BOREAS TF-02 SSA-OA Tower Flux, Meteorological, and Precipitation Data Summary The BOREAS TF-02 team collected energy, carbon dioxide, water vapor, and momentum flux data above the canopy and in profiles through the canopy, along with meteorological data at the BOREAS SSA-OA site. Above-canopy measurements began in early February and ran through mid-September of 1994. Measurements were collected over a longer period of 1994 than most BOREAS flux sites. Daily precipitation data from several gauges were also collected. 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-02 SSA-OA Tower Flux, Meteorological, and Precipitation Data 1.2 Data Set Introduction The Tower Flux (TF)-02 team collected heat, carbon dioxide, water vapor, and momentum fluxes along with meteorological data measured from the BOReal Ecosystem-Atmosphere Study (BOREAS) Southern Study Area (SSA) Old Aspen (OA) tower. Measurements were collected at several different heights within and above the forest canopy to produce profiles of several variables, including sensible heat flux, latent heat flux, air density, wind speed and direction, friction velocity, momentum flux, CO2 concentration and flux, water vapor flux, air temperature, vapor pressure, and dewpoint temperature. Data collection began in early February 1994, making this site the earliest BOREAS flux tower to collect data in 1994. 1.3 Objective/Purpose The general objective was to study CO2 and water vapor exchange between the forest and atmosphere at the SSA-OA site. Specific objectives were: * To measure the fluxes of sensible heat, H2O and CO2 above and within the aspen stand throughout the year. * To obtain from the CO2 flux data estimates of gross photosynthesis and respiration. * To determine the contribution of the hazelnut understory to net ecosystem productivity (NEP). * To determine the effects of environmental factors on stand evapotranspiration and NEP. * To take part in the development of procedures for scaling up component fluxes to the stand level. * To study the processes controlling turbulent transfer of H2O and CO2 within the stand. * To take part in the evaluation of methods of estimating nocturnal CO2 in and above the stand. 1.4 Summary of Parameters Profiles through the forest canopy of the following variables were measured: latent heat flux, latent heat storage, sensible heat flux, air density, CO2 flux, CO2 concentration, CO2 storage flux, momentum flux, air temperature, wind speed and direction, friction velocity, standard deviation of the vertical wind speed, water vapor flux, and virtual heat flux. Other measurements include net radiation, incident and reflected photosynthetic photon flux density (PPFD), incident shortwave radiation, air pressure, relative humidity, canopy surface temperature, absolute humidity, ozone concentration, and precipitation. 1.5 Discussion In 1993 and 1994, the TF-01 group measured fluxes under the canopy at the SSA-OA site, while the TF-02 group measured above-canopy fluxes and profiles at that site. In 1996, the TF-01 group moved its equipment to the top of the 39-meter tower to measure above-canopy fluxes; this document describes the TF-02 1994 data collection effort. The TF-02 group operated an eddy correlation system at the 39-m height. It consisted of a 3-D sonic anemometer (model DAT-310 with model TR-61B probe, Kaijo-Denki, Tokyo, Japan) with a 20-cm path length, a model 6262 Infrared Gas Analyzer (IRGA), and an ozone sensor. Air was drawn at 6.5 l min-1 down 6-m long heated 3.2-mm inner diameter (i.d.) Bev-a-line sampling tubing, then pumped through the sample cell using two diaphragm pumps (model TD-4X2N, Brailsford Co. Rye, NY) connected in parallel. To prevent condensation, the sampling tubing was heated (2-3 ºC above ambient) by passing an electric current through 20-AWG nichrome wire (about 15 ohms resistance) coiled around the exterior of the tubing. Sample cell pressure was approximately atmospheric pressure and the delay time was 1.2 s. The IRGA was operated in differential mode with 320 mmol mol-1 CO2 in dry air flowing through the reference cell at 30 cm3 min-1. TF-02 also operated 3-D sonic anemometers at 28.6, 18.6, 5.9 (all TR-61B probes), and 0.5 m (miniature probe). A second University of British Columbia (UBC) IRGA unit was used with the 28.6, 5.9, and 0.5 m units during selected periods in 1994 (see P.C. Yang's Ph.D. thesis, 1998). Other measurements included air temperatures using aspirated platinum resistance thermometers (at 0.8, 2.3, 6.8, 9.9, 13.0, 16.1, 19.2, 22.3, 25.4, 30.1, and 34.6 m), downward total and diffuse solar (model PSP pyranometer, The Eppley Laboratory, Inc., Newport, RI), downward longwave (Eppley model PIR pyrgeometer) and net radiation (Middleton model CN-1 net radiometer), PPFD (LI-COR model 190- SB quantum sensor) above the forest (at 33-m height from the ground), air humidity above (model M1 dewpoint hygrometer with a model D2 sensor, General Eastern Instruments Corp., Watertown, MA) and below (model HMP-35C sensor, Vaisala, Inc., Woburn, MA) the overstory, wind speed and direction above and below the overstory (model 05031 vane propeller anemometer, R.M. Young Co., Traverse City, MI), and infrared surface temperatures of the aspen and hazelnut canopies (model 4000 IR thermometer, Everest Interscience, Inc., Fullerton, CA). Precipitation was measured using a weighing rain gauge (Belfort Instrument Co., Baltimore, MD). In addition, TF-02 operated a CO2 concentration profile system, consisting of eight levels: 0.8, 2.3, 9.5, 15.7, 18.8, 21.9, 25, and 34.5 m. Air was drawn through heated Dekoron tubing (9.3-mm inner diameter) by a rotary pump and pushed through a LI-COR 6262 IRGA by a small diaphragm pump. 1.6 Related Data Sets BOREAS TF-01 SSA-OA Soil Characteristics Data BOREAS TF-01 SSA-OA Tower Flux, Meteorological, and Soil Temperature Data BOREAS TF-01 SSA-OA Understory Flux, Meteorological, and Soil Temperature Data BOREAS TF-09 SSA-OBS Tower Flux, Meteorological, and Soil Temperature Data 2. Investigator(s) 2.1 Investigator(s) Name and Title Gerry den Hartog Atmospheric Environment Service Harold Neumann Air Quality Processes Research Division Atmospheric Environment Service 2.2 Title of Investigation Boreal Forest Atmosphere Interactions: Exchanges of Energy, Water Vapor and Trace Gases (SSA-OA) 2.3 Contact Information Contact 1: Harold Neumann Air Quality Processes Research Division Atmospheric Environment Service Downsview, ON Canada (416) 739-4858 (416) 739-4224 (fax) hneumann@ec.gc.ca Contact 2: Robert Mickle Air Quality Processes Research Division Atmospheric Environment Service Downsview, ON Canada bob.mickle@ec.gc.ca Contact 3: Ralf Staebler Air Quality Processes Research Division Atmospheric Environment Service Downsview, ON Canada ralf.staebler@ec.gc.ca Contact 4: 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 Note: Equations and special characters are visible only in the MSWord version of this document. Measurements of the fluxes of momentum, sensible heat, water vapor, and CO2 were made with the eddy covariance technique. Velocity components, air temperature, water vapor density, and CO2 concentration in the air were sampled rapidly, and calculations of relevant covariances were performed from these samples to obtain the fluxes. For example, the flux of CO2 was determined as follows: where is the departure of the vertical velocity component from its mean over the averaging interval, usually 30 minutes, and is the departure of CO2 concentration from its mean. At the overstory level, three rotations in the coordinate transformation are applied to the flux data to make the lateral component ( ), vertical component ( ), and covariance ( ) of the wind vector equal to zero. At the understory level, however, only the mean lateral wind velocity component was rotated to zero under the suspicion that nonzero mean vertical velocities are possible within the trunk space. Webb, Pearman, and Leuning (1980) (WPL) corrections were made to the water vapor and carbon dioxide fluxes measured using the closed-path LI-COR 6262 IRGA. Broadening correction was done, but not on-line (see Chen et al., 1998, for summary of theory). 4. Equipment 4.1 Sensor/Instrument Description 4.1.1 Collection Environment Measurements were collected from beginning of the year to mid-September of 1994. Over that time period, temperature conditions from less than -30 °C to over 30 °C were experienced. 4.1.2 Source/Platform A 37-m walk-up scaffold main tower and a 6-m scaffold tower about 40 m from the main tower. Rain gauges were located in a small clearing 70 m NE of the main tower. 4.1.3 Source/Platform Mission Objectives The objective of the flux tower was to support instrumentation for the study of the fluxes of CO2, energy, water vapor, and momentum between the forest and atmosphere at the SSA-OA. 4.1.4 Key Variables Variables measured using eddy covariance: CO2 and water vapor fluxes, momentum fluxes, sensible heat fluxes, and latent heat fluxes. Supporting meteorological variables: net radiation, downward solar radiation, incident and reflected PPFD, wind speed, wind direction, air temperature, and precipitation. 4.1.5 Principles of Operation A sonic anemometer determines the wind speed by a pair of transducers acting alternately as transmitters and receivers, sending pulses of high-frequency ultrasound between themselves. The 3-D sonic has three pairs of transducers arranged in nonparallel axes. The LI-COR 6262 CO2/H2O analyzer is based on the difference in absorption of infrared radiation passing through two gas sampling cells. The reference cell is used for a gas of known CO2 or H2O concentration, and the sample cell is used for a gas of unknown concentration. Infrared radiation is transmitted through both cell paths, and the output of the analyzer is proportional to the difference in absorption between the two. The principles of operation of most of the supporting instruments can be found in Pearcy et al. (1991) and Fritschen and Gay (1979). 4.1.6 Sensor/Instrument Measurement Geometry Above-canopy sensors were supported by a vertical triangular mast mounted on top of a 37-m-tall scaffold-type main tower. Air temperature profiles were measured using aspirated resistance bulb thermometers at 0.8, 2.3, 6.8, 9.9, 13.0, 16.1, 19.2, 22.3, 25.4, 30.1, and 34.6 m above ground level. All thermometers were mounted on the main tower except for the 0.8 and 2.3 m heights, which were on a minitower 8 m WSW of the main tower. Vapor pressure and dewpoint profiles were measured using two water vapor instruments connected to the sampling system, a chilled mirror dewpoint hygrometer and an IRGA. Measurements were collected at 0.8, 2.3, 9.9, 16.1, 19.2, 22.3, 25.4, and 34.6 m above ground level, with all sampling locations on the main tower except for 0.8 and 2.3 m heights, which were on the minitower. The same sampling heights were used for the CO2 concentration profiles. 3-D sonic anemometers were operated at 39.5, 28.6, 18.6, 5.9 (all TR-61B probes), and 0.5 m (miniature probe) to provide profiles of energy, water vapor, and CO2 fluxes. Rain gauges were located in a small clearing 70 m NE of the main tower. Wind speed and direction were measured with a vane propeller anemometer mounted on the tower at 39.4 m height. Above-canopy air temperature and relative humidity were measured at 37.3 m height. The atmospheric pressure sensor was located in instrument hut B. Incident shortwave radiation was measured at 39.4 m height, mounted above the SW corner of the tower. Incident PPFD was measured at 38.8 m mounted 1 m out from the SW corner of the tower, and the reflected PPFD was measured at 38.7 m, just below the incident PPFD sensor. The two net radiometers were mounted side-by-side at end of a boom arm 4.5 m to SSW of the SW corner of the tower at 38.5 m height. The IR thermometer measuring canopy surface temperature was mounted at 27.4 m viewing canopy to NNE at an angle of 30°. Above-canopy dewpoint was measured with a dewpoint hygrometer at 39.5 m. Above-canopy CO2 concentration was measured at 34.6 m. Above-canopy ozone concentration was measured at 37.4 m, and the below canopy ozone concentration was sampled just outside instrument hut B at 3 m. 4.1.7 Manufacturer of Sensor/Instrument DAT-310 sonic anemometer: Kaijo-Denki Co., Ltd. No 19.1 Chrome Kanda-Nishikicho Chiyoda-Ku Tokyo 101 Japan LI-COR LI-6262 IRGA, 190-SB PPFD, and LAI-2000 PCA: LI-COR, Inc. P.O. Box 4425/4421 Superior Street Lincoln, NE 68504 (303) 499-1701 (303) 499-1767 (fax) KH2O krypton hygrometer: Campbell Scientific P.O. Box 551 Logan, UT 84321 CN-1 net radiometer: Middleton Instruments, Inc. P.O. Box 442 South Melbourne Victoria, 3205 Australia S-1 net radiometer: Swissteco Instruments Inc. Stegweg, Eichenwies, CH-94633 OBERRIET SG Switzerland PSP pyranometer and PIR pyrgeometer: The Eppley Laboratory, Inc. 12 Shefield Ave. P.O. Box 419 Newport, RI 02840 (401) 847-1020 (401) 847-1031 (fax) 05031 vane propeller anemometer: R.M. Young Co. Traverse City, MI Distributor: Campbell Scientific P.O. Box 551, Logan, UT 84321 (801) 753-234 (801) 752-3268 4000 IR thermometer: Everest Interscience, Inc. P.O. Box 3640 Fullerton, CA 92634-3640 (714) 992-4461 M1 dewpoint hygrometer (with D2 sensor): General Eastern Instruments Corp. Watertown, MA HMP-35C Vaisala humidity sensor: Vaisala, Inc. Woburn, MA Distributor: Campbell Scientific P.O. Box 551 Logan UT 84321 (801) 753-2342 (801) 752-3268 (fax) CS105 Barometer: Vaisala, Inc. Woburn, MA Distributor: Campbell Scientific P.O. Box 551 Logan, UT 84321 (801) 753-2342 (801) 752-3268 (fax) TE525 Tipping-bucket rain gauge: Texas Electronics Distributor: Campbell Scientific P.O. Box 551 Logan, UT 84321 (801) 753-2342 (801) 752-3268 (fax) Weighing rain gauge: Belfort Instrument Co. 1600 S. Clinton Street Baltimore, MD 21224 21x, CR10 Data logging system: Campbell Scientific P.O. Box 551, Logan, UT 84321 (801) 753-2342 (801) 752-3268 (fax) TD-4X2N diaphragm pump: Brailsford Co. 670 Milton Road Rye, NY 10580 (914) 967-1820 (914) 967-1836 (fax) DOA-V191-AA diaphragm pump: Gast, Inc. P.O. Box 97 Benton Harbor, MI (616) 926-6171 (616) 925-8288 (fax) Bev-a-line tube: Thermoplastic Processes, Inc. Sterling NS Dekoron tubing: Wirex Controls Ltd. 9446 McLaughlin Road N. Unit #27 Brampton, ON Canada, L6X 4H9 (905) 459-0742 (905) 450-8216 4.2 Calibration 4.2.1 Specifications Zeroing and calibration was done manually on the IRGA. Calibration was done using 350 ppm CO2 cylinders (Medigas) calibrated using AES cylinders and a LI- COR dewpoint generator. The two net radiometers were intercompared. The comparison yielded NET_RAD_ABV_CNPY_2 = 1.111*NET_RAD_ABV_CNPY_1 for net radiation values greater than 0 and NET_RAD_ABV_CNPY_2 = 1.224*NET_RAD_ABV_CNPY_1 net radiation values less than 0. TF-01 checked net radiometer calibration against a precision pyranometer by shading on 11-Apr-1994 at 17:30 to 18:30 Greenwich Mean Time (GMT); the change in NET_RAD_ABV_CNPY_2 was 3.1% greater than for the standard. 4.2.1.1 Tolerance The tipping bucket gauge had a resolution of 0.45 mm. 4.2.2 Frequency of Calibration Not given. 4.2.3 Other Calibration Information None. 5. Data Acquisition Methods The overstory eddy correlation system consisted of a 3-D sonic anemometer (model DAT-310 with model TR-61B probe, Kaijo-Denki, Tokyo, Japan) with a 20-cm path length, a model 6262 IRGA, and an ozone sensor. Air was drawn at 6.5 l min-1 down 6-m-long heated 3.2-mm i.d. Bev-a-line sampling tubing, then pumped through the sample cell using two diaphragm pumps (model TD-4X2N, Brailsford Co. Rye, NY) connected in parallel. To prevent condensation, the sampling tubing was heated (2-3 ºC above ambient) by passing an electric current through 20-AWG nichrome wire (about 15 ohms resistance) coiled around the exterior of the tubing. Sample cell pressure was approximately atmospheric pressure, and the delay time was 1.2 s. The IRGA was operated in differential mode with 320 mmol mol-1 CO2 in dry air flowing through the reference cell at 30 cm3 min-1. All raw data were recorded using PC systems with backup tape drives. Half-hour fluxes were calculated online. 6. Observations 6.1 Data Notes CO2 concentration, vapor pressure, and dewpoint profiles were collected from 03- Feb to 19-Sep-1994. Air temperature profiles were collected from 01-Feb to 19- Sep-1994. Daily precipitation data, the total of a 24-hour period ending at 15:00 GMT, were collected from 31-Jan to 19-Sep-1994. Tipping bucket gauge precipitation data were collected from 16-May to 29-Jul-1994. Above-canopy air temperature, wind speed and direction, relative humidity, dewpoint, incident shortwave radiation, incident PPFD, ozone concentration, and air pressure data begin on 01-Jan-1994. Net radiation begins 04-Feb-1994, reflected PPFD begins 19-July-1994, canopy surface temperature begins 18-Feb- 1994, above-canopy CO2 concentration begins 03-Feb-1994, and below-canopy ozone concentration begins 25-May-1994. All end 19-Sep-1994. Flux data were collected at the following heights: 39.5 m, above canopy; 28.6 m, above canopy; 18.6 m, within crown space, no water vapor or CO2 fluxes at this height; 5.85 m, above understory; 1.8 m, at top of understory, no water vapor or CO2 fluxes at this height; 0.45 m, within understory. Flux data at 39.5 m were collected from 02-Feb to 19-Sep-1994, at 28.6 m from 12-Feb to 19-Sep-1994, at 18.6 m from 09-Aug to 19-Sep-1994, at 5.85 m from 03- Apr to 19-Sep-1994, at 1.8 m from 19-May to 16-June-1994, and at 0.45 m from 16- June to 19-Sep-1994. Water vapor and CO2 flux data at 39.5 m were collected from 02-Feb to 19-Sep-1994, at 28.6 m from 10-June to 16-June-1994, at 5.85 m from 10-Aug to 22-Aug-1994, and at 0.45 m from 16-June to 19-Sep-1994 except for the period from 10-Aug to 22-Aug-1994. Coordinate transforms to set mean v and w wind vectors to zero were applied to the 39.5- and 28.6-m data; for data from the other heights, the coordinate transform applied set only mean v wind vector to zero. 6.2 Field Notes None. 7. Data Description 7.1 Spatial Characteristics 7.1.1 Spatial Coverage All data were collected at the BOREAS SSA-OA site in the Prince Albert National Park (PANP). North American Datum of 1983 (NAD83) coordinates for the site are latitude 53.62889° N, longitude 106.19779° W, and elevation of 600.63 m. 7.1.2 Spatial Coverage Map Not applicable. 7.1.3 Spatial Resolution Although the eddy covariance measurement is made at one point, it is well known that the fluxes measured with this technique can represent fluxes averaged over a relatively large area. An analysis of the upwind land surface area that contributes to a scalar flux measurement, often referred to as "fetch" or "footprint," is crucial in understanding the origins of the flux and any possible influences of spatial heterogeneity. According to Blanken's (1997) results (using Schuepp et al., 1990, model), the cumulative flux at 39 m reached 80% of the total flux at an upwind distance of 1,200 m under neutral conditions, 900 m under typical daytime stability conditions, and 2,700 m under typical nighttime stability conditions. The corresponding values for the 4-m height (above the understory) were 130, 80, and 300 m. Baldocchi (1997) suggests the latter values are overestimates. . From the above results, there was adequate fetch at the OA site because the forest extended for at least 3 km in all directions. 7.1.4 Projection None. 7.1.5 Grid Description None. 7.2 Temporal Characteristics 7.2.1 Temporal Coverage Different instruments came online at different times, so the periods of available data vary with instruments. CO2 concentration, vapor pressure, and dewpoint profiles were collected from 03-Feb to 19-Sep-1994. Air temperature profiles were collected from 01-Feb to 19-Sep-1994. Daily precipitation data were collected from 31-Jan to 19-Sep-1994. Tipping bucket gauge precipitation data were collected from 16-May to 29-Jul-1994. Above-canopy air temperature, wind speed and direction, relative humidity, dewpoint, incident shortwave radiation, incident PPFD, ozone concentration, and air pressure data begin on 01-Jan-1994. Net radiation began 04-Feb-1994, reflected PPFD began 19-July-1994, canopy surface temperature began 18-Feb-1994, above-canopy CO2 concentration began 03-Feb-1994, and below-canopy ozone concentration began 25-May-1994. All end 19-Sep-1994. Note that Saskatchewan Research Council (SRC) (Airborne Fluxes and Meteorology (AFM)-07) operated a MESONET site at the OA (70 m southeast of main tower) through the study period. Flux data at 39.5 m were collected from 0 2-Feb to 19-Sep-1994, at 28.6 m from 12-Feb to 19-Sep-1994, at 18.6 m from 09-Aug to 19-Sep-1994, at 5.85 m from 03- Apr to 19-Sep-1994, at 1.8 m from 19-May to 16-June-1994, and at 0.45 m from 16- June to 19-Sep-1994. Water vapor and CO2 flux data at 39.5 m were collected from 02-Feb to 19-Sep-1994, at 28.6 m from 10-June to 16-June-1994, at 5.85 m from 10-Aug to 22-Aug-1994, and at 0.45 m from 16-June to 19-Sep-1994 except for the period from 10-Aug to 22-Aug-1994. 7.2.2 Temporal Coverage Map None. 7.2.3 Temporal Resolution The data reported in the tower flux data are 30-minute statistical mean values. Daily precipitation data is the total of a 24-hour period ending at 15:00 GMT. 7.3 Data Characteristics Data characteristics are defined in the companion data definition file (tf02tflx.def). 7.4 Sample Data Record Sample data format shown in the companion data definition file (tf02tflx.def). 8. Data Organization 8.1 Data Granularity All of the TF-02 SSA-OA Tower Flux, Meteorological, and Precipitation Data are contained in one dataset. 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 (tf02tflx.def). 9. Data Manipulations 9.1 Formulae 9.1.1 Derivation Techniques and Algorithms There are many equations and formulae used in the calculations of fluxes from the raw voltage signals. Readers are referred to the relevant references for details. 9.2 Data Processing Sequence 9.2.1 Processing Steps Averages, variances, and covariances are calculated in real time, and coordinate rotation is applied on the half-hourly covariances and variances. Vapor pressure was calculated from dewpoint temperature using equations from Buck (1981). BORIS staff processed these data by: 1) Reviewing the initial data files and loading them online for BOREAS team access. 2) Designing relational data base tables to inventory and store the data. 3) Loading the data into the relational data base tables. 4) Working with the team to document the data set. 5) Extracting the data into logical files. 9.2.2 Processing Changes Above-canopy dewpoint temperature was measured with dewpoint hygrometer, except for the period 01-Jan to 01-Feb when it was calculated from relative humidity and air temperature. 9.3 Calculations 9.3.1 Special Corrections/Adjustments Sensible heat flux was derived from temperature from the sonic anemometer corrected for wind and humidity effects. Latent heat and water vapor fluxes were determined from closed path sensor with no density corrections applied. The CO2 flux was from the closed path sensor included corrections for water vapor flux. The standard deviation of wind direction from the sonic anemometers was computed using the Yamartino algorithm. The virtual heat flux was calculated from the virtual temperature as measured by the sonic anemometer, and corrected for wind effects. The standard deviation of air temperature and virtual temperature from the sonic anemometer were corrected for wind and humidity effects. The storage fluxes for latent heat and CO2 were calculated from differences of water vapor profiles and CO2 profiles, respectively, for the runs before and after the current run. The storage fluxes could be added to the latent heat flux or CO2 flux. However, this assumes no horizontal advection below the measurement height. The validity of this assumption is difficult to evaluate, and obvious problems occur after frontal passages. 9.3.2 Calculated Variables The above-canopy absolute humidity was calculated from air temperature and dewpoint temperature. Air density was computed from air temperature for air pressure = 94.5 kPa. The stability index was calculated using virtual temperature from the sonic anemometer. 9.4 Graphs and Plots None. 10. Errors 10.1 Sources of Error None given. 10.2 Quality Assessment 10.2.1 Data Validation by Source Outliers were removed from the data. The two net radiometers were intercompared. The comparison yielded NET_RAD_ABV_CNPY_2 = 1.111*NET_RAD_ABV_CNPY_1 for net radiation values greater than 0 and NET_RAD_ABV_CNPY_2 = 1.224*NET_RAD_ABV_CNPY_1 net radiation values less than 0. Net radiometer calibration was checked by TF-01 group against a precision pyranometer by shading on 11-Apr-1994 at 17:30 to 18:30 GMT; change in NET_RAD_ABV_CNPY_2 was 3.1% greater than for the standard. 10.2.2 Confidence Level/Accuracy Judgment None given. 10.2.3 Measurement Error for Parameters None given. 10.2.4 Additional Quality Assessments The Belfort rain gauge tended to lag in registering precipitation events, and occasionally produced spurious readings. The standard rain gauge was probably the most reliable of the precipitation measurements. 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 None given. 11.2 Known Problems with the Data None given. 11.3 Usage Guidance None given. 11.4 Other Relevant Information None. 12. Application of the Data Set These data are useful for the study of water, energy, and carbon exchange in a mature aspen forest. 13. Future Modifications and Plans Data collection from the SSA-OA tower continued after 1996. Contact Dr. T.A. Black for information about these data. 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 These data are available on the BOREAS CD-ROM series. Raw (20 Hz) data are available on CD-ROM by special request on a cost-recovery basis directly from the TF-02 team. 17. References 17.1 Platform/Sensor/Instrument/Data Processing Documentation None. 17.2 Journal Articles and Study Reports Baldocchi, D.D. 1997. Flux footprints within and over forest canopy. Boundary- Layer Meteorology, 85, 273-292. Black T.A., G. den Hartog, H.H. Neumann, P.D. Blanken, P.C. Yang, C. Russell, and Z. Nesic. 1996. Annual cycle of water vapor and carbon dioxide fluxes in and above a boreal aspen forest. Global Change Biology, 2, 101-111. Blanken, P.D. 1997. Evaporation within and above a boreal aspen forest. Ph.D. Thesis of UBC , 79-84. Buck. 1981. J. Appl. Meteorol. 20:1527-1532. Chen, W.J., T.A. Black, P.C. Yang, A.G. Barr, H.H. Neumann, Z. Nesic, P.D. Blanken, M.D. Novak, J. Eley, R.J. Ketler, and R. Cuenca. 1998. Effects of climatic variability on the annual carbon sequestration by a boreal aspen forest. Global Change Biology (in press). Fritschen, L.J. and L.W. Gay. 1979. Environmental Instrumentation. Springer- Verlag, Berlin, New York and Heidelberg. Fuchs, M. and C.B. Tanner. 1968. Calibration and field tests of soil heat flux plates. Soil Science Society of America Proceedings, 32, 326-328. Hook, W.R. and N.J. Livingston. 1996. Errors in converting time domain reflectometry measurements of propagation velocity to estimated of soil water content. Soil Sci. Soc. Amer. J., 59, 35-41. Kaimal, J.C. and J.E. Gaynor. 1991. Another look at sonic thermometry. Boundary- Layer Meteorology, 56, 401-410. Lee X., T.A. Black, and M.D. Novak. 1994. Comparison of flux measurements with open-and closed-path gas analyzers above an agricultural field and a forest floor. Boundary-Layer Meteorology, 67, 1995-202. Leuning R. and K.M. King. 1992. Comparison of eddy covariance measurements of CO2 fluxes by open- and closed-path CO2 analyzers. Boundary-Layer Meteorology, 59, 297-311. 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. 2000. Collected Data of The Boreal Ecosystem-Atmosphere Study. NASA. CD- ROM. Pearcy, R.W., J. Ehleringer, H.A. Mooney, and P.W. Rundel. 1991. Plant physiological ecology: Field methods and instrumentation. Chapman and Hall, London and New York. Schuepp P.H., M.Y. Leclerc, J.I. MacPerson, and R.L. Desjardins. 1990. Footprint prediction of scalar fluxes from analytical solutions of the diffusion equation. Boundary-Layer Meteorology, 50, 355-373. Sellers, P. and F. Hall. 1994. Boreal Ecosystem-Atmosphere Study: Experiment Plan. Version 1994-3.0, NASA BOREAS Report (EXPLAN 94). Sellers, P. and F. Hall. 1996. Boreal Ecosystem-Atmosphere Study: Experiment Plan. Version 1996-2.0, NASA BOREAS Report (EXPLAN 96). Sellers, P., F. Hall, and K.F. Huemmrich. 1996. Boreal Ecosystem-Atmosphere Study: 1994 Operations. NASA BOREAS Report (OPS DOC 94). Sellers, P., F. Hall, and K.F. Huemmrich. 1997. Boreal Ecosystem-Atmosphere Study: 1996 Operations. NASA BOREAS Report (OPS DOC 96). Sellers, P., F. Hall, H. Margolis, B. Kelly, D. Baldocchi, G. den Hartog, J. Cihlar, M.G. Ryan, B. Goodison, P. Crill, K.J. Ranson, D. Lettenmaier, and D.E. Wickland. 1995. The boreal ecosystem-atmosphere study (BOREAS): an overview and early results from the 1994 field year. Bulletin of the American Meteorological Society. 76(9):1549-1577. 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): 28,731-28,770. Webb, E.K., G.I. Pearman, and R. Leuning. 1980. Correction of flux measurements for density effects due to heat and water vapor transfer. Quarterly Journal of the Royal Meteorological Society, 106, 85-100. Yang, P.C. 1998. Carbon dioxide flux within and above a boreal aspen forest. Ph.D. thesis, University of British Columbia, Vancouver, Canada. 17.3 Archive/DBMS Usage Documentation None. 18. Glossary of Terms None. 19. List Of Acronyms AES - Atmospheric Environment Service AFM - Airborne Fluxes and Meteorology ASCII - American Standard Code for Information Interchange ATD - Atmospheric Technology Division ATI - Applied Technologies, Inc. BOREAS - BOReal Ecosystem-Atmosphere Study BORIS - BOREAS Information System CD-ROM - Compact Disk-Read-Only Memory DAAC - Distributed Active Archive Center EOS - Earth Observing System EOSDIS - EOS Data and Information System GIS - Geographic Information System GMT - Greenwich Mean Time GSFC - Goddard Space Flight Center HTML - Hyper-text Markup Language i.d. - inner diameter IFC - Intensive Field Campaign IR - Infrared IRGA - Infrared Gas Analyzer LAI - Leaf Area Index NAD83 - North American Datum of 1983 NASA - National Aeronautics and Space Administration NEP - Net Ecosystem Productivity NSA - Northern Study Area OA - Old Aspen ORNL - Oak Ridge National Laboratory PANP - Prince Albert National Park PAR - Photosynthetically Active Radiation PC - Personal Computer PPFD - Photosynthetic Photon Flux Density SRC - Saskatchewan Research Council SSA - Southern Study Area TDR - Time Domain Reflectometry TF - Tower Flux UBC - University of British Columbia URL - Uniform Resource Locator WPL - Webb, Pearman, and Leuning 20. Document Information 20.1 Document Revision Date Written: 09-Sep-1999 Last Updated: 20-Sep-1999 20.2 Document Review Date(s) BORIS Review: Science Review: 20.3 Document ID 20.4 Citation When using these data, please include the following acknowledgment as well as citations of relevant papers in Section 17.2: Data were collected and processed by G. den Hartog and H.H. Neumann of Atmospheric Environment Service. If using data from the BOREAS CD-ROM series, also reference the data as: den Hartog, G., R.E. Mickie, H.H. Neumann, and N.B.A. Trivett, "AES Flux Tower Measurements for BOREAS: Exchange of Energy, Water Vapor, and Trace Gases Project." 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 Keywords: Air Temperature Aspen Carbon Dioxide Concentration Carbon Dioxide Flux Latent Heat Flux Meteorology Momentum Flux Net Radiation PAR Photosynthetic Photon Flux Density Photosynthetically Active Radiation PPFD Rainfall Sensible Heat Flux Soil Heat Flux Soil Temperature Soil Water Potential Tower Flux Vapor Pressure Wind Speed TF02_Flux.doc 09/30/99