BOREAS RSS-17 Stem, Soil, and Air Temperature Data Summary The BOREAS RSS-17 team collected several data sets in support of its research in monitoring and analyzing environmental and phenological states using radar data. This data set consists of tree bole and soil temperature measurements from various BOREAS flux tower sites. Temperatures were measured with thermistors implanted in the hydroconductive tissue of the trunks of several trees at each site and at various depths in the soil. Data were stored on a data logger at intervals of either 1 or 2 hours. The majority of the data were acquired between early 1994 and early 1995. The primary product of this data set is the diurnal stem temperature measurements acquired for selected trees at five BOREAS tower sites. The data are provided in tabular ASCII format. 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 RSS-17 Stem, Soil, and Air Temperature Data 1.2 Data Set Introduction This documentation file describes tree bole and soil temperature data acquired during the BOReal Ecosystem-Atmosphere Study (BOREAS) field experiment at five of the BOREAS tower sites. The tree bole data were collected in separate but representative trees at each of the tower sites. Data were collected from the Southern Study Area (SSA) at the Old Black Spruce (OBS), Old Jack Pine (OJP), Old Aspen (OA), and Young Jack Pine (YJP) sites. Data were also collected at the Northern Study Area NSA OBS site. The majority of the data were acquired between early 1994 and early 1995. All of the temperature data were collected with 3x3x1 mm thermistors. Data were post-processed to derive temperature values (in Celsius) from the raw data taken (in kOhms) by resistance measurements from nonlinear response-type thermistors. Thermistors were implanted in the hydroconductive tissues of selected tree trunks and at various depths in the soil. Measurements were recorded automatically on a data logger at 1 or 2 hour intervals. 1.3 Objective/Purpose These measurements were taken to assist with the interpretation of radar backscatter measurements obtained with the Earth Resource Satellite-1 (ERS-1) Synthetic Aperture Radar (SAR). Data were used to assess the freeze/thaw state of the soil and vegetation to aid interpretation of the radar images. 1.4 Summary of Parameters and Variables The primary measured parameter is diurnal vegetation temperature. Some soil and air temperatures were collected at a subset of sites. 1.5 Discussion Temperature measurements were used to quantify freeze/thaw transitions in the soil and vegetation. Landscape freeze/thaw transitions are readily observable with imaging radar. Thus, radar may be applied to assess growing season length in boreal landscapes. 1.6 Related Data Sets BOREAS RSS-17 Dielectric Constant Profile Measurements BOREAS RSS-17 Black Spruce Xylem Sap Flow Measurements at the SSA-OBS Site BOREAS RSS-17 1994 ERS-1 Level-1 Backscatter Change Images 2. Investigator(s) 2.1 Investigator(s) Name and Title Principal Investigator Dr. JoBea Way Scientist Co-Investigator Dr. Kyle McDonald Scientist Co-Investigator Dr. Reiner Zimmermann Scientist 2.2 Title of Investigation Monitoring Environmental and Phenologic State and Duration of State with SAR as Input to Improved C02 Flux Models 2.3 Contact Information Contact 1 --------- Dr. JoBea Way Jet Propulsion Laboratory California Institute of Technology Pasadena, CA USA (818) 354-8225 (818) 354-9476 (fax) way@lor.jpl.nasa. Contact 2 --------- Dr. Kyle McDonald Jet Propulsion Laboratory California Institute of Technology Pasadena, CA USA (818) 354-3263 (818) 354-9476 (fax) kyle.mcdonald@jpl.nasa.gov Contact 3 --------- Dr. Reiner Zimmermann Bayreuth Institute for Terrestrial Ecosystem Research (BITOEK) Plant Ecology II University of Bayreuth Germany +49-921-555624 +49-921-555799 (fax) reiner.zimmermann@bitoek.uni-bayreuth.de Contact 4 ------------- Jaime Nickeson Raytheon STX Corporation NASA GSFC Greenbelt, MD (301) 286-3373 (301) 286-0239 (fax) Jaime.Nickeson@gsfc.nasa.gov 3. Theory of Measurements Thermistor sensors are variable resistors that change their electrical resistance to a direct current (DC) in a predictable manner depending on the ambient temperature. This study used Siemens-841-3K type thermistors that have a nonlinear decrease of resistance with increasing temperature and a negligible hysteresis. The small resistor size ensures a fast response to temperature changes in the measured environment (tree boles/soil/air). The temperature response of each sensor is better than the desired temperature resolution of 0.25°C. Temperatures were calculated from the measured resistance and a conversion algorithm. The algorithm was derived using the manufacturer's resistance-temperature conversion table. Sensor response was checked under controlled temperature conditions against 1) table values for electrical resistance and 2) calculated temperature values when using the conversion algorithm. Deviation of the calculated temperature from the manufacturer's temperature table was less than 0.2 degrees between -40 and +40°C. Approximately 8 to 12 trees were monitored at each installation to verify similar or uniform behavior of the freeze/thaw state of the tree trunks. 4. Equipment 4.1 Sensor/Instrument Description Thermistors were connected to stranded and insulated cables with a screen cover (computer signal cable type). 4.1.1 Collection Environment Soil temperatures were collected with capsuled soil thermistors inserted into holes drilled in the soil and then backfilled. Tree bole temperatures were collected using insulated thermistors that were inserted into 4 to 5 mm holes drilled into the tree boles. The holes were closed with silicone after insertion of the thermistor. 4.1.2 Source/Platform The tree temperature sensors were mounted directly in the trees being monitored. Soil sensors were inserted to depths between 5 cm and 50 cm, as noted in the data files. 4.1.3 Source/Platform Mission Objectives The objective of these measurements was to support interpretation of radar remote sensing observations, especially during the spring thaw and autumn freeze-up periods. 4.1.4 Key Variables The key variables being measured were stem, soil, and air temperatures. The measurements were converted to °C. 4.1.5 Principles of Operation Thermistor sensors are variable resistors that change their electrical resistance to a DC in a predictable manner depending on the ambient temperature. By monitoring the DC resistance of a thermistor, one may infer the ambient temperature in the medium surrounding the device. 4.1.6 Sensor/Instrument Measurement Geometry Thermistors were implanted in the tree trunks at appropriately 1.8 meters above the soil. Sensors were inserted to depths between 5 and 20 mm, as noted in the data files. Soil sensors were inserted to depths between 5 and 50 cm, as noted in the data files. Measurement accuracy of the thermistors was determined to be +/- 0.2°C, as based on laboratory testing. 4.1.7 Manufacturer of Sensor/Instrument Sensor units were constructed in the field at BOREAS. Thermistors were manufactured by Siemens, Germany, and are available from numerous U.S. electronic supply houses. The thermistor type was Siemens Heissleiter M841 / 3 K / a1. 4.2 Calibration 4.2.1 Calibration Specifications Temperature was calculated from the measured resistance and a conversion algorithm. The algorithm was based on the manufacturer's resistance-temperature conversion table. Sensor response was checked under controlled temperature conditions against 1) table values for electrical resistance and 2) calculated temperature values when using the conversion algorithm. Deviation of the calculated from the manufacturer's temperature table was less than 0.2 degrees between -40 and +40°C. 4.2.1.1 Tolerance None given. 4.2.2 Frequency of Calibration Further calibration of these instruments was not performed. 4.2.3 Other Calibration Information None given. 5. Data Acquisition Methods Soil temperatures were collected with capsuled soil thermistors inserted into holes drilled in the soil and then backfilled. Tree bole temperatures were collected using insulated thermistors that were inserted into 4 to 5 mm holes drilled into the tree boles. The holes were closed with silicone after insertion of the thermistor. Measurements were processed and stored with a Delta-T data logger (DL-2), which is manufactured in England. The time interval for the data storage varied during the observation period. Data were measured every minute and averaged by the logger for the indicated time interval. Data storage occurred at the end of the time interval averaged. A constant current source of 20 microAmpere provided by the logger was used to measure the DC resistance of each thermistor. Data were stored in the data logger and downloaded by laptop during site visits. 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 tree stem temperature data submitted to the BOREAS Information system (BORIS) were collected at five general sites: 1) NSA-OBS (NSA Old Black Spruce) 2) SSA-OBS (SSA Old Black Spruce) 3) SSA-OJP (SSA Old Jack Pine) 4) SSA-OA (SSA Old Aspen) 5) SSA-YJP (SSA Young Jack Pine) The stem temperature data were collected at every site visited, in a minimum of 4 and a maximum of 11 different trees. The number of trees from which stem temperature data were collected varied by site. The minimum numbers of trees measured was 4 and the maximum number of trees measured was 11. The air temperature data were measured at one location at each of two sites (SSA-OJP and SSA-OA). Air temperature measurements were not made at the three remaining sites. Soil temperature data were measured at three depths at the NSA-OBS site and at four depths at the SSA-YJP site. Soil temperature measurements were not made at the remaining three sites.” The North American Datum 1983 (NAD83) UTM coordinates for the sites are: Site UTM Zone UTM Northing UTM Easting stem soil air ------- -------- ------------ ----------- ---- ---- --- NSA-OBS 14 6192853.4 532444.5 x x SSA-YJP 13 5969762.5 523320.2 x x SSA-OJP 13 5974257.5 520227.7 x x SSA-OBS 13 5982100.5 492276.5 x SSA-OA 13 5942899.9 420790.5 x x 7.1.2 Spatial Coverage Map Not available. 7.1.3 Spatial Resolution The air, soil, and stem temperature measurements taken by Remote Sensing Science team 17 (RSS-17) are directly representative only of the medium into which the thermistors were inserted at the sites listed. 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 continuously collected over the various sites during the period from 25-Oct-1993 to 27-Apr-1995. A more detailed breakdown by site is given in section 7.2.2. 7.2.2 Temporal Coverage Map Site Dates of data collection ------- -------------------------- NSA-OBS 13-Apr-1994 to 30-Oct-1994 SSA-OBS 25-Oct-1993 to 27-Apr-1995 SSA-OA 16-Feb-1994 to 25-Apr-1995 SSA-OJP 19-Feb-1994 to 26-Apr-1995 SSA-YJP 15-Jul-1994 to 26-Apr-1995 7.2.3 Temporal Resolution The time interval between actual temperature measurements was 1 minute. These observations were then averaged over time periods ranging from 10 minutes to 1 hour. The averaged values are the temperatures given in the data files. 7.3 Data Characteristics Data characteristics are defined in the companion data definition file (rs7ssatd.def). 7.4 Sample Data Record Sample data format shown in the companion data definition file (rs7ssatd.def). 8. Data Organization 8.1 Data Granularity All of the BOREAS RSS-17 Stem, Soil, and Air Temperature Data are contained in one dataset. 8.2 Data Format(s) The data files on CD-ROM contain a series of numerical and character fields of varying length separated by commas. The character fields are enclosed within single apostrophe marks. There are no spaces between the fields. 9. Data Manipulations 9.1 Formulae None given. 9.2 Data Processing Sequence 9.2.1 Processing Steps Thermistor resistance was measured in kOhms and converted to °C using the manufacturer's data conversion table. 9.2.2 Processing Changes None given. 9.3 Calculations 9.3.1 Special Corrections/Adjustments None given. 9.3.2 Calculated Variables Thermistor resistance was measured in kOhms and converted to °C using the manufacturer's data conversion table. 9.4 Graphs and Plots None. 10. Errors 10.1 Sources of Error Thermistors may read higher temperatures than their environment when exposed to direct radiation or if output leads get shorted by moisture in cables with faulty insulation. The latter is a problem after rain if the shorting resistance is very high, and its effect is hard to separate/detect from true readings of sensor resistance. 10.2 Quality Assessment 10.2.1 Data Validation by Source None given. 10.2.2 Confidence Level/Accuracy Judgment Measurement accuracy of the thermistors was determined to be +/- 0.2 °C, as based on laboratory testing. 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 BOREAS staff performed initial quality checks while loading the data into BORIS. This was, by no means, an exhaustive effort. Individual users are cautioned that unreliable data may still be present. 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 NSA-OBS: One soil temperature sensor was also inserted to a depth of 700 mm below the surface but it was shorted during the season in 1994 by cable damage and thus not used in this data file. SSA-OASP: One stem temperature probe was also inserted at 10 mm into JP1, but the sensor readings were found to be erratic beginning in Sept. of 1994. Data collected after this date were removed. SSA-OBS: Four soil temperature sensors were also inserted to a depth of 50, 250, 450, and 700 mm below the surface, but they were shorted by sensor and cable damage during 1994 and thus the data were not included in this file. 12. Application of the Data Set Radar may be applied to assess growing season length in boreal landscapes. 13. Future Modifications and Plans No future modifications are planned. 14. Software 14.1 Software Description Data conversion performed in Sigmaplot 4.0 for DOS (Jandel Scientific, acquired by SPSS, Inc., http://www.spss.com/). 14.2 Software Access The software mentioned above may be acquired from SPSS, Inc. or a software reseller. 15. Data Access 15.1 Contact Information Ms. Beth Nelson BOREAS Data Manager NASA GSFC Greenbelt, MD (301) 286-4005 (301) 286-0239 (fax) Elizabeth.Nelson@.gsfc.nasa.gov 15.2 Data Center Identification See Section 15.1. 15.3 Procedures for Obtaining Data Users may place requests by telephone, electronic mail, or fax. 15.4 Data Center Status/Plans The RSS-17 stem, soil, and air temperature data are available from the Earth Observing System Data and Information System (EOSDIS), Oak Ridge National Laboratory (ORNL), Distributed Active Archive Center (DAAC). The BOREAS contact at ORNL is: ORNL DAAC User Services Oak Ridge National Laboratory Oak Ridge, TN (423) 241-3952 ornldaac@ornl.gov ornl@eos.nasa.gov 16. Output Products and Availability 16.1 Tape Products None. 16.2 Film Products None. 16.3 Other Products The data are available as tabular American Standard Code for Information Interchange (ASCII) files. 17. References 17.1 Platform/Sensor/Instrument/Data Processing Documentation None given. 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.and F. Hall. 1997. BOREAS Overview Paper. JGR Special Issue. 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 (JGR), BOREAS Special Issue, 102(D24), Dec. 1997, pp. 28731-28770. 17.3 Archive/DBMS Usage Documentation None. 18. Glossary of Terms None. 19. List of Acronyms ASCII - American Standard Code for Information Interchange BOREAS - BOReal Ecosystem-Atmosphere Study BORIS - BOREAS Information System DAAC - Distributed Active Archive Center DC - Direct Current EOS - Earth Observing System EOSDIS - EOS Data and Information System ERS-1 - Earth Resources Satellite-1 GSFC - Goddard Space Flight Center NASA - National Aeronautics and Space Administration NSA - Northern Study Area OA - Old Aspen OBS - Old Black Spruce OJP - Old Jack Pine ORNL - Oak Ridge National Laboratory PANP - Prince Albert National Park RSS - Remote Sensing Science SAR - Synthetic Aperture Radar SSA - Southern Study Area URL - Uniform Resource Locator (a World Wide Web address) UTM - Universal Transverse Mercator YJP - Young Jack Pine 20. Document Information 20.1 Document Revision Date(s) Written: 15-Jul-1997 Last Updated: 04-Aug-1998 20.2 Document Review Date(s) BORIS Review: 10-Jun-1998 Science Review: 20.3 Document ID None. 20.4 Citation Please acknowledge the efforts of the following investigators when using this dataset: R. Zimmermann, K. C. McDonald, J. B. Way. 20.5 Document Curator 20.6 Document URL Keywords: Stem temperature Air temperature Soil temperature RSS17_Stem_Temp 08/20/98