NASA/TMm2000-209891, Vol. 200

Technical Report Series on the

Boreal Ecosystem-Atmosphere Study (BOREAS)

Forrest G. Hall and Karl Huemmrich, Editors

Volume 200

BOREAS TF-5 SSA-OJP

Tower Flux and Meteorological

Data

Dennis Baldocchi and Christoph Vogel

National Oceanic and Atmospheric Administration/ATDD

Oakridge, Tennessee

National Aeronautics and

Space Administration

Goddard Space Flight Center

Greenbelt, Maryland 20771

October 2000

https://ntrs.nasa.gov/search.jsp?R=20010022587 2018-05-14T19:22:03+00:00Z
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NASA/TMm2000-209891, Vol. 200

Technical Report Series on the

Boreal Ecosystem-Atmosphere Study (BOREAS)

Forrest G. Hall and Karl Huemmrich, Editors

Volume 200

BOREAS TF-5 SSA-OJP

Tower Flux and Meteorological

Data

Dennis Baldocchi and Christoph Vogel

National Oceanic and Atmospheric Administration/ATDD

Oakridge, Tennessee

National Aeronautics and

Space Administration

Goddard Space Flight Center

Greenbelt, Maryland 20771

October 2000
NASA Center for AeroSpace Information

7121 Standard Drive

Hanover, MD 21076-1320

Price Code: A17

Available from:

National Technical Information Service

5285 Port Royal Road

Springfield, VA 22161

Price Code: A10
BOREAS TF-5 SSA-OJP Tower Flux and Meteorological Data

Dennis Baldocchi, Christoph Vogel

Summary

The BOREAS TF-5 team collected tower flux data at the BOREAS SSA-OJP site through the growing

season of 1994. 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 TF-05 SSA-OJP Tower Flux and Meteorological Data

1.2 Data Set Introduction

Eddy correlation flux measurements of sensible heat, latent heat, and CO2 fluxes were made above

and under the canopy of the BOReal Ecosystem-Atmosphere Study (BOREAS) Southern Study Area

(SSA) Old Jack Pine (OJP) site.

1.3 Objective/Purpose

The objective was to measure and model air-surface exchange rates of water vapor, sensible heat,

and CO2 over and under a boreal forest and to study the abiotic and biotic factors that control the fluxes

of scalars in this landscape. Scalar flux densities were measured with tower-mounted measurement

systems. Tower-mounted flux measurement systems were installed above and below an old jack pine

forest canopy, which allowed investigation of the relative roles of vegetation and the forest floor on the

net canopy exchange of mass and energy. The tower-mounted flux measurement system was also used

to study temporal patterns (diurnal and seasonal) of mass and energy exchange at a point in the

landscape.

Page 1
1.4 Summary of Parameters

Key measured flux variables were net radiation, Photosynthetic Photon Flux Density (PPFD),

latent heat, sensible heat, soil heat, and CO2 flux densities above and below the canopy. Key measured

meteorological variables included wind speed, wind direction, air temperature, relative humidity, soil

temperature, CO2 concentration, and ozone concentration.

1.5 Discussion

Eddy flux densities of CO2, water vapor, and sensible heat and turbulence statistics were measured

above and below the OJP (Pinus banksiana) site near Nipawin (53.92 °N, 104.69 °W), Saskatchewan,

Canada. The site was relatively level and the forest stand was horizontally homogeneous throughout

the area deemed as the flux footprint, a region extending over 1 kin upwind.

One eddy flux measurement system was mounted at 20 m above the ground. This system was

about 5 to 10 m above the canopy and was mounted on the double scaffold tower p.ro.vided by the

BOREAS project. The sensors on a boom extended 3 m upwind of the tower, to minimize flow

distortion. The azimuth angle of the boom was altered to place the instrument array into the wind. The

subcanopy flux system was mounted 2 m above the ground on a portable telescoping tower, supplied

by National Oceanic and Atmospheric Administration/Atmospheric Turbulence and Diffusion Division

(NOAA/ATDD). This lower tower was placed 30 to 50 m away from the base of the main tower to

avoid interference from local foot traffic. This dual flux measurement method has been successfully

developed and used in a deciduous forest (Verma et al., 1986; Baldocchi et al., 1987; Baldocchi and

Meyers, 1991). By analogy, the investigators feel that the dual measurement approach can be used

with confidence above and below the jack pine stand.

The eddy flux densities were determined by calculating the covariance between vertical velocity and

scalar fluctuations (see Baldocchi et al., 1988). Wind velocity and virtual temperature fluctuations were

measured with identical 3-D sonic anemometers. Experience has shown that it is prudent to use 3-D

sonic anemometers in forest meteorology applications. When deploying an anemometer over a forest,

it is nearly impossible to physically align the vertical velocity sensor normal to the mean wind

streamlines; sensor orientation problems typically arise because of sloping terrain and the practice of

extending a long boom upwind from a tower. The use of a 3-D anemometer allows numerical

coordinate rotations to be made to align the vertical velocity measurement normal to the mean wind

streamlines. CO2 and water vapor fluctuations were measured with an open-path, infrared absorption

gas analyzer, developed at NOAA/ATDD (Auble and Meyers, 1992).

Fast-response meteorology data were digitized, processed, and stored using a

microcomputer-controlled system and in-house software. Digitization of sensor signals was performed

with hardware on the sonic anemometer. Sensor data were output at 10 Hz. Spectra and cospectra

computations showed that these sampling rates were adequate for measuring fluxes above and below

forest canopies (Baldocchi and Meyers, 1991; Amiro, 1990). Scalar fluctuations were computed,

real-time, using a running mean removal method (McMillen, 1988). Analytical and numerical tests

showed the recursive filter time constant of 400 s yielded fluxes similar to those computed with the

conventional Reynolds averaging approach. Mass and energy flux covariances were stored at half-hour

intervals on high-capacity Bernoulli removable disk media. Instantaneous data were recorded

periodically.

Proper interpretation of experimental results and model evaluation requires detailed ancillary

measurements of many environmental variables. Energy balance components that were measured

include the net radiation balance, soil heat flux, and canopy heat storage.

1.6 Related Data Sets

BOREAS TF-04 SSA-YJP Tower Flux, Meteorological, and Canopy Condition Data

BOREAS

BOREAS

BOREAS

BOREAS

BOREAS

BOREAS

BOREAS

TF-08 NSA-OJP Tower Flux Data

TF-09 SSA-OBS Tower Flux, Meteorological, and Soil Temperature Data

TF- 11 SSA-Fen Tower Flux and Meteorological Data

AFM-07 SRC Surface Meteorological and Radiation Data

TE-06 Allometry Data

TGB-10 Oxidant Concentration Data over the SSA

TGB- 10 Oxidant Flux Data over the SSA

Page 2
2. Investigator(s)

2.1 Investigator(s) Name and Title

Dr. Dennis Baldocchi and Dr. Christoph Vogel

NOAA/ATDD

2.2 Title of Investigation

Experimental and Modeling Studies of Water Vapor, Sensible Heat, and CO: Exchange Over and

Under a Boreal Forest

2.3 Contact Information

Contact 1:

Dennis Baldocchi

NOAA/ATDD

P.O. Box 2456

Oak Ridge, TN 37831

(423) 576-1243

(423) 576-1327 (fax)

baldocchi@ atdd.noaa.gov

Contact 2:

Christoph Vogel

NOAA/ATDD

P.O. Box 2456

Oak Ridge, TN 37831

(423) 576-1243

(423) 576-1327 (fax)

Contact 3:

Karl F. Huemmrich

University of Maryland

NASA GSFC

Code 923

Greenbelt, MD 20771

(301) 286-4862

(301) 286-0239 (fax)

Karl.Huemmrich@gsfc.nasa.gov

3. Theory of Measurements

Micrometeorological Measurement Theory:

Micrometeorological methods allow one to measure short-term flux densities (moles per unit area

and time) of scalar compounds to and from forest ecosystems. The equation describing the

conservation of mass provides the basic framework for applying micrometeorological methods to

measure the vertical flux density of S (F) between the surface and the atmosphere. The conservation

equation describes the factors that control the time rate of change of a scalar mixing ratio in a controlled

volume. To grasp an understanding of this relationship, the factors controlling the water level in a bath

tub must first be considered. The water level will remain the same if the amount of water flowing into

the tub equals that removed through the drain. In the atmosphere, for example, the concentration of a

sulfur compound will remain unchanged if the mean and turbulent fluxes entering a controlled volume

equal those leaving (the flux divergence is zero). On the other hand, concentrations will vary with time

if the flux of sulfur entering the system differs from that leaving, as when plume impaction occurs.

Page 3
How cantheconservationequationbeappliedto measurefluxes?In thefield,fluxesaremeasured

at agivenheightabovethesurface,butthevariableto bedeterminedis therateCO2is takenupby the

surfacebelow.Theverticalflux densityof Swill remainunchangedwith heightif theunderlying

surfaceis 1)homogeneousandextendsupwindfor aconsiderabledistance(thisrequirementensures

thedevelopmentof asurfaceboundarylayer);2) if scalarconcentrationsaresteadywith time;and3)if

nochemicalreactionsareoccurringbetweenthesurfaceandthemeasurement height.

Condition1canbemeteasilythroughpropersiteselection.As arule of thumb,thesiteshouldbe

flat andhorizontallyhomogeneousfor adistancebetween75and100timesthemeasurementheight

(MonteithandUnsworth,1990).Condition2 is metoftenfor manyscalars.Nonsteadyconditionsare

mostaptto occurduringabrupttransitionsbetweenunstableandstableatmosphericthermal

stratification,duringthepassageof afront,or from theimpactionof aplumefromnearbypower

plants.

Eddy Correlation Technique:

The eddy correlation method is a direct method for measuring flux densities of scalar compounds.

The vertical flux density is proportional to the covariance between vertical wind velocity (w) and scalar

concentration fluctuations (c).

A wide range of turbulent eddies contributes to the turbulent transfer of material. Proper

implementation requires sampling across this spectrum of eddies. In frequency domain, eddies

contributing to turbulent transfer having periods between 0.5 and 2000 seconds typically contribute to

mass and energy exchange (Wesely et al., 1989). Hence, wind and chemical instrumentation must be

capable of responding to high-frequency fluctuations. Computer-controlled data acquisition systems

must sample the instrumentation frequently to avoid aliasing and average the signals over a sufficiently

long period to capture all the contributions to the transfer.

On applying the covariance relation, it is assumed implicitly that the mean vertical flux density is

perpendicular to the streamlines of the mean horizontal wind flow. Consequently, the mean vertical

velocity, perpendicular to the streamlines of the mean wind flow, equals zero. In practice, nonzero

vertical velocities occur because of instrument misalignment, sloping terrain, and density fluctuations.

These effects must be removed when processing the data; otherwise, mean mass flow can introduced a

bias error (see Businger, 1986; Baldocchi et al., 1988).

Evaluating the accuracy of the eddy correlation method is complicated. Factors contributing to

instrument errors include time response of the sensor, signal-to-noise ratio, sensor separation distance,

height of the measurement, and signal attenuation caused by path averaging and sampling through a

tube. Natural variability is caused by nonsteady conditions and surface inhomogeneities. Under ideal

conditions, natural variability exceeds about +/- 10%, so it is desirable to design a system with an error

approaching this metric.

Moore (1986) discusses transfer functions for sensor response time and separation distance.

Preliminary calculations of transfer function integrals were performed. Corrections because of sensor

time constants and separation are less than a few percent. Hence, it was decided not to make transfer

function to the flux measurements; the experimental design minimized the need for such corrections

since an open-path infrared gas analyzer (IRGA) and a sonic anemometer were used. Furthermore,

these instruments were placed over a tall rough forest, so small distances in physical displacement have

little impact on the measurement of scalar flux densities.

4. Equipment

4.1 Sensor/Instrument Description

4.1.1 Collection Environment

Measurements were collected continuously through the growing season of 1994. The tower

extended above the canopy and was exposed to direct sunlight and weather. The site operated only

during the growing season; consequently, the temperatures were mild, and freezing conditions were

not encountered.

Page 4
4.1.2 Source/Platform

Above-canopymeasurementsweremadefrom a26-meterdouble-scaffoldwalk-uptower.The

subcanopyflux systemwasmounted2m abovethegroundonaportabletelescopingtower.This

lowertowerwasplaced30to 50m awayfrom thebaseof themaintowerto avoidinterferencefrom

localfoot traffic.

Eddycorrelationflux measurementsweremadeusingatriple-axisAppliedTechnology,Inc.(ATI)

sonicanemometerandaninfraredabsorptionspectrometer.Thesonicanemometermeasuredvertical

(w) andhorizontal(u,v)wind velocityandairtemperature(T).Thisanemometermodelprovides

digitaloutputat arateof 10Hz. TheinfraredabsorptionspectrometermeasuredwatervaporandCO2

densityfluctuations.Thesensorrespondsto frequenciesupto 15Hz andhaslow noiseandhigh

sensitivity(20mg/mUvolt).Thesensorisruggedandexperienceslittle drift overseveralweeksof

continuousoperation.

Soilheatflux densitywasmeasuredby averagingtheoutputof threesoilheatflux plates

(RadiationEnergyBalanceSystems(REBS)modelHFT-3,Seattle,WA). Theywereburied0.01m

belowthesurfaceandwererandomlyplacedwithin afew metersof theflux system.Soiltemperatures

weremeasuredwith two multilevelthermocoupleprobes.Sensorswerespacedlogarithmicallyat 0.02,

0.04,0.08,0.16,and0.32m belowthesurface.Threethermocoupleswereusedto measurebole

temperatures.Sensorswereplacedabout1cm intotheboleandwereazimuthallyspacedaroundatree

atbreastheight.Canopyheatstoragewascalculatedby measuringthetimerateof changein bole

temperaturein thetreetrunks.

Photosyntheticallyactivephotonflux densityandthenetradiationbalanceweremeasuredabove

theforestwith aquantumsensor(LI-CORmodelLI-190S)andanetradiometer(SwisstecoModelS-1

or REBSmodel6),respectively.A moredetailedexperimentaldesignwasimplementedat theforest

floor becausethesolarradiationfield belowaforestcanopyishighly variable(Baldocchiand

Collineau,1994).To accountfor thisvariability,measurementsof solarradiationcomponentswere

madeusinganinstrumentpackagethattraversedslowly acrossa 14.5-m-longtrack.

Air temperatureandrelativehumidityweremeasuredwith appropriatesensors(Campbellmodel

207andVaisalamodelHMP-35A).Wind speedanddirectionweremeasuredwith apropellerwind

speed/directionmonitor(RMYoungmodel05701).Infraredcanopytemperaturewasmeasuredwith

anEverestradiationthermometer(model112C).Thesensorwaspointedsouthandorientedat45

degrees.Ancillary datawereacquiredandloggedonaCampbellCR-21xdatalogger.Half-hour

averageswerestoredonacomputer,to coincidewiththeflux measurements.

CO2concentrationprofilesweremeasuredwith aLI-COR 6262IRGA. Samplesweredrawnat

22, 17,12,6, and2 m.Duringthefirst two IntensiveField Campaigns(IFCs),the22-and17-m

levelsweresampledexclusivelybetween0600and1800hours,andthefull profileatnight.Duringthe

third IFC,thewholeprofilewassampledcontinuously.Solenoidvalveswereswitchedevery30s.

Datafrom thethirdIFC aremostreliablebecausethesystemwasmodifiedto measurecell pressure

andtemperaturein additionto CO2concentration.

Theeddycorrelationflux systemsweredigitizedonthetowerusingtheanalog-to-digital(A/D)

converterof theATI sonicanemometer.TheA/D boardwasa 12-bit system.Digital signalsfor the

threeorthogonalwindvelocitycomponents,temperature,humidity,CO2,andozoneweretransmitted

to a 386computerin thefield lab.In-housesoftware(FLUX.EXE)displayedthedatain realtimeon

screenfor scrutinyandcomputedfluctuationsfrom meansand30-minuteflux covariances.Campbell

21-Xdataloggerswereusedto sampleenvironmentalvariables.Thesedataloggerswereconnectedto

another386computerviadigital lineandwereinterrogatedevery30minutesusingCampbellScientific

software(TELCOM.EXE).

4.1.3 Source/Platform Mission Objectives

The objective was to measure fluxes of sensible and latent heat and CO 2 using the eddy correlation

technique, the radiation balance, and ground heat flux. Sampling, recording, and near-real-time

processing of the data were done with computer-based data loggers.

Page 5
4.1.4 Key Variables

Carbondioxide,solar,sensibleandlatentheatflux densitiesabovetheforestandgroundsurface,

soilheatflux atthesoil surface,andcanopyheatstorage.

4.1.5 Principles of Operation

Sonic Anemometer:

Three-dimensional orthogonal wind velocities (u, v, and w) and virtual temperature (Tv) were

measured with a sonic anemometer (ATI, model SWS-211/3K, Boulder, CO). The path length

between transducers was 0.15 m. The sensor software corrected for transducer shadowing effects (see

Kaimal et al., 1990). Virtual temperature heat flux was converted to sensible heat flux using algorithms

described by Kaimal and Gaynor (1991) and Schotanus et al. (1983).

Infrared Absorption Spectrometer:

Water vapor and CO2 concentrations were measured with an open-path infrared absorption

spectrometer. Details and performance characteristics of the spectrometer are discussed by Auble and

Meyers (1992). In brief, the infrared beam was reflected three times between mirrors separated by

0.20 m, making an 0.80-m absorption path. The response time of the sensor was less than 0.1 s,

sensor noise was less than 300 lag/m3, and its calibration was steady (it varied +/- 3% during the

course of the experiment). The sensor was calibrated periodically with three standard CO2 gases mixed

in air, whose accuracy was + 1%.

Soil Heat Flux Transducer:

An encapsulated thermopile yields a voltage output proportional to the temperature difference

across the top and bottom surfaces. The device has been calibrated in terms of heat flux through

transducer corresponding to the observed temperature difference.

4.1.6 Sensor/Instrument Measurement Geometry

One eddy flux measurement system was placed at 20 m above the ground, on a double-scaffold

tower provided by the BOREAS project. The instruments were mounted on a boom that extended 3 m

upwind of the tower to minimize flow distortion. The boom was 7 m above the mean tree height and

was positioned in the constant flux layer. The azimuth angle of the boom was altered periodically to

place the instrument array into the predominant wind direction. Another eddy flux system was

positioned near the floor of the canopy. The instruments were 1.8 m above the ground. This location

was in the stem space of the canopy and virtually no foliage was present between the canopy floor and

the measurement height.

4.1.7 Manufacturer of Sensor/Instrument

Sonic anemometer:

ATI

6395 Gunpark Dr. Unit E

Boulder, CO 80301

Soil heat transducer:

REBS

P.O. Box 15512

Seattle, WA 98115-0512

Elmer, NJ 08318

Radiation thermometer:

Everest Interscience Inc.

P.O. Box 3640

Fullerton, CA 92634

Page 6
Netradiometer:

REBS

P.O.Box 15512

Seattle,WA 98115-0512

Elmer,NJ08318

Dataloggingsystem:

CampbellScientific

P.O.Box 551,

Logan,UT 84321

4.2 Calibration

4.2.1 Specifications

Thenetradiometer,quantumsensors,andsoilheatflux plateswerecalibratedby themanufacturer.

A netradiometerandquantumsensorwerenew andwereusedasatransferstandard.Theinstruments

were sent to the manufacturer after BOREAS IFC-3 for recalibration. The net radiometer calibrations

did not change over the course of the experiment.

Flux and mean concentration CO2 analyzers were calibrated against standard calibration gases. The

gases were referenced to the Atmospheric Environment Service (AES), World Meteorological

Organization (WMO) standards, and the BOREAS standard gases. The flux sensors were calibrated

two to three times a week. Three reference gases were used to doublecheck linearity. The

concentrations of the standard were about 322, 350, and 400 ppm. The zero and span of the LI-COR

IRGAs were measured nearly every day.

The water vapor sensor was calibrated against mixed air samples and referenced to data from a

chilled mirror dewpoint hygrometer. Stability of the water vapor calibration was checked in the field by

comparing the instrument sensitivity to the output of a Vaisala relative humidity sensor. The relative

humidity sensor was new and calibrated by the manufacturer. The output of the Vaisala relative

humidity sensor was also compared against that of a redundant dewpoint hygrometer. Both sensors

yielded identical humidity measurements.

• Sonic anemometer: supplied by manufacturer. 1.0 m/s/V with sonic path length 0.15 m

• Carbon dioxide: about 30 mg/mUvolt

• Water vapor density fluctuations: varies with vapor density. 2.0 g/m3/volt at 6 °C and 3

g/m3/volt at 14 °C

• Soil heat transducer: about 40 W/m2/mv

• Net radiation: 12 W m2/mv

• Quantum flux density: 180 *mol/m2/s/mv

• Ozone: 28 ppb/volt

4.2.1.1 Tolerance

Solar and net radiation: 1 W/m2

Air temperature fluctuations: 0.1 K

Vertical wind velocity fluctuations: 0.01 m/s

Surface radiative temperature: 0.1 K

4.2.2 Frequency of Calibration

The net radiometers were calibrated before and after the 1994 field campaign. The calibration

coefficient did not change.

The flux sensors were calibrated two to three times a week. The zero and span of the LI-COR

IRGA were measured nearly every day.

4.2.3 Other Calibration Information

None.

Page 7
5. Data Acquisition Methods

The eddy correlation flux systems were digitized on the tower using the A/D converter of the ATI sonic

anemometer. The A/D board was a 12-bit system. Digital signals for the three orthogonal wind velocity

components, temperature, humidity, CO2, and ozone were transmitted to a 386 computer in the field

lab. In-house software (FLUX.EXE) displayed the data in real time on screen for scrutiny and

computed fluctuations from means and 30-minute flux covariances. Campbell 21-X data loggers were

used to sample environmental variables. These data loggers were connected to another 386 computer

via a digital line and were interrogated every 30 minutes using Campbell Scientific software

(TELCOM.EXE).

6.1 Data Notes

None available.

6.2 Field Notes

None available.

6. Observations

7. Data Description

7.1 Spatial Characteristics

7.1.1 Spatial Coverage

All data were collected at the BOREAS SSA-OJP site. The North American Datum of 1983

(NAD83) coordinates of the site are latitude 53.91634 ° N, longitude 104.69203 ° W, and elevation of

579 m.

7.1.2 Spatial Coverage Map

Not applicable.

7.1.3 Spatial Resolution

The data represent point source measurements taken at the given location. The site was relatively

level, and the forest stand was horizontally homogeneous throughout the area deemed as the flux

footprint, a region extending over 1 km upwind.

7.1.4 Projection

Not applicable.

7.1.5 Grid Description

Not applicable.

7.2 Temporal Characteristics

7.2.1 Temporal Coverage

The data were collected nearly continuously from 23-May to 16-Sep-1994.

7.2.2 Temporal Coverage Map

All data were collected at the SSA-OJP site.

Page 8
7.2.3 Temporal Resolution

Data are reported at a 30-minute average.

7.3 Data Characteristics

7.3.1 Parameter/Variable

The parameters contained in the data files on the CD-ROM are:

Column Name

SITE NAME

SUB SITE

DATE OBS

TIME OBS

SENSIBLE HEAT FLUX ABV CNPY

LATENT HEAT FLUX ABV CNPY

NET RAD ABV CNPY

SOIL HEAT FLUX ICM

CO2 FLUX ABV CNPY

CO2 CONC ABV CNPY

CO2 STORAGE

CO2 FLUX ABV PLUS STORAGE

HEAT STORAGE

DOWN PPFD ABV CNPY

WIND DIR ABV CNPY

WIND SPEED ABV CNPY

FRICTION VEL ABV CNPY

AIR TEMP ABV CNPY

ABS HUM ABV CNPY

SOIL TEMP 2CM

SOIL TEMP 4CM

SOIL TEMP 8CM

SOIL TEMP 16CM

SOIL TEMP 32CM

BOLE TEMP ICM

WETNESS SENSOR

OZONE CONC

SENSIBLE HEAT FLUX BELOW CNPY

LATENT HEAT FLUX BELOW CNPY

NET RAD BELOW CNPY

CO2 FLUX BELOW CNPY

CO2 FLUX BELOW PLUS STORAGE

CO2 CONC BELOW CNPY

DOWN PPFD BELOW CNPY

UP PPFD BELOW CNPY

WIND DIR BELOW CNPY

WIND SPEED BELOW CNPY

FRICTION VEL BELOW CNPY

AIR TEMP BELOW CNPY

ABS HUM BELOW CNPY

VAPOR PRESS DEFICIT BELOW CNPY

CRTFCN CODE

REVISION DATE

Page 9
7.3.2 Variable Description/Definition

The descriptions of the parameters contained in the data files on the CD-ROM are:

Column Name Description

SITE NAME

SUB SITE

DATE OBS

TIME OBS

SENSIBLE HEAT FLUX ABV CNPY

LATENT HEAT FLUX ABV CNPY

NET RAD ABV CNPY

SOIL HEAT FLUX ICM

CO2 FLUX ABV CNPY

CO2 CONC ABV CNPY

CO2 STORAGE

CO2 FLUX ABV PLUS STORAGE

HEAT STORAGE

DOWN PPFD ABV CNPY

WIND DIR ABV CNPY

WIND SPEED ABV CNPY

FRICTION VEL ABV CNPY

AIR TEMP ABV CNPY

ABS HUM ABV CNPY

SOIL TEMP 2CM

SOIL TEMP 4CM

SOIL TEMP 8CM

SOIL TEMP 16CM

SOIL TEMP 32CM

BOLE TEMP ICM

WETNESS SENSOR

OZONE CONC

SENSIBLE HEAT FLUX BELOW CNPY

LATENT HEAT FLUX BELOW CNPY

NET RAD BELOW CNPY

CO2 FLUX BELOW CNPY

The identifier assigned to the site by BOREAS, in

the format SSS-TTT-CCCCC, where SSS identifies

the portion of the study area: NSA, SSA, REG,

TRN, and TTT identifies the cover type for the

site, 999 if unknown, and CCCCC is the identifier

for site, exactly what it means will vary with

site type.

The identifier assigned to the sub-site by BOREAS,

in the format GGGGG-IIIII, where GGGGG is the

group associated with the sub-site instrument,

e.g. HYD06 or STAFF, and IIIII is the identifier

for sub-site, often this will refer to an

instrument.

The date on which the data were collected.

The Greenwich Mean Time (GMT) of the start of the

data collection.

The sensible heat flux measured above the canopy.

The latent heat flux measured above the canopy.

The net radiation measured above the canopy.

The surface soil heat flux

The carbon dioxide flux measured above the canopy

The carbon dioxide concentration measured above

the canopy.

The storage term of carbon dioxide under the eddy

flux system.

The sum of the above canopy carbon dioxide flux

and the under flux instrument storage term.

The canopy heat storage.

The incoming photosynthetic photon flux density

measured above the canopy.

The wind direction measured above the canopy.

The wind speed measured above the canopy.

The friction velocity above the canopy.

The air temperature measured above the canopy.

The absolute humidity measured above the canopy.

Soil temperature at 2 cm depth.

Soil temperature at 4 cm depth.

The soil temperature recorded at 8 cm in depth.

The soil temperature recorded at 16 cm in depth.

The soil temperature recorded at 32 cm in depth.

The average bole temperature at 1 cm depth into

tree bole.

The output of the wetness sensor, indicates if

the instruments were wet or dry.

The ozone concentration.

The sensible heat flux measured below the canopy

The latent heat flux measured below the canopy.

The net radiation measured below the canopy.

The carbon dioxide flux measured below the canopy

Page 10
CO2 FLUX BELOW PLUS STORAGE

CO2 CONC BELOW CNPY

DOWN PPFD BELOW CNPY

UP PPFD BELOW CNPY

WIND DIR BELOW CNPY

WIND SPEED BELOW CNPY

FRICTION VEL BELOW CNPY

AIR TEMP BELOW CNPY

ABS HUM BELOW CNPY

The sum of the below canopy carbon dioxide flux

and the under flux instrument storage term.

The carbon dioxide concentration measured below

the canopy.

The downward photosynthetic photon flux density

measured under the canopy.

The upward (reflected) photosynthetic photon flux

density measured under the canopy.

The wind direction measured below the canopy.

The wind speed measured below the canopy.

The friction velocity below the canopy.

The air temperature measured below the canopy.

The absolute humidity measured below the canopy.

VAPOR PRESS DEFICIT BELOW CNPY The vapor pressure deficit measured below the

canopy.

CRTFCN CODE The BOREAS certification level of the data.

Examples are CPI (Checked by PI), CGR (Certified

by Group), PRE (Preliminary), and CPI-??? (CPI

but questionable).

REVISION DATE The most recent date when the information in the

referenced data base table record was revised.

7.3.3 Unit of Measurement

The measurement units for the parameters contained in the data files on the CD-ROM are:

Column Name Units

SITE NAME

SUB SITE

DATE OBS

TIME OBS

SENSIBLE HEAT FLUX ABV CNPY

LATENT HEAT FLUX ABV CNPY

NET RAD ABV CNPY

SOIL HEAT FLUX ICM

CO2 FLUX ABV CNPY

CO2 CONC ABV CNPY

CO2 STORAGE

CO2 FLUX ABV PLUS STORAGE

HEAT STORAGE

DOWN PPFD ABV CNPY

WIND DIR ABV CNPY

WIND SPEED ABV CNPY

FRICTION VEL ABV CNPY

AIR TEMP ABV CNPY

ABS HUM ABV CNPY

SOIL TEMP 2CM

SOIL TEMP 4CM

SOIL TEMP 8CM

SOIL TEMP 16CM

SOIL TEMP 32CM

BOLE TEMP ICM

WETNESS SENSOR

OZONE CONC

[none]

[none]

[DD-MON-YY]

[HHMM GMT]

[Watts] [meter^-2]

[Watts] [meter^-2]

[Watts] [meter^-2]

[Watts] [meter^-2]

[micromoles] [meter^-2] [second^-l]

[parts per million]

[micromoles] [meter^-2] [second^-l]

[micromoles] [meter^-2] [second^-l]

[Watts] [meter^-2]

[micromoles] [meter^-2] [second^-l]

[degrees from North]

[meters] [second^-l]

[meters] [seconds^-l]

[degrees Celsius]

[grams] [meter^-3]

[degrees Celsius]

[degrees Celsius]

[degrees Celsius]

[degrees Celsius]

[degrees Celsius]

[degrees Celsius]

[none]

[ppb]

Page 11
SENSIBLE HEAT FLUX BELOW CNPY

LATENT HEAT FLUX BELOW CNPY

NET RAD BELOW CNPY

CO2 FLUX BELOW CNPY

CO2 FLUX BELOW PLUS STORAGE

CO2 CONC BELOW CNPY

DOWN PPFD BELOW CNPY

UP PPFD BELOW CNPY

WIND DIR BELOW CNPY

WIND SPEED BELOW CNPY

FRICTION VEL BELOW CNPY

AIR TEMP BELOW CNPY

ABS HUM BELOW CNPY

[Watts] [meter^-2]

[Watts] [meter^-2]

[Watts] [meter^-2]

[micromoles] [meter^-2] [seconds^-l]

[micromoles] [meter^-2] [seconds^-l]

[parts per million]

[micromoles] [meter^-2] [second^-l]

[micromoles] [meter^-2] [seconds^-l]

[degrees from North]

[meters] [seconds^-l]

[meters] [seconds^-l]

[degrees Celsius]

[grams] [meter^-3]

VAPOR PRESS DEFICIT BELOW CNPY [kiloPascals]

CRTFCN CODE [none]

REVISION DATE [DD-MON-YY]

7.3.4 Data Source

The source of the parameter values contained in the data files on the CD-ROM are:

Column Name Data Source

SITE NAME

SUB SITE

DATE OBS

TIME OBS

SENSIBLE HEAT FLUX ABV CNPY

LATENT HEAT FLUX ABV CNPY

NET RAD ABV CNPY

SOIL HEAT FLUX ICM

CO2 FLUX ABV CNPY

CO2 CONC ABV CNPY

CO2 STORAGE

CO2 FLUX ABV PLUS STORAGE

HEAT STORAGE

DOWN PPFD ABV CNPY

WIND DIR ABV CNPY

WIND SPEED ABV CNPY

FRICTION VEL ABV CNPY

AIR TEMP ABV CNPY

ABS HUM ABV CNPY

SOIL TEMP 2CM

SOIL TEMP 4CM

SOIL TEMP 8CM

SOIL TEMP 16CM

SOIL TEMP 32CM

BOLE TEMP ICM

WETNESS SENSOR

OZONE CONC

SENSIBLE HEAT FLUX BELOW CNPY

LATENT HEAT FLUX BELOW CNPY

NET RAD BELOW CNPY

CO2 FLUX BELOW CNPY

CO2 FLUX BELOW PLUS STORAGE

[Assigned by BORIS]

[Assigned by BORIS]

[Investigator]

[Investigator]

[Sonic anemometer]

[Infrared Gas Analyzer]

[Net radiometer]

[Soil heat transducer]

[Infrared Gas Analyzer]

[Infrared Gas Analyzer]

[Infrared Gas Analyzer]

[Infrared Gas Analyzer]

[Radiation thermometer]

[Quantum sensor]

[propeller wind speed/direction monitor]

[propeller wind speed/direction monitor]

[Sonic anemometer]

[thermocouple]

[Humidity sensor]

[thermocouple]

[thermocouple]

[thermocouple]

[thermocouple]

[thermocouple]

[thermocouple]

[Wetness sensor]

[Ozone sensor]

[Sonic anemometer]

[Infrared Gas Analyzer]

[Net radiometer]

[Infrared Gas Analyzer]

[Infrared Gas Analyzer]

Page 12
CO2 CONC BELOW CNPY

DOWN PPFD BELOW CNPY

UP PPFD BELOW CNPY

WIND DIR BELOW CNPY

WIND SPEED BELOW CNPY

FRICTION VEL BELOW CNPY

AIR TEMP BELOW CNPY

ABS HUM BELOW CNPY

[Infrared Gas Analyzer]

[Quantum sensor]

[Quantum sensor]

[propeller wind speed/direction monitor]

[propeller wind speed/direction monitor]

[Sonic anemometer]

[thermocouple]

[Humidity sensor]

VAPOR PRESS DEFICIT BELOW CNPY [Humidity sensor]

CRTFCN CODE [Assigned by BORIS]

REVISION DATE [Assigned by BORIS]

7.3.5 Data Range

The following table gives information about the parameter v_ues found in the data files on the

CD-ROM.

Minimum Maximum Missng Unrel Below Data

Data Data Data Data Detect Not

Column Name Value Value Value Value Limit Cllctd

SITE NAME SSA-OJP-FLXTR SSA-OJP-FLXTR None None None None

SUB SITE 9TF05-FLX01 9TF05-FLX01 None None None None

DATE OBS 23-MAY-94 16-SEP-94 None None None None

TIME OBS 0 2330 None None None None

SENSIBLE HEAT FLUX -176.1 497.5 -999 None None Blank

ABV CNPY

LATENT HEAT FLUX ABV -48.1 567.5 -999 None None Blank

CNPY

NET RAD ABV CNPY -76.9 728 -999 None None Blank

-6999

-44.1 97.6 None None None Blank

-16.36 12.93 -999 None None Blank

325 3027.3 None None None Blank

-11.27 11.34 -999 None None Blank

-18.25 17.23 -999 None None Blank

SOIL HEAT FLUX ICM

CO2 FLUX ABV CNPY

CO2 CONC ABV CNPY

CO2 STORAGE

CO2 FLUX ABV PLUS

STORAGE

HEAT STORAGE

DOWN PPFD ABV CNPY

WIND DIR ABV CNPY

WIND SPEED ABV CNPY

FRICTION VEL ABV

CNPY

AIR TEMP ABV CNPY

ABS HUM ABV CNPY

SOIL TEMP 2CM

SOIL TEMP 4CM

SOIL TEMP 8CM

SOIL TEMP 16CM

SOIL TEMP 32CM

BOLE TEMP ICM

WETNESS SENSOR

OZONE CONC

SENSIBLE HEAT FLUX

BELOW CNPY

LATENT HEAT FLUX

-323.3

-i

0

.09

0

2 19

3 86

3 69

4 14

4 587

3 59

-3024

.36

DEW

-29.08

-7896.2

-24 .9

410.1

1947

360

173.199

22 627

29 13

15 53

25 18

22 75

20.39

18.19

16.63

34.97

PPT

35.41

7918.5

476.4

-999 None None Blank

-999 None None Blank

None None None Blank

None None None Blank

-999 None None Blank

-999 None None Blank

None None None Blank

-999 None None Blank

-999 None None Blank

-999 None None Blank

-999 None None Blank

None None None Blank

None None None Blank

None None None Blank

-999 None None Blank

None None None Blank

-999 None None Blank

Page 13
BELOW CNPY

NET RAD BELOW CNPY -265.5

CO2 FLUX BELOW CNPY -15.93

CO2 FLUX BELOW PLUS -17.86

STORAGE

CO2 CONC BELOW CNPY 320

DOWN PPFD BELOW CNPY -31

m m m

UP PPFD BELOW CNPY -13

WIND DIR BELOW CNPY 0

WIND SPEED BELOW .009

CNPY

FRICTION VEL BELOW 0

CNPY

AIR TEMP BELOW CNPY -2.5

ABS HUM BELOW CNPY .22

VAPOR PRESS DEFICIT .5

BELOW CNPY

CRTFCN CODE

REVISION DATE

241.1 -999 None None Blank

13.61 -999 None None Blank

14.09 -999 None None Blank

619 -999 None None Blank

1548 -999 None None Blank

346 -999 None None Blank

360 None None None Blank

173.199 None None None Blank

3.885 -999 None None Blank

31.44 -999 None None Blank

15.01 None None None Blank

4.59 -999 None None Blank

CPI CPI None None None None

14-MAY-98 19-JUN-98 None None None None

Minimum Data Value -- The minimum value found in the column.

Maximum Data Value -- The maximum value found in the column.

Missng Data Value -- The value that indicates missing data. This is used to

indicate that an attempt was made to determine the

parameter value, but the attempt was unsuccessful.

Unrel Data Value -- The value that indicates unreliable data. This is used

to indicate an attempt was made to determine the

parameter value, but the value was deemed to be

unreliable by the analysis personnel.

Below Detect Limit -- The value that indicates parameter values below the

instruments detection limits. This is used to

indicate that an attempt was made to determine the

parameter value, but the analysis personnel determined

that the parameter value was below the detection

limit of the instrumentation.

Data Not Cllctd -- This value indicates that no attempt was made to

determine the parameter value. This usually

indicates that BORIS combined several similar but

not identical data sets into the same data base table

but this particular science team did not

measure that parameter.

Blank -- Indicates that blank spaces are used to denote that type of value.

N/A -- Indicates that the value is not applicable to the respective column.

None -- Indicates that no values of that sort were found in the column.

Page 14
7.4 Sample Data Record

The following are wrapped versions of data record from a sample data file on the CD-ROM.

SITE NAME,SUB SITE,DATE OBS,TIME OBS,SENSIBLE HEAT FLUX ABV CNPY,

LATENT HEAT FLUX ABV CNPY,NET RAD ABV CNPY, SOIL HEAT FLUX ICM, CO2 FLUX ABV CNPY,

CO2 CONC ABV CNPY,CO2 STORAGE,CO2 FLUX ABV PLUS STORAGE,HEAT STORAGE,

DOWN PPFD ABV CNPY,WIND DIR ABV CNPY,WIND SPEED ABV CNPY,FRICTION VEL ABV CNPY,

AIR TEMP ABV CNPY,ABS HUM ABV CNPY, SOIL TEMP 2CM, SOIL TEMP 4CM, SOIL TEMP 8CM,

SOIL TEMP 16CM, SOIL TEMP 32CM, BOLE TEMP ICM, WETNESS SENSOR, OZONE CONC,

SENSIBLE HEAT FLUX BELOW CNPY, LATENT HEAT FLUX BELOW CNPY,NET RAD BELOW CNPY,

CO2 FLUX BELOW CNPY,CO2 FLUX BELOW PLUS STORAGE,CO2 CONC BELOW CNPY,

DOWN PPFD BELOW CNPY,UP PPFD BELOW CNPY,WIND DIR BELOW CNPY,

WIND SPEED BELOW CNPY,FRICTION VEL BELOW CNPY,AIR TEMP BELOW CNP

Y,ABS HUM BELOW CNPY,VAPOR PRESS DEFICIT BELOW CNPY,CRTFCN CODE,REVISION DATE

'SSA-OJP-FLXTR', '9TF05-FLX01',01-JUL-94,0,7.1,2.6,84.3 -17.3 3 05,360.7,-4.2,

-1.16,30.3,285.0,310.0, .99, .132,8.06,7.91,8.43,,,10.76 11.17 5 23, 'DRY',3.92,

.............. 'CPI',I2-JUN-98

'SSA-OJP-FLXTR', '9TF05-FLX01',01-JUL-94,30,5.4,22.3,37 8,-12 6 2.3,348.3,-6.11,

-3.82,50.5,226.0,288.0, .72, .i19,10.22,8.26,8.84,,,i0.72,11.15,6.13, 'DRY',4.06,

.............. 'CPI',I2-JUN-98

8. Data Organization

8.1 Data Granularity

The smallest unit of data tracked by the BOREAS Information System (BORIS) was data collected

at a given site on a given date.

8.2 Data Format

The Compact Disk-Read-Only Memory (CD-ROM) files contain American Standard Code for

Information Interchange (ASCII) 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.

Each data file on the CD-ROM has four header lines of Hyper-Text Markup Language (HTML)

code at the top. When viewed with a Web browser, this code displays header information (data set

title, location, date, acknowledgments, etc.) and a series of HTML links to associated data files and

related data sets. Line 5 of each data file is a list of the column names, and line 6 and following lines

contain the actual data.

9. Data Manipulations

9.1 Formulae

9.1.1 Derivation Techniques and Algorithms

Sample computer code displaying processing methods:

Sensible Heat Flux

1) Test if flux covariances are significantly different from zero for 18000 samples

--Is wT non-zero?

Page 15
IF TT > 0 THEN

SlGT = TT ^ .5

RWT = WT / (SlGW * SlGT)

ELSE

RWT : 0

END IF

IF ABS (RWT) < .0146 THEN WT = 0

--correct virtual temperature heat flux from sonic to actual heat flux.

--We apply the formula of Kaimal and Gaynor 1991. Bound. Layer Met.

--The Schotanus et al. 1983 BLM correction is not needed for the

--ATI sonic (-2 T u w'u'/c^2)

SPECIFIC HUMIDITY : ABSOLUTE HUMIDITY / (AIR DENSITY * i000)

--Heat capacity of air weight by the moist and dry air contributions

CP AIR : i010 * AIR DENSITY + 4182 * ABSOLUTE HUMIDITY

SIG : ABSOLUTE HUMIDITY/ (i000 * AIR DENSITY)

SIGTOT : ABSOLUTE HUMIDITY/1000 / (ABSOLUTE HUMIDITY/1000 + AIR DENSITY)

2) Correct the sonic derived sensible heat fluxes to the actual sensible heat flux.

--Note: WTCORR should be in the WE calculation, hence looping

--is needed between sensible and latent heat flux computations

WTGUESS = WT SONIC

CCC : 0

NEWWE:

WTCORR = (WT SONIC - .51 * TK * WQQ) --K m/s

IF ABS(WTCORR - WTGUESS) > .00001 THEN

CCC = CCC + 1

IF CCC > i0 THEN GOTO OUTWE

WTGUESS : WTCORR

GOTO NEWWE

END IF

OUTWE:

SENSIBLE HEAT FLUX : WTCORR * CP AIR

Water Vapor and Latent Heat Flux Densities

1) 'Is wq covariance non-zero?

--W/m 2

IF WW > 0 THEN

SIGW = WW ^ .5

ELSE

SIGW = 9999

END IF

IF QQ > 0 THEN

SIGQ = QQ ^ .5

Page 16
RWQ = WQ / (SIGW * SIGQ)

ELSE

RWQ = 0

END IF

IF ABS (RWQ) < .0146 THEN WQ = 0

WQX = WQ COVARIANCE * H2OCAL --g/m2/s

2) Compute latent heat flux by considering temperature variations in the latent heat of vaporization.

LFUSION = 334000

LATENT HEAT = 3149000 - 2370 * TAIR K

IF TK < 273 THEN LATENT HEAT = LAMBDA + LFUSION

LAMBDA = LATENT HEAT / i000

3) Apply Webb et al density correction for E. Units are Ecorr (g/m2/s)

ECORR = (i + SIG * 1.6077) * (WQX + ABSOLUTE HUMIDITY * WTGUESS / TK)

--factor of i000 is needed to change ECORR from g/m s to

--kg m-3, so units cancel when divided by rhoa

WQQ = ECORR * (i - SPECIFIC HUMIDITY) / (i000 * (AIR DENSITY +

ABSOLUTE HUMIDITY/1000)) --m/s

LATENT HEAT FLUX = LAMBDA * WQX --(W/m 2)

CO2 Flux Densities

WC = WC COVARIANCE * CO2CAL --mg/m2 /s

1) Apply Webb et al. corrections for CO2 and latent heat fluxes

CO2CONC = CO2 DENSITY * 8.314 * TK / (PRESS KPA * 44.01)

NU = CO2CONC* 44.01 / (28.96 * i000000)

SIG = ABSOLUTE HUMIDITY / (AIR DENSITY * i000)

SIGTOT = (ABSOLUTE HUMIDITY / i000) / (AIR DENSITY + ABSOLUTE HUMIDITY / i000)

TERM1 = 1.6077 * NU * LATENT HEAT FLUX / LAMBDA

H=SENSIBLE HEAT FLUX

TERM2 = (i + SIG * 1.6077) * RHOC * H / (TK * AIR DENSITY * 1005)

FC CORR = WC + TERM1 + TERM2

Canopy Heat Storage

Define canopy biomass and representative specific heat by weighting the water and cellulose

contributions.

1) define volume of vegetation as the product of canopy height and its basal area.

JACK PINE: height = 13.5 m; basal area=22 m2/ha

2) heat transfer coefficient is volume x Cp/time for 30 minutes

CP=4.175 MJ/M3/C for water

CP=2.500 MJ/M3/C for cellulose

3) Computed canopy heat capacity using Gower's (TE-06) biomass data

Page 17
a) bole contribution

PLANT COEF = 19.9 --W/m2/C/s

CGI : DELTA BOLE TEMPERATURE * PLANT COEF

TBOLOLD : TBOL

b) heat storage in the air layer

DELTA AIR TEMPERATURE = TAVG - TOLD

c) branch and needle heat storage

CGIA = 3.9 * DELTAIR

CG2 = DELTAIR * 12.8

TOLD = TAVG

'20xl.15x1005/1800s

d) latent heat storage in air layer of canopy

DELTA RHOV = RHOVAVG - RHOVOLD

CG3 = 27.1 * DELRHOV --20x2442/1800

RHOVOLD : RHOVAVG

CANOPY HEAT STORAGE : CGI + CGIA + CG2 + CG3

9.2 Data Processing Sequence

9.2.1 Processing Steps

Flux covariances were computed in the field by the data acquisition program. Back at home,

calibrations were double- and triple-checked by comparing old and new calibrations and by comparing

the mean response of the scalar flux sensors against independent meteorological instruments. Tests

were made for energy balance closure to ensure that the data were of reliable quality. Programs were

then run to delete periods when the sensors were offline, off range, being maintained, or unreliable

because of rain or instrument malfunction.

BORIS staff processed these data by:

• Reviewing the initial data files and loading them online for BOREAS team access.

• Designing relational data base tables to inventory and store the data.

• Loading the data into the relational data base tables.

• Working with the team to document the data set.

• Extracting the data into logical files.

9.2.2 Processing Changes

None.

9.3 Calculations

9.3.1 Special Corrections/Adjustments

Eddy fluctuations:

CO2 DENSITY = CO2PPM * AIR DENSITY * 44 / 29 --rag m-3

9.3.2 Calculated Variables

None.

9.4 Graphs and Plots

None.

Page 18
10. Errors

10.1 Sources of Error

Factors contributing to instrument errors include time response of the sensor, signal-to-noise ratio,

sensor separation distance, height of the measurement, and signal attenuation caused by path averaging

and sampling through a tube. Natural variability is caused by nonsteady conditions and surface

inhomogeneities. Under ideal conditions, natural variability exceeds about + 10%.

10.2 Quality Assessment

10.2.1 Data Validation by Source

Surface energy balance was tested by comparing measurements of available energy against the sum

of latent and sensible heat flux. Tests over the jack pine stand showed that the eddy flux system closes

the surface energy balance within 12% and that this degree of closure is comparable with the

state-of-the-art demonstrated in the literature.

Several independent checks have been made on components of this data set. The Vaisala humidity

sensor was compared against a dewpoint hygrometer, and the comparison was excellent. The output of

the net radiometer was compared against measurements made on Tim Crawford's airplane (Airborne

Fluxes and Meteorology (AFM)-01). There was no bias between the measurements, suggesting that

the impact of the net radiometer seeing the tower structure was small.

10.2.2 Confidence Level/Accuracy Judgment

The following are the best estimates of accuracy for a single flux estimate:

Net radiation ± 4 to 7%

Soil heat flux ± 10%

Latent heat flux ± 15 to 20% or ±30 W m 2,

Sensible heat flux ± 15 to 20% or ±30 W m 2,

whichever is larger

whichever is larger

None of these estimates addresses the variability of flux estimates from site to site.

• Detection limit of CO2 flux system: 0.01 mg/m2/s

• The intermittence of turbulence limits the sampling error of turbulent fluxes to 10 to 20%. In

addition, measurement errors must be accounted for. Fortunately, a large amount of statistical

averaging reveals stable fluxes and small bias errors (< 12%) on the surface energy fluxes.

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.

Page 19
11. Notes

11.1 Limitations of the Data

Flux data were collected during the growing season of 1994; no wintertime data were acquired.

11.2 Known Problems with the Data

Data have been rejected when:

• The voltages of the CO2 and water vapor sensor were nearly or entirely off scale.

• The log book denoted problems with specific sensors.

• The gas analyzer was calibrated or when the instrument boom was moved.

• Flux runs were less than 15 minutes.

• The mean vertical velocity of the sonic anemometer exceeded 0.3 m/s (an indication of water

on the transducer or continued spiking).

• Friction velocity exceeded 1.5 m/s.

Values during these periods have been assigned values of -999 (or -6999).

The third order screening of the data deleted data that were several standard deviations greater than

the population means and were true spikes and outliers. The following data were deleted:

• LE fluxes greater than 350 W/m2 and less than -50 W/m2.

• CO2 fluxes greater than 0.50 mg/mZ/s and less than -0.75 mg/ng/s.

Be careful when using data during WET periods, i.e. when the WETNESS_SENSOR has a value of

WET. These periods have not been screened and are retained to complete the record. Problems may

occur because the domes on the radiometers were wet and water films may be covering optics of the

IRGA and the transducer of the sonic anemometer. When using these data to test models, it is

recommended that data from wet periods not be included!

Be careful about using data when wind was blowing through the tower; these data have not been

deleted from the record. Closure of the surface energy balance was diminished during these periods,

and an upwind bias on the vertical wind velocity, caused by aerodynamic distortion from the tower,

was noted. Wind directions to be cautious about are in the zone between 350 and 60 degrees. When

using these data to test models, it is recommended that data from nonideal wind directions be omitted.

Mean CO2 concentrations were assigned values of 350 when the sensor was out of range. Also be

cautious about using the mean CO2 concentrations. There were some zero and span drifting problems

with the IRGA. Typical midday CO2 concentration should be on the order of 330 and 350 ppm. Data

exceeding 400 ppm would have bypassed data filters and would be spurious.

The mean CO2 concentration calibrations have been double-checked and an attempt was made to

compensate for drift from calibration to calibration. Sometimes the drift was small; other times it was

between -10 and +10 ppm over a few days. At this point the relative change in CO2 from hour to hour

is OK. Use the absolute values with much skepticism and caution. These data should not be used to

assess the seasonal change in CO2 over the boreal region.

Periods when calibrating or moving boom, given as day number and ending time of the half-hour

observation (Central Standard Time):

DOY Time

143 1300

145 1130

150 ii00

150 1300

151 0930

153 1030

154 0930

154 1630

Page 20
155

156

161

163

164

164

164

164

179

188

189

189

ii00

1130

0930

1030

0930

1030

0930

i000

1530

1300

1300

1330

from 200

201 1130

204 1230

210 i000

211 0930

215 1130

242 1500

242 1300

245 1400

1400 through 200 1500

from 247 1400 through 248 i000

253 ii00

Periods when net radiometer and incident Photosynthetically Active Radiation (PAR) sensor were

shaded by the tower, given as day number and ending time of the half-hour observation (Central

Standard Time):

from 145 0800 through 145 0930

from 146 0800 through 146 0930

from 147 0800 through 147 0930

from 148 0800 through 148 0930

from 149 0800 through 149 0930

from 150 0800 through 150 0930

from 151 0800 through 151 0930

CO2 Concentration Data:

The absolute quality of the LI-COR C02 data is uncertain. The instrument was new to the

investigator and seemed to be unstable. Calibrations were conducted almost every day, but the zero

and span seemed to drift. Some first-order corrections are being made to put the values in line with

reality, but more work needs to be done. The quality of these data is especially called into question

because the investigator is now using a brand new sensor in Oak Ridge and automatically zeroing and

spanning the sensor every day, and has not seen the zero or span change for 3 months. Spurious CO2

values may be real, however, if smoke from forest fires were a problem. Thus, there are some

reservations about accepted elevated CO2 values.

11.3 Usage Guidance

CAUTION should be exercised when using flux data for several hours surrounding dawn and

dusk, since these are periods of unsteady conditions. In addition, nighttime data should be scrutinized.

11.4 Other Relevant Information

None given.

Page 21
12. Application of the Data Set

These data are useful for the study of water, energy, and carbon exchange in a mature jack pine forest.

None.

13. Future Modifications and Plans

14. Software

14.1 Software Description

Some samples of code used in the analysis are shown in Section 9.1.1.

14.2 Software Access

None given.

15. Data Access

The TF-05 SSA-OJP tower flux and meteorological data are available from the Earth Observing

System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed

Active Archive Center (DAAC).

15.1 Contact Information

For BOREAS data and documentation please contact:

ORNL DAAC User Services

Oak Ridge National Laboratory

P.O. Box 2008 MS-6407

Oak Ridge, TN 37831-6407

Phone: (423) 241-3952

Fax: (423) 574-4665

E-mail: ornldaac@ornl.gov or ornl@eos.nasa.gov

15.2 Data Center Identification

Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory

(ORNL) Distributed Active Archive Center (DAAC) for Biogeochemical Dynamics

http://www-eosdis.ornl.gov/.

15.3 Procedures for Obtaining Data

Users may obtain data directly through the ORNL DAAC online search and order system

[http://www-eosdis.ornl.gov/] and the anonymous FTP site [ftp://www-eosdis.ornl.gov/data/] or by

contacting User Services by electronic mail, telephone, fax, letter, or personal visit using the contact

information in Section 15.1.

15.4 Data Center Status/Plans

The ORNL DAAC is the primary source for BOREAS field measurement, image, GIS, and

hardcopy data products. The BOREAS CD-ROM and data referenced or listed in inventories on the

CD-ROM are available from the ORNL DAAC.

Page 22
16. Output Products and Availability

16.1 Tape Products

None.

16.2 Film Products

None.

16.3 Other Products

These data are available on the BOREAS CD-ROM series.

17. References

17.1 Platform/Sensor/Instrument/Data Processing Documentation

None.

17.2 Journal Articles and Study Reports

Amiro, B.D. 1990. Comparison of turbulence statistics within three boreal forest canopies. Boundary

Layer Meteorology. 51:00-121.

Auble, D.L. and T.P. Meyers. 1992. An open path, fast response infrared-absorption gas analyzer for

H20 and CO2. Boundary Layer Meteorology. 59:243-256.

Baldocchi, D.D. and C.A. Vogel. 1995. Energy and C02 flux densities above and below a temperate

broad-leaved forest and boreal pine forest. Tree Physiology, Volume 16, March 1995, pp. 5-16.

Baldocchi, D.D. and T.P. Meyers. 1991. Trace gas exchange above the floor of a deciduous forest, l:

Evaporation and CO2 efflux. J. Geophys. Res. 96:7271-7285.

Baldocchi, D.D., B.B. Hicks, and T.P. Meyers. 1988. Measuring biosphere-atmosphere exchanges

of biologically related gases with micrometeorological methods. Ecology, 69:1331-1340.

Baldocchi, D.D., C.A. Vogel, and B. Hall. 1997. Seasonal variation of carbon dioxide exchange rates

above and below a boreal jack pine forest. Agricultural and Forest Meteorology 83: 147-170.

Baldocchi, D.D., C.A. Vogel, and B. Hall. 1997. Seasonal variation of energy and water vapor

exchange rates above and below a boreal jack pine forest canopy. Journal of Geophysical Research

102(D24): 28,939-28,951.

Baldocchi DD, S.B. Verma, and D.E. Anderson DE. 1987. Canopy photosynthesis and water-use

efficiency in a deciduous forest. Journal of Applied Ecology 24: (1) 251-260. Businger, J.A. 1986.

Evaluation of the accuracy with which dry deposition can be measured with current

micrometeorological techniques. J. Clim. and Appl. Meteorol. 25:1100-1124.

Kaimal, J.C. and J.E. Gaynor. 1991. Another look at sonic thermometry. Boundary Layer

Meteorology. 56:401-410.

Kaimal, J.C., J.E. Gaynor, H.A. Zimmerman, and G.A. Zimmerman. 1990. Minimizing flow

distortion errors in a sonic anemometer. Boundary Layer Meteorology. 53:103-115.

Mcmillen, R.T. 1988. An eddy-correlation technique with extended applicability to non-simple terrain.

Boundary-Layer Meteorology 43: (3) 231-245.

Page 23
Monteith, J.L.andM.H. Unsworth.1990.Principlesof EnvironmentalPhysics.EdwardArnold,

London.

Moore,C.J.1986.Frequencyresponsecorrectionsfor eddycorrelationmeasurements. Boundary

LayerMeteorology.37:17-35.

Newcomer,J.,D. Landis,S.Conrad,S.Curd,K. Huemmrich,D. Knapp,A. Morrell, J.Nickeson,

A. Papagno,D. Rinker,R.Strub,T. Twine,F. Hall, andP.Sellers,eds.2000.CollectedDataof The

BorealEcosystem-AtmosphereStudy.NASA. CD-ROM.

Schotanus,P.,F.T.M. Nieuwstadt,andH.A.R.DeBruin. 1983.Temperaturemeasurementwith a

sonicanemometerandits applicationto heatandmoisturefluxes.BoundaryLayerMeteorology.26:

81-93.

Sellers,P.andF.Hall. 1994.BorealEcosystem-AtmosphereStudy:ExperimentPlan.Version

1994-3.0,NASA BOREASReport(EXPLAN 94).

Sellers,P.andF.Hall. 1996.BorealEcosystem-AtmosphereStudy:ExperimentPlan.Version

1996-2.0,NASA BOREASReport(EXPLAN 96).

Sellers,P.,F. Hall, andK.F. Huemmrich.1996.BorealEcosystem-AtmosphereStudy:1994

Operations.NASA BOREASReport(OPSDOC94).

Sellers,P.,F. Hall, andK.F. Huemmrich.1997.BorealEcosystem-AtmosphereStudy:1996

Operations.NASA BOREASReport(OPSDOC96).

Sellers,P.,F. Hall, H. Margolis,B. Kelly, D. Baldocchi,G. denHartog,J.Cihlar, M.G. Ryan,B.

Goodison,P.Crill, K.J.Ranson,D. Lettenmaier,andD.E. Wickland. 1995.Theboreal

ecosystem-atmospherestudy(BOREAS):anoverviewandearlyresultsfrom the1994field year.

Bulletinof theAmericanMeteorologicalSociety.76(9):1549-1577.

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, andF.E.Guertin.1997.BOREAS

in 1997:ExperimentOverview,ScientificResultsandFutureDirections.Journalof Geophysical

Research102(D24):28,731-28,770.

Verma,S.B.,D.D. Baldocchi,D.E.Anderson,D.R. Matt, andR.J.Clement.1986.Eddyfluxesof

CO2,watervapor,andsensibleheatoveradeciduousforest.Boundary-LayerMeteorology36:71-91.

Wesely,M.L., D.H. Lenschow,andO.T.Denmead.1989.Flux measurementtechniques.In: Global

TroposphericChemistry- ChemicalFluxesin theGlobalAtmosphere.D.H. LenschowandB.B.

Hicks (eds.).Reportof theWorkshopontheMeasurementsofSurfaceExchangeandFlux Divergence

of ChemicalSpeciesin theGlobalAtmosphere.pp.31-46.Preparedby theNationalCenterfor

AtmosphericResearch,Boulder,CO. 107pp.

17.3 Archive/DBMS Usage Documentation

None.

None.

18. Glossary of Terms

Page 24
A/D

AES

AFM

ASCII

ATDD

ATI

BOREAS

BORIS

CD-ROM

DAAC

EOS

EOSDIS

GIS

GMT

GSFC

HTML

IFC

IRGA

NAD83

NASA

NOAA

NSA

OJP

ORNL

PANP

PAR

PPFD

REBS

SSA

TE

TF

URL

WMO

19. List of Acronyms

- Analog-to-Digital

- Atmospheric Environment Service

- Airborne Fluxes and Meteorology

- American Standard Code for Information Interchange

- Atmospheric Turbulence and Diffusion Division

- Applied Technology, Inc.

- BOReal Ecosystem-Atmosphere Study

- BOREAS Information System

- Compact Disk-Read-Only Memory

- Distributed Active Archive Center

- Earth Observing System

- EOS Data and Information System

- Geographic Information System

- Greenwich Mean Time

- Goddard Space Flight Center

- HyperText Markup Language

- Intensive Field Campaign

- Infrared Gas Analyzer

- North American Datum of 1983

- National Aeronautics and Space Administration

- National Oceanic and Atmospheric Administration

- Northern Study Area

- Old Jack Pine

- Oak Ridge National Laboratory

- Prince Albert National Park

- Photosynthetically Active Radiation

- Photosynthetic Photon Flux Density

- Radiation Energy Balance Systems

- Southern Study Area

- Terrestrial Ecology

- Tower Flux

- Uniform Resource Locator

- World Meteorological Organization

20. Document Information

20.1 Document Revision Date

Written: 05-Mar- 1996

Revised: 30-Jul- 1999

20.2 Document Review Date(s)

BORIS Review: 20-MAY- 1998

Science Review: 04-AUG- 1998

20.3 Document ID

None.

Page 25
20.4 Citation

When using these data, please include the following acknowledgment as well as citations of

relevant papers in Section 17.2:

Scalar and energy flux data (e.g., C02, water vapor, sensible heat, and solar energy):

Coauthorship if there is extensive use of the data. Acknowledgment if a few data are used to make

a supporting point.

Meteorological data:

Acknowledgment: Field data obtained and prepared by Dennis Baldocchi and Christoph Vogel.

Atmospheric Turbulence and Diffusion Division, NOAA P.O. Box 2456, Oak Ridge, TN 37831

If using data from the BOREAS CD-ROM series, also reference the data as:

Baldocchi, D. and C. Vogel, "Experimental and Modeling Studies of Water Vapor, Sensible Heat,

and CO2 Exchange Over and Under a Boreal Forest." In Collected Data of The Boreal

Ecosystem-Atmosphere Study. Eds. J. Newcomer, D. Landis, S. Conrad, S. Curd, K. Huemmrich,

D. Knapp, A. Morrell, J. Nickeson, A. Papagno, D. Rinker, R. Strub, T. Twine, F. Hall, and P.

Sellers. CD-ROM. NASA, 2000.

Also, cite the BOREAS CD-ROM set as:

Newcomer, J., D. Landis, S. Conrad, S. Curd, K. Huemmrich, D. Knapp, A. Morrell, J.

Nickeson, A. Papagno, D. Rinker, R. Strub, T. Twine, F. Hall, and P. Sellers, eds. Collected Data of

The Boreal Ecosystem-Atmosphere Study. NASA. CD-ROM. NASA, 2000.

20.5 Document Curator

20.6 Document URL

Page 26
REPORT DOCUMENTATION PAGE FormApproved

OMB No. 0704-0188

Public reporting burden for this collection of informationis estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources,

gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this

collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson

Davis Highway, Suite 1204, Arlington, VA 22202-4302, and to the Office of Management and Budget, Paperwork Reduction Project (0704-0188), Washington, DC 20503.

1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE 3. REPORT TYPE AND DATES COVERED

October 2000 Technical Memorandum

4. TITLE AND SUBTITLE 5. FUNDING NUMBERS

Technical Report Series on the Boreal Ecosystem-Atmosphere Study (BOREAS)

BOREAS TF-5 SSA-OJP Tower Flux and Meteorological Data 923

6. AUTHOR(S) RTOP: 923-462-33-01

Dennis Baldocchi and Christoph Vogel

Forrest G. Hall and Karl Huemmrich, Editors

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS (ES)

Goddard Space Flight Center

Greenbelt, Maryland 20771

9. SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS (ES)

National Aeronautics and Space Administration

Washington, DC 20546-0001

8. PEFORMING ORGANIZATION

REPORT NUMBER

2000-03136-0

10. SPONSORING / MONITORING

AGENCY REPORT NUMBER

TM--2000-209891

Vol. 200

11. SUPPLEMENTARY NOTES

D. Baldocchi & C. Vogel: National Oceanic and Atmospheric Administration/ATDD, Oakridge, Tenn.;

K. Huemmrich: Univ. of Maryland, NASA Goddard Space Flight Center Greenbelt, Maryland

12a. DISTRIBUTION / AVAILABILITY STATEMENT

Unclassifie_Unlimited

Subject Category: 43

Report available from the NASA Center for AeroSpace Information,

7121 Standard Drive, Hanover, MD 21076-1320. (301) 621-0390.

12b. DISTRIBUTION CODE

13. ABSTRACT (Maximum 200 words)

The BOREAS TF-5 team collected tower flux data at the BOREAS SSA-OJP site through the growing

season of 1994. The data are available in tabular ASCII files.

14. SUBJECT TERMS

BOREAS, tower flux.

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OF REPORT

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