BOREAS HYD-05 Bear Trap Creek and Namekus Lake Winter Surface Flux Data
Summary
The BOREAS HYD-05 team collected tower flux, surface meteorological, and surface 
temperature data on a frozen lake (Namekus Lake) and in a mature jack pine forest 
in the Beartrap Creek watershed.  Both sites were located in the BOREAS SSA.  The 
objective of this study was to characterize the winter energy and water vapor 
fluxes, as well as related properties (such as snow density, depth, temperature, 
and melt) for forested and nonforested areas of the boreal forest.  Data were 
collected on Namekus Lake in the winters of 1994 and 1996, and at Beartrap Creek 
in the winter of 1994 only.  The data are available in tabular 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-05 Winter Surface Fluxes 
1.2 Data Set Introduction
Surface flux, meteorological, and temperature data were collected on the frozen 
surface of Namekus Lake and in a mature, slightly open, jack pine stand (Pinus 
banksia) in the Beartrap Creek catchment.  Both sites are in the Prince Albert 
National Park (PANP) in the BOReal Ecosystem-Atmosphere Study (BOREAS) Southern 
Study Area (SSA).  Data were collected on Namekus Lake in the winters of 1994 and 
1996 and at Beartrap Creek in the winter of 1994 only.
1.3 Objective/Purpose
The objective of this study was to characterize the winter energy and water 
vapor fluxes, as well as related properties (such as snow density, depth, 
temperature, and melt) for forested and nonforested areas of the boreal 
forest. 
1.4 Summary of Parameters and Variables
Latent heat flux, sensible heat flux, net radiation, humidity, wind speed and 
direction, air temperature, incident and reflected shortwave radiation, and 
surface temperature data were collected.
1.5 Discussion
A comparison of a surface meteorology and energy balance of a snow-covered lake 
and an adjacent forest area was made.  There were small, but measurable, 
contrasts in the temperature and wind speed measured over the lake and forest 
(the lake was cooler and windier), but it is the comparison of the energy balance 
of the forest and the open snow surface that is dramatic: the mean net radiation 
flux was into the forest canopy but out of the snow-covered lake.  Similarly, 
when the forest canopy was clear of snow, the sensible heat flux was of different 
sign (and magnitude) over the forest and lake.  When the forest canopy was snow-
covered the partition of the sensible and latent heat fluxes was different again, 
exhibiting a large upward latent heat flux and a compensating downward sensible 
heat flux.
1.6 Related Data Sets
Tower flux measurements made in the winter at other sites:
BOREAS TF-01 SSA OA Tower Flux, Meteorological, and Soil Temperature Data
BOREAS TF-03 NSA OBS Tower Flux, Meteorological, and Soil Temperature Data
BOREAS TF-09 SSA OBS Tower Flux, Meteorological, and Soil Temperature Data
Other measurements made at the HYD-05 sites:
BOREAS HYD-03 Snow Measurements
2. Investigator(s)
2.1 Investigator(s) Name and Title
Richard Harding
Institute of Hydrology
2.2 Title of Investigation
The Regional Representation of the Energy and Moisture Fluxes from Snow 
Covered Areas in the BOREAS Experiment
2.3 Contact Information
Contact 1    
---------
Richard Harding
Institute of Hydrology
Crowmarsh Gifford
Wallingford Oxfordshire
United Kingdom
44 1491 838800
44 1491 832256 (fax)
R.Harding@unixa.nerc-wallingford.ac.uk
Contact 2 
-------------
K. Fred Huemmrich
University of Maryland
NASA GSFC 
Greenbelt, MD
(301) 286-4862
(301) 286-0239 (fax)
Karl.Huemmrich@gsfc.nasa.gov
3. Theory of Measurements
This study collected data to contrast the winter energy and water vapor fluxes 
for forested and nonforested areas of the boreal forest.  The long, cold winter 
characteristic of the boreal forest causes cessation of growth for 5 to 7 months 
of the year and is the most distinguishing feature of this biome.  The components 
of the energy balance, which determine the net energy supply to the canopy and 
the snow surface, are small during this winter period - with direct effects on 
biological activity.  Most of the components of the energy balance: the radiation 
flux (solar and thermal), sensible heat flux (turbulent transfer of heat from the 
surface to the atmosphere), latent heat flux (evaporative cooling or warming upon 
condensation), and to a lesser degree the soil heat flux, are strongly influenced 
by the presence and depth of snow cover and its interaction with vegetation.  
Snow reflects most incident solar radiation and hence dramatically reduces the 
net radiative energy input.  However, when the snow covers a forest canopy, the 
multiple reflections within the canopy scatter rather than reflect the majority 
of incident radiation, and the albedo remains low (Harding and Pomeroy, 1996; van 
de Hulst, 1957; Oke, 1978).
4. Equipment
4.1 Sensor/Instrument Description
4.1.1 Collection Environment
There were two sites in this study.  The first site was a mature, slightly open, 
jack pine stand (Pinus banksia) in the Beartrap Creek catchment.  The fetch was 
level and reasonably uniform for at least 100 m.   The pine canopy was 16-22 m in 
height with a sparse understory of deciduous bushes.  The winter "leaf" (branch 
and needle) area index of this stand was 2.2, and the canopy cover of sky was 82% 
measured with a LI-COR LAI-2000 Canopy Density meter (Gower and Norman, 1991).  
The second site was on the snow-covered frozen surface of Namekus Lake, 10 km 
southeast of the jack pine stand.  The surface was quite smooth (snow over ice), 
and the fetch exceeded 700 m.  Data were collected at both sites during winter 
periods, experiencing temperatures as low as -37 C on the lake to a high of 18 
C over the forest.
4.1.2 Source/Platform
The Beartrap Creek site was equipped with a 26-m meteorological tower from which 
measurements were taken of shortwave radiation (downward and reflected) and net 
all-wave radiation above and below the canopy, along with vertical profiles of 
temperature, humidity, snow particle flux, and wind speed through the canopy.  A 
"Hydra" eddy correlation system was also operated from the top of the tower for 
direct measurement of sensible and latent heat fluxes (Shuttleworth et al., 
1988).  Hydra was developed at the Institute of Hydrology.  It consists of a 
vertical component sonic anemometer, a fine wire thermocouple thermometer, an 
infrared absorption hydrometer, and a fast response cup anemometer.  A second 
eddy correlation system measuring only sensible heat flux was operated from the 
tower.  This consisted of a "solent" sonic anemometer (Gill Instruments Ltd., 
Lymington, U.K.), a fine wire thermocouple, and a Campbell Scientific CR21 with 
software similar to that described by Shuttleworth et al. (1988).
The net all-wave radiation above the canopy was measured with two instruments, 
both on short (~2 m) booms at the top of the tower; a Middleton radiometer and a 
Radiation Energy Balance Systems (REBS), Seattle, Washington) Q*5.  Below the 
canopy, shortwave and net all-wave radiation were measured with "Delta 7" tube 
radiometers (Delta-T Devices Ltd., Cambridge, U.K.).  These tubes (almost 1 meter 
in length) average the speckled light found beneath the canopy (Szeicz et al,. 
1964).
The Namekus Lake site was equipped with a 3-m mast with instruments to measure 
the two shortwave components of the radiation balance, the all-wave net 
radiation, temperature, humidity, snow particle flux, and wind speed (at 1, 2, 
and 3 m) above the snow surface.  A second Hydra was operated to provide fluxes 
of heat and water vapor.
Nipher-shielded snow gauges under the forest canopy and in a nearby open area 
provided weekly snowfall and snow interception.  Weekly snow surveys, both 
underneath the forest canopy and on the lake, were undertaken to give average 
snow depth and the water equivalent of the pack.
4.1.3 Source/Platform Mission Objectives
Towers were established to support the measurement of tower flux, surface 
meteorological, and surface temperature data on a frozen lake (Namekus Lake) and 
in a mature jack pine forest (Beartrap Creek).
4.1.4 Key Variables
Latent heat flux, sensible heat flux, net radiation, humidity, wind speed and 
direction, air temperature, incident and reflected shortwave radiation, and 
surface temperature data were collected.
4.1.5 Principles of Operation
The Hydra, based on the eddy correlation technique, consists of sensors and real-
time and offline computers.  It is a complete instrumentation system, designed 
specifically to provide routine measurements of the surface energy fluxes with 
minimum supervision.
4.1.6 Sensor/Instrument Measurement Geometry
Beartrap Creek site: 
At the top of a 26-m meteorological tower: Hydra eddy correlation system and a 
Solent sonic anemometer.
On short (~2 m) booms at the top of the tower: a Middleton radiometer and a REBS 
Q*5.
Below the canopy: Delta 7 tube radiometers.
Namekus Lake site: 
A 3-m mast with a Hydra eddy correlation system and instruments to measure the 
two shortwave components of the radiation balance, the all-wave net radiation, 
temperature, humidity, snow particle flux, and wind speed (at 1, 2, and 3 m) 
above the snow surface.
The Hydra has to be set up so that the sonic anemometer is at right angles to the 
local stream lines of the flow. 
Nipher-shielded snow gauges under the forest canopy and in a nearby open area.
4.1.7 Manufacturer of Sensor/Instrument
Hydra eddy correlation system:
Developed at the Institute of Hydrology
Hydra consists of a vertical component sonic anemometer, a fine wire thermocouple 
thermometer, an infrared absorption hydrometer, and a fast response cup 
anemometer.
Solent sonic anemometer: 
Gill Instruments Limited 
Solent House 
Cannon Street 
Lymington, 
Hampshire  SO41 9BR 
UK 
Campbell Scientific CR21:
Campbell Scientific 
P.O. Box 551 
Logan, UT 84321 
USA 
REBS Q*5:
Radiation Energy Balance Systems
P.O. Box 15512 
Seattle, WA 98115-0512 
USA 
Delta 7 tube radiometers:
Delta-T Devices Ltd.
128 Low Rd, Burwell,
Cambs CB5 .0EJ
UK
4.2 Calibration
4.2.1 Specifications
A constant check of the Hydra's performance is made on a 24-hour basis by 
checking that the sum of sensible and latent heat fluxes is equivalent to the 
available energy for this same period. +/-10% is considered good, although +/-
20% is quite common, especially when weather conditions are changeable.  If 
errors become consistent or if a failure occurs, a spare set of sensors and 
electronics is carried with each Hydra, which is designed to accept changeover 
in the field easily.
4.2.1.1 Tolerance
Not known.
4.2.2 Frequency of Calibration
The Hydra is calibrated typically once a year if it is not overseas for longer 
than this.   
4.2.3 Other Calibration Information
Not known.
5. Data Acquisition Methods
None given.
6. Observations
6.1 Data Notes
None given.
6.2 Field Notes
None given.
7. Data Description
7.1 Spatial Characteristics
7.1.1 Spatial Coverage
All data were collected at two sites in PANP in the BOREAS SSA.  The North 
American Datum 1983 (NAD83) coordinates of these sites were:
Site                Latitude          Longitude
--------------      -----------       ------------
Beartrap Creek      53.84779 N       106.17090 W
Namekus Lake        53.83101 N       106.04127 W
7.1.2 Spatial Coverage Map
Not available.
7.1.3 Spatial Resolution
The data represent point source measurements taken at the given locations. The 
location and size of the footprint from which the measurements were made varied 
with ambient meteorological conditions.  At the Beartrap Creek site, the fetch 
was level and reasonably uniform for at least 100 m.  At the Namekus Lake site 
the surface was quite smooth (snow over ice) during data collection, and the 
fetch exceeded 700 m.
7.1.4 Projection
Not applicable.
7.1.5 Grid Description
Not applicable.
7.2 Temporal Characteristics
7.2.1 Temporal Coverage
For the Beartrap Creek site, measurements are available from 03-Feb to 17-Apr-
1994.  For the Namekus Lake site, measurements are available from 10-Feb to 28-
Mar-1994 and 17-Mar to 07-Apr-1996.
7.2.2 Temporal Coverage Map
All data were collected at the Beartrap Creek and Namekus Lake sites.
7.2.3 Temporal Resolution
Data values are reported hourly.
7.3 Data Characteristics
Data characteristics are defined in the companion data definition file 
(h5flxd.def).
7.4 Sample Data Record
Sample data format shown in the companion data definition file (h5flxd.def).
8. Data Organization
8.1 Data Granularity
The Bear Trap Creek and Namekus Lake Winter Surface Flux Data are contained in 
separate datasets.
8.2 Data Format
The data files contain numerical and character fields of varying length 
separated by commas.  The character fields are enclosed with single apostrophe 
marks.  There are no spaces between the fields. Sample data records are shown 
in the companion data definition file (h5flxd.def).
9. Data Manipulations
9.1 Formulae
See Shuttleworth et al. (1988) for a description of formulas used in the Hydra 
data processing.
9.1.1 Derivation Techniques and Algorithms
None given.
9.2 Data Processing Sequence
9.2.1 Processing Steps
See Shuttleworth et al. (1988) for a description of the Hydra data processing.
BORIS staff processed these data by:
1) Reviewing the initial data files and loading them online for BOREAS team 
access.
2) Designing relational database tables to inventory and store the data.
3) Loading the data into the relational database tables.
4) Working with the team to document the dataset.
5) Extracting the data into logical files.
9.2.2 Processing Changes
None.
9.3 Calculations
9.3.1 Special Corrections/Adjustments
None.
9.3.2 Calculated Variables
None given.
9.4 Graphs and Plots
None.
10. Errors
10.1 Sources of Error
Factors contributing to instrument errors include signal-to-noise ratio, height 
of the instrument, and sensor separation.  Non-steady conditions and surface 
inhomogeneities are sources of natural variability.
10.2 Quality Assessment
At the Namekus Lake site, the sum of the turbulent fluxes agrees reasonably with 
the input net radiation.  
At the Beartrap Creek site, the net radiation was measured by two completely 
separate systems, which agreed to within 10 W m-2, and the sensible heat fluxes 
were measured by two systems, and again the agreement was within a few watts per 
square meter.  Finally, measurement of the latent heat flux using eddy 
correlation is strongly supported by measurements from the weighted tree, which 
gave a continuous output of the weight of the snow on the forest canopy (the 
weighted tree data were not submitted to BORIS, contact the investigator for 
these data).
10.2.1 Data Validation by Source
Over the Namekus Lake, the sum of the turbulent fluxes agrees reasonably with the 
input net radiation (particularly considering the small size of the fluxes).  
Unfortunately, neither snowmelt nor ground (ice) heat fluxes were measured at 
this site; but the energy closure, neglecting these, suggests they were small.  
However, there appears to be an imbalance between the sensible and latent heat 
fluxes and the radiation input in the forest; the energy from net radiation and 
downward sensible heat flux could not provide sufficient energy to supply the 
high observed evaporation.  Measurements of ground heat flux are typically  2 W 
m-2 and so could not provide this energy.  It seems unlikely that the flux 
measurements were seriously in error: the net radiation was measured by two 
completely separate systems, which agreed to within 10 W m-2.  The sensible heat 
fluxes were again measured by two systems, and again the agreement was within a 
few watts per square meter.  Finally, measurement of the latent heat flux using 
eddy correlation is strongly supported by measurements from the weighted tree.  
It is possible that there was some strong horizontal advection at this site (with 
the localized radiation measurements being unrepresentative of the "footprint" of 
the measurements of the turbulent fluxes), or there is also the possibility of 
some large change of heat storage within the trunk space.
10.2.2 Confidence Level/Accuracy Judgment
None given.
10.2.3 Measurement Error for Parameters
None given.
10.2.4 Additional Quality Assessments
None given.
10.2.5 Data Verification by Data Center
Data were examined to check for spikes, values that are four standard deviations 
from the mean, long periods of constant values, and missing data.
11. Notes
11.1 Limitations of the Data
These data were collected while the ground was snow covered.
11.2 Known Problems with the Data
There appears to be an imbalance between the sensible and latent heat fluxes and 
the radiation input in the forest at the Beartrap Creek site; the energy from net 
radiation and downward sensible heat flux could not provide sufficient energy to 
supply the high observed evaporation.  Measurements of ground heat flux are 
typically 2 W m-2 and so could not provide this energy.  It is possible that 
there was some strong horizontal advection at this site (with the localized 
radiation measurements being unrepresentative of the "footprint" of the 
measurements of the turbulent fluxes), or there is also the possibility of some 
large change of heat storage within the trunk space.  This imbalance obviously 
requires further study.
11.3 Usage Guidance
None given.
11.4 Other Relevant Information
None given.
12. Application of the Data Set
This data set is useful for studying the winter energy and water balance of both 
open and forested sites.
13. Future Modifications and Plans
None given.
14. Software
14.1 Software Description
None given.
14.2 Software Access
None given.
15.   Data Access
15.1  Contact for Data Center/Data Access Information
These BOREAS data are available from the Earth Observing System Data and 
Information System (EOS-DIS) 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
15.2  Procedures for Obtaining Data
BOREAS data may be obtained through the ORNL DAAC World Wide Web site at 
http://www-eosdis.ornl.gov/ or users may place requests for data by fax, 
telephone, or electronic mail.
15.3  Output Products and Availability
Requested data can be provided electronically on the ORNL DAAC's anonymous FTP 
site or on various media including, CD-ROMs, 8-MM tapes, or diskettes.
The complete set of BOREAS data CD-ROMs, entitled "Collected Data of the Boreal 
Ecosystem-Atmosphere Study", edited by Newcomer, J., et al., NASA, 1999, are also 
available.
16. Output Products and Availability
16.1 Tape Products
None.
16.2 Film Products
None.
16.3 Other Products
The data are available as tabular American Standard Code for Information 
Interchange (ASCII) text files.
17. References
17.1 Platform/Sensor/Instrument/Data Processing Documentation
None.
17.2 Journal Articles and Study Reports
Gower, S.T., and J.M. Norman. 1991. Rapid estimation of leaf area index in 
conifer and broad-leaf plantations. Ecology. 72: 1896-1900.
Harding, R.J., and J.W. Pomeroy. 1996. The energy balance of the winter boreal 
landscape. Journal of Climate. 9(11): 2778-2787.
Oke, T.R. 1978. Boundary Layer Climates. Methuen and Sons, pp. 110-112.
Pomeroy, J.W., and K. Dion. 1996. Winter radiation extinction and reflection in a 
boreal pine canopy: measurements and modeling. Hydrol. Process. 10(12): 1591-
1608.
Sellers, P. and F. Hall. 1994. Boreal Ecosystem-Atmosphere Study: Experiment 
Plan. Version 1994-3.0, NASA BOREAS Report (EXPLAN 94). 
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. 
Sellers, P., F. Hall, and K.F. Huemmrich. 1996. Boreal Ecosystem-Atmosphere 
Study: 1994 Operations. NASA BOREAS Report (OPS DOC 94). 
Sellers, P. and F. Hall. 1996. Boreal Ecosystem-Atmosphere Study: Experiment 
Plan. Version 1996-2.0, NASA BOREAS Report (EXPLAN 96).
Sellers, P., F. Hall, and K.F. Huemmrich. 1997. Boreal Ecosystem-Atmosphere 
Study: 1996 Operations. NASA BOREAS Report (OPS DOC 96).
 
Sellers, P.J., F.G. Hall, R.D. Kelly, A. Black, D. Baldocchi, J. Berry, M. Ryan, 
K.J. Ranson, P.M. Crill, D.P. Lettenmaier, H. Margolis, J. Cihlar, J. Newcomer, 
D. Fitzjarrald, P.G. Jarvis, S.T. Gower, D. Halliwell, D. Williams, B. Goodison, 
D.E. Wickland, and F.E. Guertin. 1997. BOREAS in 1997: Experiment overview, 
scientific results, and future directions. Journal of Geophysical Research 
102(D24):28731-28769.
Shuttleworth, W.J., J.H. C. Gash, C.R. Lloyd, D.D. McNeil, C.J. Moore, and J.S. 
Wallace. 1988. An integrated micrometeorological system for evaporation 
measurement.  Agric. Meteor. 43: 295-317.
Szeicz, G., J.L. Monteith, and J. dos Santos. 1964. A tube solimeter to measure 
radiation among plants. J. Appl. Ecol. 1: 169-174.
Van de Hulst, H.C. 1957. Light Scattering by Small Particles. Wiley and Sons, 470 
pp.
17.3 Archive/DBMS Usage Documentation
None.
18. Glossary of Terms
None.
19. List of Acronyms
    ASCII   - American Standard Code for Information Interchange
    BOREAS  - BOReal Ecosystem-Atmosphere Study
    BORIS   - BOREAS Information System
    DAAC    - Distributed Active Archive Center
    EOS     - Earth Observing System
    EOSDIS  - EOS Data and Information System
    GSFC    - Goddard Space Flight Center
    HYD     - Hydrology
    NAD83   - North American Datum of 1983
    NASA    - National Aeronautics and Space Administration
    NSA     - Northern Study Area
    OBS     - Old Black Spruce
    ORNL    - Oak Ridge National Laboratory
    PANP    - Prince Albert National Park
    SSA     - Southern Study Area
    TF      - Tower Flux
    URL     - Uniform Resource Locator
20. Document Information
20.1 Document Revision Date
     Written: 13-Jul-1998
     Revised: 14-Sep-1998
20.2 Document Review Date(s)
     BORIS Review: 15-Jul-1998
     Science Review: 17-Aug-1998
20.3 Document ID
20.4 Citation
Data were collected by R.J. Harding.  Please cite the following article when 
using these data:  
Harding, R.J., and J.W. Pomeroy. 1996. The energy balance of the winter boreal 
landscape. Journal of Climate. 9(11): 2778-2787.
20.5 Document Curator
20.6 Document URL
Keywords
TOWER FLUX
METEOROLOGY
SNOW
WINTER
SENSIBLE HEAT FLUX
LATENT HEAT FLUX
NET RADIATION
AIR TEMPERATURE
WIND SPEED
SURFACE TEMPERATURE
HYD05_Flux.doc
09/14/98