BOREAS TE-12 Incoming PAR Through the Forest Canopy Data Summary The BOREAS TE-12 team collected PAR data sets in support of its efforts to characterize and interpret information on shoot geometry, leaf optical properties, leaf water potential, and leaf gas exchange. The data were collected at the SSA-OBS site from 04-Jul-1996 to 25-Jul-1996. The data are stored 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 TE-12 Incoming PAR Through the Forest Canopy Data 1.2 Data Set Introduction The Terrestrial Ecology (TE)-12 team took measurements of incoming photosynthetically active radiation (PAR) as part of the BOReal Ecosystem- Atmosphere Study (BOREAS) at the Old Black Spruce (OBS) site in the Southern Study Area (SSA) from 04-Jul-1996 to 25-Jul-1996. PAR, in units of micro Einsteins per meter squared per second, from 0.4 to 0.7 microns, was measured in an array below the tree canopy, but above the understory. Ten LI-COR quantum sensors measured PAR, and minute averages are reported. 1.3 Objectives/Purpose The objective of this research was to characterize the duration and magnitude of sun flecks under a boreal forest canopy. 1.4 Summary of Parameters Minute averages of PAR, in units of micro Einstein per meter squared per minute. 1.5 Discussion TE-12 took measurements of incoming PAR at SSA-OBS from 04-Jul-1996 to 25-Jul- 1996. PAR, in units of micro Einsteins per meter squared per second, from 0.4 to 0.7 microns, was measured in an array below the tree canopy, but above the understory. Ten LI-COR quantum sensors measured PAR, and minute averages are reported. 1.6 Related Data Sets TE-12 Shoot Geometry Data TE-12 Leaf Gas Exchange Data 2. Investigator(s) 2.1 Investigators Name and Title Elizabeth A. Walter-Shea, Assoc. Professor 2.2 Title of Investigation Radiation and Gas Exchange of Canopy Elements in a Boreal Forest 2.3 Contact Information Contact 1: Mark A. Mesarch University of Nebraska Lincoln, NE (402) 472-5904 (402) 472-0284 (402) 472-6614 (fax) mmesarch1@unl.edu Contact 2: Elizabeth A. Walter-Shea University of Nebraska Lincoln, NE (402) 472-1553 (402) 472-6614 (fax) ewalter-shea1@unl.edu Contact 3: Andrea Papagno Raytheon ITSS NASA GSFC Greenbelt, MD (301) 286-3134 (301) 286-0239 (fax) Andrea.Papagno@gsfc.nasa.gov 3. Theory of Measurements Fluxes need to be measured at understory levels to relate to environmental and state variables and explain the stand scale fluxes. At the understory level, upper canopy elements shade the understory partially, creating sun flecks. These sun flecks fluctuate over time, both spatially and in intensity. An array of hemisphere sensors was placed above the understory to measure a represented area of transmitted PAR. The time frame of the measurements, 1-minute averages, provided a time scale representative of a plant's photosynthetic processes' reaction time. 4. Equipment 4.1 Sensor/Instrument Description A LI-COR Quantum Sensor (LI-190SA) was used to detect sun flecks. A silicon photo diode with an enhanced response in the visible wavelengths was used to measure PAR, from 0.4 to 0.7 microns. A visible bandpass interference filter, in combination with color glass filters, was mounted in a cosine corrected head. Error calculations indicated that under sun-and-sky radiation, and under various natural or artificial light sources, the relative measurement errors are less than 5.0%. Therefore, this sensor can be used within or inverted over canopies and in greenhouses, controlled growth chambers, and confined laboratory conditions. Generally, this instrument measures hemispherical incoming radiation; however, when placed within a canopy, the instrument acts as a point source detector. The quantum sensors were placed in an array surrounding a central point at varying distances from this central point. The table below describes the directions and distances from the central point for sensor. Sensor serial number Direction Distance (m) Q15566 North 15 Q9020 Northeast 16 Q15565 East 10 Q2738 East-Southeast 2.5 Q9123 Southeast 12 Q9022 South 12 Q7433 South-Southwest 1.7 Q7434 Southwest 5 Q10890 West 12 Q89085 Northwest 4.5 4.1.1 Collection Environment Measurements were made onsite at the OBS-SSA site. 4.1.2 Source/Platform Each LI-COR quantum sensor was attached to a LI-COR 2003S Mounting and Leveling Fixture. These fixtures are made of anodized aluminum with stainless steel leveling screws and a weatherproof spirit level. The fixture was attached to a wood block that was attached to the top of a pole, 0.6 m above the sphagnum surface. Once the wood block was attached to the pole the leveling screws on the fixture were used to level the fixture holding the quantum sensor. 4.1.3 Source/Platform Mission Objectives None given. 4.1.4 Key Variables Incoming PAR under a tree canopy. 4.1.5 Principles of Operation The LI-COR quantum sensor uses a silicon diode to convert sunlight to electrical energy (voltage). 4.1.6 Sensor/Instrument Measurement Geometry The quantum sensors were placed in an array surrounding a central point at varying distances from this central point. The table below describes the directions and distances from the central point for sensor. Sensor serial number Direction Distance (m) Q15566 North 15 Q9020 Northeast 16 Q15565 East 10 Q2738 East-Southeast 2.5 Q9123 Southeast 12 Q9022 South 12 Q7433 South-Southwest 1.7 Q7434 Southwest 5 Q10890 West 12 Q89085 Northwest 4.5 Each LI-COR quantum sensor was attached to a LI-COR 2003S Mounting and Leveling Fixture. These fixtures are made of anodized aluminum with stainless steel leveling screws and a weatherproof spirit level. The fixture was attached to a wood block that was attached to the top of a pole 0.6 m above the sphagnum surface. Once the wood block was attached to the pole, the leveling screws on the fixture were used to level the fixture holding the quantum sensor. 4.1.7 Manufacturer of Sensor/Instrument LI-COR, Inc. Box 4425 Lincoln, NE 68504 (402) 467-3576 4.2 Calibration 4.2.1 Specifications None given. 4.2.1.1 Tolerance None given. 4.2.2 Frequency of Calibration LI-COR quantum sensors were calibrated at the manufacturer in May 1996. 4.2.3 Other Calibration Information Calibration coefficients for the sensors were in units of micro Einsteins per meter squared per second per millivolt. Sensor number Serial Number Coefficient 1 Q9020 -253.54 2 Q9022 -282.05 3 Q7434 -252.00 4 Q9123 -308.31 5 Q15566 -311.21 6 Q15565 -245.64 7 Q89085 -285.45 8 Q10890 -286.44 9 Q7433 -200.00 10 Q2734 -194.55 5. Data Acquisition Methods The quantum sensors were placed in an array surrounding a central point at varying distances from this central point. The sensors were placed in the array to cover an area of approximately 600 m2, which was representative of an area of understory under the canopy. The table below describes the directions and distances from the central point for sensor. Sensor serial number Direction Distance (m) Q15566 North 15 Q9020 Northeast 16 Q15565 East 10 Q2738 East-Southeast 2.5 Q9123 Southeast 12 Q9022 South 12 Q7433 South-Southwest 1.7 Q7434 Southwest 5 Q10890 West 12 Q89085 Northwest 4.5 Each LI-COR quantum sensor was attached to a LI-COR 2003S Mounting and Leveling Fixture. These fixtures are made of anodized aluminum with stainless steel leveling screws and a weatherproof spirit level. The fixture was attached to a wood block that was attached to the top of a pole, 0.6 m above the sphagnum surface. Once the wood block was attached to the pole the leveling screws on the fixture were used to level the fixture holding the quantum sensor. Data were measured every 5 seconds and reported as 1-minute averages. 6. Observations 6.1 Data Notes None given. 6.2 Field Notes None given. 7. Data Description 7.1 Spatial Characteristics 7.1.1 Spatial Coverage The SSA measurement site and its associated North American Datum of 1983 (NAD83) coordinates are: SSA-OBS, site id G8I4T, Lat/Long: 53.98717°N, 105.11779°W, Universal Transverse Mercator (UTM) Zone 13, N: 5,982,100.5, E: 492,276.5. 7.1.2 Spatial Coverage Map Not applicable. 7.1.3 Spatial Resolution The maximum distance between any two quantum sensors was 27 meters. The entire array covered approximately 600 m2. 7.1.4 Projection Not applicable. 7.1.5 Grid Description Not applicable. 7.2 Temporal Characteristics 7.2.1 Temporal Coverage Data were collected at the OBS-SSA site From 04-Jul-1996 to 25-Jul-1996 7.2.2 Temporal Coverage Map Not available. 7.2.3 Temporal Resolution Data were collected on most days from sunrise to sunset (approximately 4 a.m. to 10 p.m. local time). Measurements were made every 5 seconds and reported as 1- minute averages. 7.3 Data Characteristics Data characteristics are defined in the companion data definition file (te12parc.def). 7.4 Sample Data Record Sample data format shown in the companion data definition file (te12parc.def). 8. Data Organization 8.1 Data Granularity All of the incoming PAR through the forest canopy data are contained in one dataset. 8.2 Data Format(s) The data file 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 (te12parc.def). 9. Data Manipulations 9.1 Formulae None. 9.1.1 Derivation Techniques and Algorithms Not applicable. 9.2 Data Processing Sequence None given. 9.2.1 Processing Steps None given. 9.2.2 Processing Changes None given. 9.3 Calculations 9.3.1 Special Corrections/Adjustments None given. 9.3.2 Calculated Variables None given. 9.4 Graphs and Plots None given. 10. Errors 10.1 Sources of Error The manufacturer estimates that the LI-COR quantum sensor will measure within +/- 5.0 percent relative error of the true incoming PAR. 10.2 Quality Assessment 10.2.1 Data Validation by Source None given. 10.2.2 Confidence Level/Accuracy Judgment None given. 10.2.3 Measurement Error for Parameters None given. 10.2.4 Additional Quality Assessments None given. 10.2.5 Data Verification by Data Center Data were examined for general consistency and clarity. 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 given. 12. Application of the Data Set This data set can be used to study the incoming PAR of the boreal forest. 13. Future Modifications and Plans None given. 14. Software 14.1 Software Description None given. 14.2 Software Access None given. 15. Data Access 15.1 Contact for Data Center/Data Access Information These BOREAS data are available from the Earth Observing System Data and Information System (EOS-DIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The BOREAS contact at ORNL is: ORNL DAAC User Services Oak Ridge National Laboratory (865) 241-3952 ornldaac@ornl.gov ornl@eos.nasa.gov 15.2 Procedures for Obtaining Data BOREAS data may be obtained through the ORNL DAAC World Wide Web site at http://www-eosdis.ornl.gov/ or users may place requests for data by telephone, electronic mail, or fax. 15.3 Output Products and Availability Requested data can be provided electronically on the ORNL DAAC's anonymous FTP site or on various media including, CD-ROMs, 8-MM tapes, or diskettes. The complete set of BOREAS data CD-ROMs, entitled "Collected Data of the Boreal Ecosystem-Atmosphere Study", edited by Newcomer, J., et al., NASA, 1999, are also available. 16. Output Products and Availability 16.1 Tape Products None given. 16.2 Film Products None given. 16.3 Other Products These data are available on the BOREAS CD-ROM series. 17. References 17.1 Platform/Sensor/Instrument/Data Processing Documentation LI-COR Radiation Sensors. 1991. Pub. No. 8609-56. LI-COR, Inc., Lincoln, NE. 17.2 Journal Articles and Study Reports 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 (OPSDOC 94). Sellers, P., F. Hall, and K.F. Huemmrich. 1997. Boreal Ecosystem-Atmosphere Study: 1996 Operations. NASA BOREAS Report (OPSDOC 96). Sellers, P.J., 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. Bull. Am. Meteorol. Soc. 76:1549-1577. 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), 28,731-28,769. 17.3 Archive/DBMS Usage Documentation None. 18. Glossary of Terms None. 19. List of Acronyms ASCII - American Standard Code for Information Interchange BOREAS - BOReal Ecosystem-Atmosphere Study BORIS - BOREAS Information System CD-ROM - Compact Disk-Read-Only Memory DAAC - Distributed Active Archive Center DOY - Julian Day of Year EOS - Earth Observing System EOSDIS - EOS Data and Information System GMT - Greenwich Mean Time GSFC - Goddard Space Flight Center HTML - HyperText Markup Language IFC - Intensive Field Campaign MIX - Mixed Wood NAD83 - North American Datum of 1983 NASA - National Aeronautics and Space Administration NOAA - National Oceanic and Atmospheric Administration NSA - Northern Study Area OA - Old Aspen OBS - Old Black Spruce ORNL - Oak Ridge National Laboratory PANP - Prince Albert National Park PAR - Photosynthetically Active Radiation RSS - Remote Sensing Science SSA - Southern Study Area TE - Terrestrial Ecology TF - Tower Flux URL - Uniform Resource Locator UTM - Universal Transverse Mercator 20. Document Information 20.1 Document Revision Date Written: 06-Jan-1999 Last Updated: 28-Apr-1999 20.2 Document Review Date(s) BORIS Review: 11-Mar-1999 Science Review: 20.3 Document ID 20.4 Citation E.A. Walter-Shea and M.A. Mesarch, both of UNL. 20.5 Document Curator 20.6 Document URL Keywords Below Canopy Boreal Forest PAR Quantum Sensor Sun Fleck TE12_Canopy_PAR.doc 06/09/99