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
telephone, electronic mail, or fax.

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