy and water. The development and validation of remote sensing
algorithms will provide the means to extend the knowledge of these
processes and states from the local to the regional scale. A specific
thrust of the hydrology research is the development and validation of
snow cover algorithms from airborne passive microwave measurements.

Airborne remote sensing data (gamma, passive microwave) were acquired
along a series of flight lines established in the vicinity of the BOREAS
study areas. Ground snow surveys were conducted along selected sections
of these aircraft flight lines. These calibration segments were
typically 10-20 km in length, and ground data were collected at 1- to
2-km intervals. The data are provided in tabular American Standard Code
for Information Interchange (ASCII) files.

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

1.1 Data Set Identification

BOREAS HYD-04 Areal Snow Course Data

1.2 Data Set Introduction

These ground snow survey data were collected to calibrate gamma and
passive microwave remote sensing data that were acquired in the BOREAS
study areas.

These data were collected during the BOREAS Focused Field
Campaign-Winter (FFC-W) in 1994 and cover 10-20 km lengths with
measurements representing the snow conditions for 1- to 2-km intervals
along those lengths. This data set should be used in conjunction with
the HYD-06 Airborne Gamma Ray Soil Moisture Data since these 2 data sets
cover the same sites. Please consult the documentation for this HYD-06
data set for more information about the transects.

1.3 Objective/Purpose

These data were collected during the BOReal Ecosystem Atmosphere Study
(BOREAS) FFC-W, which took place during the period 02-18-Feb-1994. These
data were collected to provide detailed spatial snow depth and snow
water equivalent (SWE) measurements in the BOREAS study areas to
validate airborne remote sensing techniques and to serve as the basis in
algorithm development to determine SWE using passive microwave data.
These data will also provide background information for other BOREAS
hydrological and satellite remote sensing components.

1.4 Summary of Parameters

Flight line number

location (latitude/longitude)

average snow water

SWE

depth and density

number of samples

standard deviation of SWE and depth

general land cover characteristics

1.5 Discussion

Ground snow survey data were collected along preselected calibration
lines

of the airborne snow survey flight line network. Along each calibration
line,

snowpack information was obtained at a series of equally spaced
locations

along the line (e.g., 1 or 2 km). A concerted effort was made to locate

sampling points in vegetation of the type and approximate percentage
cover representative of the calibration flight line. Up to three SWE and
depth

measurements plus 15 additional snow depth measurements were taken at
each

sampling location.

Data were collected along 15 calibration lines in the Southern Study
Area (SSA), 3 lines in the Northern Study Area (NSA) and 5 lines along a
transect between the two study areas. Each calibration line was
subsequently subdivided into approximately equal length segments called
bins. Each bin represents an area of similar vegetation, determined by
detailed land cover analysis of the BOREAS land classification by
HYD-04, which was then provided to HYD-06 for processing the airborne
gamma data. All reference coordinates are taken from Global Positioning
System (GPS) North American Datum of 1983 (NAD83) sampling point
locations averaged to represent the approximate center of the
calibration line or bin.

1.6 Related Data Sets

BOREAS HYD-04 Standard Snow Course Data

BOREAS HYD-06 Aircraft Gamma Ray Soil Measurement Data

BOREAS HYD-06 Ground Measurements of Soil Moisture

BOREAS HYD-06 Moss/Humus Moisture Data

BOREAS HYD-03 Snow Measurements

2\. Investigator(s)

2.1 Investigator(s) Name and Title

Dr. Barry Goodison

Chief, Climate Processes and Earth Observation Division

Climate Research Branch

Anne Walker

Scientist

Climate Research Branch

2.2 Title of Investigation

Determination of snow cover variations in the boreal forest using
passive

microwave radiometry.

2.3 Contact Information

Contact 1

\-\-\-\-\-\-\-\-\-\-\-\--

John R. Metcalfe

Atmospheric Environment Service

Downsview, ON

Canada

\(416\) 739-4354

\(416\) 739-5700 (fax)

john.metcalfe@ec.gc.ca

Contact 2

\-\-\-\-\-\-\-\-\-\-\-\--

Dr. B.E. Goodison

Atmospheric Environment Service

Downsview, ON

Canada

\(416\) 739-4345

\(416\) 739-5700 (fax)

barry.goodison@ec.gc.ca

Contact 3

\-\-\-\-\-\-\-\-\-\-\-\--

Anne Walker

Atmospheric Environment Service

Downsview, ON

\(416\) 739-4357

\(416\) 739-5700 (fax)

anne.walker@ec.gc.ca

3\. Theory of Measurements

Snow sampling equipment consists of a graduated tube with a cutter fixed
to

its lower end to permit easy penetration of the snow and a spring
balance

(reading directly in water equivalent units) to weigh the tube and its

contents. The density of the snow is calculated by dividing the SWE by
the depth of the snow at the sample point. Additional snow depth
measurements were made with a graduated stick or ruler.

4\. Equipment

4.1 Sensor/Instrument Description

The large diameter Eastern Snow Conference (ESC)-30 metric snow sampler
with a cutter area of 30 cm^2^ was used to obtain SWE measurements. A
complete description of this sampler along with plans, specifications,
and an assessment of errors and accuracy can be found in Farnes et al.,
1982. The ESC-30 sampler is the current standard sampler used by the
Atmospheric Environment Service (AES) for shallow snowpack regions. The
following is a complete list of equipment supplied to the surveyors:

1 ESC-30 snow sampler, 1 spring balance for ESC-30, 1 cradle, 1
measuring

stick/ruler (cm), field book or snow survey form and pencil.

4.1.1 Collection Environment

These data were collected under snow cover conditions at various sites
in the SSA and NSA.

4.1.2 Source/Platform

Measurements were made at selected sites, predetermined from a fixed
point at the start of the calibration line. Individual points were
selected randomly in a circle extending approximately 50 m in from the
edge of the forest. Ground irregularities (e.g., boulders, logs) were
avoided.

4.1.3 Source/Platform Mission Objectives

The objective of collecting this data was to provide ground-based snow
measurements coincident with airborne microwave and gamma airborne
missions for algorithm development and validation.

4.1.4 Key Variables

Snow depth, density, water equivalent, land cover characteristic, and
snowpack structure.

4.1.5 Principles of Operation

The snow sampler is lowered vertically into the snowpack with a steady
thrust downward. A small amount of twisting aids in driving the tube and
cutting thin ice layers; however, considerable force and driving of the
sampler may be required to penetrate hard layers of ground ice.
Penetration to extract a soil plug helps to prevent the loss of the snow
core from the tube; a trace of soil or litter in the cutter indicates
that no loss has occurred. Observation of the length of the snow core
permits a quick assessment of whether a complete core is obtained; the
depth of snow is measured when the sampler is inserted in the snowpack.
The sample is weighed in the tube and the combined weight (in water
equivalent units) is read directly with the spring balance. The tare
weight of the tube is subtracted to obtain the SWE. The density of the
snow is determined by dividing the water equivalent by the depth of the
snow. A graduated meter stick is used in obtaining ancillary snow depth
measurements.

More detailed information on suggested snow survey procedures is
available in Snow survey and water supply forecasting (U.S. Soil
Conservation Service, 1972), Snow surveying (Atmospheric Environment
Service, 1973), and Guide to Hydrological Practices (World
Meteorological Organization, 1974).

4.1.6 Sensor/Instrument Measurement Geometry

The ESC snow sampler extracts a snow core with a surface area of 30
cm^2^.

4.1.7 Manufacturer of Sensor/Instrument

The ESC-30 snow sampler and spring balance are manufactured and
calibrated according to Atmospheric Environment Service (AES)
specifications. The ESC-30 snow sampler was made under contract for AES.
There are no commercial manufacturers of this instrument. Please see
specifications on how to make the snow tube in Farnes et al., 1982.

4.2 Calibration

The spring balance is used to weigh snow samples. The balance is held in
a free position, and the snow sampler tube containing the snow sample is
suspended from the balance in a special cradle. The inner and outer
tubes of the balance are made of anodized aluminum. The anchorages for
the spring in the outer and inner tubes are designed to permit free,
unrestricted flexing of the spring over its entire effective length. The
balance has a ring at the top for hanging the balance and a hook at the
other end from which the snow sampler cradle is hung. The inner tube has
a scale engraved into it, which reads from 0 at the bottom to 125 at the
top. The scale indicates the SWE in centimeters.

4.2.1 Specifications

Calibration is performed by the manufacturer using a set of known
weights to adjust the magnification of the spring. For more information,
see AES spring balance calibration procedure, February 1987, issue 2.

4.2.1.1 Tolerance

A balance must read within ±0.3 cm of the actual weight at all levels up
to 60.5 cm and ±0.4 cm at levels above 60.5 cm.

4.2.2 Frequency of Calibration

Spring balances are checked annually before snow surveys begin. A pail
and water (1 liter) can be used to check the accuracy of the balance.
First, use a pail of water to register a positive reading on the
balance, then add 1 liter of water to the pail. The difference between
the two scale readings should equal 37.8 ±0.3 cm.

4.2.3 Other Calibration Information

The spring balance should be checked from time to time during the
season. Consistent repeat readings (i.e., tare) should be observed, with
no indication of appreciable sticking of the spring in the balance. This
ensures that the balance is not giving a false reading because the
spring is not moving freely.

5\. Data Acquisition Methods

Procedures similar to those described in the data set identified as
Standard

Snow Surveys were used. However, 3 SWE and 15 additional depth
measurements had to be made at each sampling location. The individual
sampling points were randomly selected (not predetermined) and were
marked with a T-bar fence post.

6\. Observations

Observations include detailed snowpack statigraphy, including ground,
snow, snow surface temperatures, and snow grain type and size.

6.1 Data Notes

None given.

6.2 Field Notes

Copies of field notes are available from the primary contact.

7\. Data Description

7.1 Spatial Characteristics

7.1.1 Spatial Coverage

These data were collected at the two BOREAS study areas in coordination
with aircraft measurements made by the BOREAS HYD-06 team.. The two
study areas are located within a large area of interest covering over a
million square kilometers in the Canadian Provinces of Saskatchewan and
Manitoba. Each of the study areas is approximately 50 by 100 km.

The HYD-06 aircraft flew at an altitude of 150 m AGL and measured
natural terrestrial gamma radiation, on average, over an average path
10.7 km long and 305 m wide, or an areal extent of 3.3 km2. Water
content was collected at various points along the flight. The number and
timing of the flight lines flown each day were determined by the need
for ground calibration and on the basis of need for other studies
(priority was given where possible to obtaining measurements over flight
lines associated with ground tower sites) and the amount of flight hours
remaining for the aircraft before required maintenance.

These measurements were made within the NSA and SSA and along a transect
that is between these two study areas.

There is a reference file associated with the HYD-06 data that contains
information about the location of the various flight lines.

NSA Spatial Coverage (North American Datum 1983 (NAD83))

Longitude Latitude

\-\-\-\-\-\-\-\-- \-\-\-\-\-\--

Upper Left -98.82 56.247

Upper Right -97.24 56.081

Lower Right -97.49 55.377

Lower Left -99.05 55.54

SSA Spatial Coverage

Longitude Latitude

\-\-\-\-\-\-\-\-- \-\-\-\-\-\-\--

Upper Left -106.23 54.319

Upper Right -104.24 54.223

Lower Right -104.37 53.419

Lower Left -106.32 53.513

7.1.2 Spatial Coverage Map

Maps of the study sites are given in the following diagrams.

![](media/image1.png){width="5.0in" height="4.0in"}

![](media/image2.png){width="5.0in" height="4.0in"}

7.1.3 Spatial Resolution

These data are point source measurements at the locations indicated.

7.1.4 Projection

Not applicable.

7.1.5 Grid Description

Not applicable.

7.2 Temporal Characteristics

7.2.1 Temporal Coverage

These data were collected from 03-Feb-1994 to 10-Mar-1994.

7.2.2 Temporal Coverage Map

The list of sites and dates when the data were collected is too long to
list here. Most measurements took place between 04-FEB-1994 and
11-FEB-1994. Data for flight line BP212 was collected on 10-MAR-1994.

7.2.3 Temporal Resolution

Data were collected at a single point in time for the various sites.

7.3 Data Characteristics

Data characteristics are defined in the companion data definition file
(h04assd.def).

7.4 Sample Data Record

Sample data format shown in the companion data definition file
(h04assd.def).

8\. Data Organization

8.1 Data Granularity

All of the Areal Snow Course Data are contained in one dataset.

8.2 Data Format(s)

The data files contain numerical and character fields of varying length
separated by commas. The character fields are enclosed with a single
apostrophe marks. There are no spaces between the fields. Sample data
records are shown in the companion data definition files (h04assd.def).

9\. Data Manipulations

9.1 Formulae

9.1.1 Derivation Techniques and Algorithms

density = (swe/(depth\*10))\*1000

9.2 Data Processing Sequence

9.2.1 Processing Steps

None given.

9.2.2 Processing Changes

None.

9.3 Calculations

9.3.1 Special Corrections/Adjustments

None.

9.3.2 Calculated Variables

None.

9.4 Graphs and Plots

None.

10\. Errors

10.1 Sources of Error

Errors in the data collected by the snow survey teams may arise from
several

sources:

1\) Warm temperatures, which can cause snow to stick in the tube.

2\) Changes to scale precision caused by air temperature fluctuations.

3\) Scale readings by different observers or during windy conditions,
which can yield erratic scale readings.

10.2 Quality Assessment

The quality of the data collected by the survey teams is thought to
range

from good to excellent; generally it is considered to be excellent.

Generally, data quality is potentially lowest when the snowpack is

shallowest. No formal quality assurance is done; however, a coarse check

was made after the completion of the survey.

10.2.1 Data Validation by Source

The data were spot checked by BORIS to make sure that no conversion
errors occurred during loading.

10.2.2 Confidence Level/Accuracy Judgment

This data set represents the best estimate of snow depth and SWE by land
cover/vegetation type for the immediate vicinity of the snow course on
the date of the survey. Care should be exercised when extrapolating the
measurements in time and/or to a much larger geographic area.

10.2.3 Measurement Error for Parameters

Given by standard error for SWE and depth.

10.2.4 Additional Quality Assessments

None.

10.2.5 Data Verification by Data Center

The data set was reviewed to ensure that it represents the data that are
described.

11\. Notes

11.1 Limitations of the Data

This data set represents the best estimate of snow depth and SWE by land
cover/vegetation type for the immediate vicinity of the snow course on
the date of the survey. Care should be exercised when extrapolating the
measurements in time and/or to a much larger geographic area.

11.2 Known Problems with the Data

None given.

11.3 Usage Guidance

Care should be exercised when extrapolating the measurements in time
and/or to a much larger geographic area.

11.4 Other Relevant Information

None.

12\. Application of the Data Set

This data set can be used to develop and validate snow cover algorithms
from airborne passive microwave measurements or other remote sensing
techniques where SWE can be estimated.

13\. Future Modifications and Plans

None.

14\. Software

14.1 Software Description

None.

14.2 Software Access

None.

15\. Data Access

15.1 Contact Information

Ms. Beth Nelson

BOREAS Data Manager

NASA GSFC

Greenbelt, MD

\(301\) 286-4005

\(301\) 286-0239 (fax)

beth@ltpmail.gsfc.nasa.gov

15.2 Data Center Identification

See Section 15.1.

15.3 Procedures for Obtaining Data

Users may place requests by telephone, electronic mail, or fax.

15.4 Data Center Status/Plans

The BOREAS HYD-04 areal snow course data are available from the Earth
Observing System Data and Information System (EOSDIS) Oak Ridge National
Laboratory (ORNL) Distributed Active Archive Center (DAAC).

The BOREAS contact at ORNL is:

ORNL DAAC User Services

Oak Ridge National Laboratory

\(865\) 241-3952

ornldaac@ornl.gov

ornl@eos.nasa.gov

16\. Output Products and Availability

16.1 Tape Products

None.

16.2 Film Products

None.

16.3 Other Products

The data and documentation are available as ASCII files.

17\. References

17.1 Platform/Sensor/Instrument/Data Processing Documentation

Atmospheric Environment Service. 1973. Snow surveying. 2^nd^ Ed.
Environ. Can., Downsview. Ont.

Farnes, P.E., N.R. Peterson, B.E. Goodison and R.P. Richards. 1982.
Metrication

of Manual Snow Sampling Equipment by Western Snow Conference Metrication

Committee. 39th Annual Proceedings of the Eastern Snow Conference, Reno,
NV, Apr. 19-23, 1982, pp. 120-132.

Goodison, B.E., J.E. Glynn, K.D. Harvey, and J.E. Slater, 1987. Snow
Surveying in Canada: A Perspective. Can. Wat. Res. Jr., Vol. 12, 2, pp.
27-42.

U.S. Soil Conservation Service. 1972. Snow survey and water supply
forecasting. Section 22, SCS Nat. Eng. Handb., U.S. Dept. Agric.,
Washington, DC.

World Meteorological Organization. 1974. Guide to hydrological
practices. 3^rd^ Ed. Ch. 2, Instruments and Methods of Observation. WMO
No.168, World Meteorological Organization, Geneva, pp. 2.1-2.90.

17.2 Journal Articles and Study Reports

Goita, K., A.E. Walker, B.E. Goodison, and A.T.C. Chang. 1997.
Estimation of Snow Water Equivalent in the Boreal Forest using Passive
Microwave Data, Proc. (CD-ROM) GERí97 (Geomatics in the Era of
Radarsat). Ottawa, Canada, May 25-30, 1997.

Sellers, P. and F. Hall. 1994. Boreal Ecosystem-Atmosphere Study:
Experiment Plan. Version 1994-3.0, NASA BOREAS Report (EXPLAN 94).

Sellers, P. and F. Hall. 1996. Boreal Ecosystem-Atmosphere Study:
Experiment Plan. Version 1996-2.0, NASA BOREAS Report (EXPLAN 96).

Sellers, P. and F. Hall. 1997. BOREAS Overview Paper. JGR Special Issue
(in press).

Sellers, P., F. Hall, and K.F. Huemmrich. 1996. Boreal
Ecosystem-Atmosphere Study: 1994 Operations. NASA BOREAS Report (OPS DOC
94).

Sellers, P., F. Hall, and K.F. Huemmrich. 1997. Boreal
Ecosystem-Atmosphere Study: 1996 Operations. NASA BOREAS Report (OPS DOC
96).

Sellers, P., F. Hall, H. Margolis, B. Kelly, D. Baldocchi, G. den
Hartog, J. Cihlar, M.G. Ryan, B. Goodison, P. Crill, K.J. Ranson, D.
Lettenmaier, and D.E. Wickland. 1995. The boreal ecosystem-atmosphere
study (BOREAS): an overview and early results from the 1994 field year.
Bulletin of the American Meteorological Society. 76(9):1549-1577.

Walker, A.E., B.E. Goodison, and J.R. Metcalfe. 1995. Investigation of
Boreal

Forest Snow Cover Variations During the BOREAS 1994 Winter Campaign.
17th

Canadian Symposium on Remote Sensing, Saskatoon, Saskatchewan, June
13-15,

1995\.

Walker, A.E., B.E. Goodison, and J.R. Metcalfe. 1995. Investigation of
Boreal

Forest Snow Cover Variations During the BOREAS 1994 Winter Campaign.
29th

Canadian Meteorological and Oceanographic Society Congress, Kelowna,
British

Columbia, May 30-June 2, 1995.

17.3 Archive/DBMS Usage Documentation

None.

18\. Glossary of Terms

None.

19\. List of Acronyms

AES - Atmospheric Environment Service

ASCII - American Standard Code for Information Interchange

BOREAS - BOReal Ecosystem-Atmosphere Study

BORIS - BOREAS Information System

CGR - Certified by Group

CPI - Certified by Principal Investigator

CPI-??? - CPI but questionable

DAAC - Distributed Active Archive Center

EOS - Earth Observing System

EOSDIS - EOS Data and Information System

ESC - Eastern Snow Conference

FFC-W - Focused Field Campaign - Winter

GSFC - Goddard Space Flight Center

HYD - Hydrology

NASA - National Aeronautics and Space Administration

NSA - Northern Study Area

ORNL - Oak Ridge National Laboratory

PANP - Prince Albert National Park

PI - Principal Investigator

PRE - Preliminary

SSA - Southern Study Area

SWE - Snow Water Equivalent

URL - Uniform Resource Locator

20\. Document Information

20.1 Document Revision Date

Written: 01-May-1995

Last Revised: 06-Jul-1998

20.2 Document Review Date

BORIS Review: 26-Feb-1998

Science Review: 13-Jan-1998

20.3 Document ID

20.4 Citation

The areal snow survey data were collected by personnel with the Climate

Research Branch, AES, with assistance from personnel from the University
of

Waterloo, Dept. of Civil Engineering, NASA GSFC, and the Norwegian
Institute of

Technology.

20.5 Document Curator

20.6 Document URL

Keywords

\-\-\-\-\-\-\-\--

SNOW DENSITY

SNOW WATER EQUIVALENT