BOREAS HYD-08 1996 Gravimetric Moss Moisture Data Summary The BOREAS HYD-08 team made measurements of surface hydrological processes that were collected at the SSA-OBS Tower Flux site in 1996 to support its research into point hydrological processes and the spatial variation of these processes. Data collected may be useful in characterizing canopy interception, drip, throughfall, moss interception, drainage, evaporation, and capacity during the growing season at daily temporal resolution. This particular data set contains the gravimetric moss moisture measurements from July to August 1996. To collect these data, a nested spatial sampling plan was implemented to support research into spatial variations of the measured hydrological processes and ultimately the impact of these variations on modeled carbon and water budgets. These data are stored in ASCII text 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 The BOREAS HYD-08 team made measurements of surface hydrological processes that were collected at the SSA-OBS Tower Flux site in 1996 to support its research into point hydrological processes and the spatial variation of these processes. Data collected may be useful in characterizing canopy interception, drip, throughfall, moss interception, drainage, evaporation, and capacity during the growing season at daily temporal resolution. This particular data set contains the gravimetric moss moisture measurements from July to August 1996. To collect these data, a nested spatial sampling plan was implemented to support research into spatial variations of the measured hydrological processes and ultimately the impact of these variations on modeled carbon and water budgets. These data are stored in ASCII text files. 1.1 Data Set Identification BOREAS HYD-08 1996 Gravimetric Moss Moisture Data 1.2 Data Set Introduction This particular data set contains the gravimetric moss moisture measurements made at the BOReal Ecosystem-Atmosphere Study (BOREAS) Southern Study Area (SSA) Old Black Spruce (OBS) from July to August 1996. To collect these data, a nested spatial sampling plan was implemented to support research into spatial variations of the measured hydrological processes and ultimately the impact of these variations on modeled carbon and water budgets. These data are stored in American Standard Code for Information Interchange (ASCII) text files. 1.3 Objective/Purpose The objective of the data set was to quantify the magnitude and spatial variation of storages and fluxes at the moss surface and during precipitation events in a selected Picea Mariana stand. The following parameters were measured to permit future parameterization of flux models: throughfall, stemflow, moss water storage, and gross precipitation. A nested spatial sampling plan was implemented to characterize the length scales of variations of the measured parameters for future use in modeling studies and for comparison with measurements at the flux tower located at the SSA-OBS study site. 1.4 Summary of Parameters Turf Lysimeter Dry Weights Turf Lysimeter Water Equivalent Depths (daily and after storm events) (mm H20) 1.5 Discussion Hydrological processes such as canopy evaporation, moss storage, and moss evaporation may play a significant role in controlling water fluxes during the growing season in boreal wetlands. Canopy interception, moss storage, and moss evaporation were measured using mass balance methods (throughfall catch buckets and lysimeters) to give a quantitative estimate of these processes for sparse black spruce stands. More importantly, the spatial sampling scheme allowed quantification of the expected variation of these processes within the footprint of a colocated flux measurement tower. This will allow consideration of the sub-tower-footprint controls on vapor fluxes that the tower is measuring. In addition, the data set will be useful in parameterizing flux models for the site targeted as well as determining the typical variation in fine scale processes that the models may have to account for when scaling to watershed and regional extents. 1.6 Related Data Sets BOREAS HYD-08 1994 and 1996 Throughfall Data BOREAS HYD-08 1994 Gravimetric Moss Moisture Data BOREAS HYD-08 1996 Gross Precipitation Data 2. Investigator(s) 2.1 Investigator(s) Name and Title Dr. Lawrence Band University of Toronto Department of Geography Toronto, Ontario 2.2 Title of Investigation Simulation of Boreal Ecosystem Carbon and Water Budgets: Scaling from Local to Regional Extents 2.3 Contact Information Contact 1 --------- Richard Fernandes University of Toronto Toronto, Ontario (416) 978-5070 (416) 978-6729 (fax) fernande@geog.utoronto.ca Contact 2 --------- Dr. Lawrence Band University of Toronto Toronto, Ontario (416) 978-3375 (416) 978-6729 (fax) lband@geog.utoronto.ca Contact 3 --------- David Knapp Raytheon STX Corporation NASA GSFC Code 923 Greenbelt, MD 20771 (301) 286-1424 (301) 286-0239 (fax) David.Knapp@gsfc.nasa.gov 3. Theory of Measurements Turf Lysimeters Turfs were located randomly; however, some turfs were relocated because of the presence of live roots. Turfs 15 cm x 15 cm square were extracted by hand to the bottom of the live moss layer (defined by the presence of a horizontal litter mat for Pleurozium scheberi. and by the end of thalli for Sphagnum spp.). The turfs were placed on a mesh tray and then replaced in the pit from which they were extracted. Turfs were weighed daily and after rain events by placing them directly on a leveled electronic scale. If turfs were over field capacity (water dripped from them), the phenomenon was noted, and weighing proceeded after the majority of drip water had ceased. Any large litter components that appeared on turfs during the measurement period were removed and placed on the moss surface beside the turf. Turf water equivalent depth was computed by later oven drying the turfs and determining dry turf + lysimeter tray weights to compute water weight, assuming a constant 1000 kg/m3 density of H20 to compute water equivalent depth. 4. Equipment 4.1 Sensor/Instrument Description Turf Lysimeter Mesh Base A 15 cm x 15 cm aluminum mesh tray with 10 gauge wire mesh and 1 cm mesh holes was used as the base of each lysimeter. Monofilament fishing line was used to form handles to extract the lysimeter from the turf pit. Electronic Weigh Scales An electronic balance was used for weighing quantities with weights less than 1 kg. A different balance was used for weighing quantities above 1 kg. Both balances were tared before and after weighing and had been calibrated immediately before the field campaign and at the University of Toronto after the measurement campaign. The balances had an auto off condition where taring was not possible or when battery power was low. 4.1.1 Collection Environment These measurements were made in a spruce forest, near the SSA-OBS tower site, where moss covered the ground. 4.1.2 Source/Platform Turf Lysimeters - Placed in pits from which turfs were extracted. 4.1.3 Source/Platform Mission Objectives The objective was to measure daily changes in water storages or turf weights. 4.1.4 Key Variables Turf Lysimeter - Turf weight, turf water equivalent depth. 4.1.5 Principles of Operation All of the equipment depended on holding a quantity of H20 and turf which was then weighed. The weight of the water was determined by subtracting the oven- dried weight of each turf from the weights that were measured in the field under wet conditions. The weight of the water can then be converted to a water equivalent depth based on the size of the gauge (15 cm by 15 cm). 4.1.6 Sensor/Instrument Measurement Geometry All throughfall and catch gauges were repositioned using a bubble level to ensure that they were upright. The turf lysimeters were extracted vertically from the pits even for pits on the sides of hummocks. 4.1.7 Manufacturer of Sensor/Instrument Gauges and Lysimeters - Darryl Carlysle Moses and Kira Dunham (University of Toronto, Dept. of Geography) Weigh Scales - (2) MARS MS3000W Series. 4.2 Calibration The weigh scales were calibrated to within the manufacturer's specifications immediately before the measurement campaign and at the University of Toronto after the campaign. The effect of the weigh scales being off level were also tested with no appreciable difference for tilt angles less than 20 degrees (which were defined by the first indent in the bubble level gauge used in the field). 4.2.1 Specifications None given. 4.2.1.1 Tolerance None given. 4.2.2 Frequency of Calibration The weigh scales were calibrated to within the manufacturer's specifications immediately before the measurement campaign and at the University of Toronto after the campaign. 4.2.3 Other Calibration Information None. 5. Data Acquisition Methods Each gauge and lysimeter was placed at a randomly selected location in each stratified plot or in clearings in the case of throughfall gauges. The locations were not changed during the field campaign. Measurements were made at each plot for all gauges and lysimeters before moving to another plot. 6. Observations 6.1 Data Notes None given. 6.2 Field Notes None given. 7. Data Description 7.1 Spatial Characteristics All measurement plots were located within 500 m of the SSA-OBS flux tower along a single transect leading radially outwards from the tower. The goal was to place the plots on a perceived wetness gradient while keeping them within the flux tower footprint. In addition, each plot was located so it was separated from the others to characterize the typical spatial variability of surface hydrological processes. Unfortunately, no plot was located in a region dominated by Sphagnum bogs, so turf lysimeters with sphagnum were located in isolated sphagnum patches within 10 m of each plot. 7.1.1 Spatial Coverage Seven plots were located along a transect in the vicinity of the SSA-OBS flux tower. Each plot had five live turf lysimeters (identified as gauges L1 through L5) and five throughfall gauges (in a separate data set), one throughfall gauge near each live turf lysimeter, three live + fermentation layer turf lysimeters (identified as gauges LF1 through LF3), and one nearby sphagnum turf lysimeter (identified as gauge SP1). In addition, two throughfall plots with over 20 throughfall gauges were located independently (in a separate data set). 7.1.2 Spatial Coverage Map None given. 7.1.3 Spatial Resolution The resolution to which the measurement applies varies according to the type of measurement. Turf lysimeters measure weights for the extent of the turf (15 cm x 15 cm surface, approximately 15 cm deep). However, the throughfall gauges may catch precipitation from a region larger than their orifices. The "fetch" of a throughfall or rain gauge depends on wind speed, precipitation intensity, and the cover over the gauge. 7.1.4 Projection Measurement locations within sites are represented on sketches with no projection. 7.1.5 Grid Description Not applicable. 7.2 Temporal Characteristics 7.2.1 Temporal Coverage The data were collected from July to August 1996 with some small gaps. 7.2.2 Temporal Coverage Map None. 7.2.3 Temporal Resolution Data were collected daily and after each rain event where possible. The time of day of data collection is indicated in the data record. However, it typically took 1.5 hours to complete data collection of all sites. 7.3 Data Characteristics Data characteristics are defined in the companion data definition file (h08gm96.def). 7.4 Sample Data Record Sample data format shown in the companion data definition file (h08gm96.def). 8. Data Organization 8.1 Data Granularity All of the BOREAS HYD-08 1996 Gravimetric Moss Moisture Data are contained in one dataset. 8.2 Data Format(s) A data record consists of a series of numerical and character fields of American Standard Code for Information Interchange (ASCII) characters of varying length. The fields are separated by commas with the character fields enclosed in single apostrophe marks. Sample data records are shown in the companion data definition file (h08gm96.def). 9. Data Manipulations 9.1 Formulae See Section 9.1.1. 9.1.1 Derivation Techniques and Algorithms The mass of water in a lysimeter was estimated as: mass_water(g) = wet_mass(g) - dry_mass(g) - tray_mass(g) The computation of water equivalent depth for the lysimeters was performed using: d (mm) = 1000 (mm/m) * mass_water(g) / ( 1000 kg/m3 * area_gauge_bottom(m2) ) 9.2 Data Processing Sequence 9.2.1 Processing Steps 1) Set up necessary equipment. 2) Performed daily weighings and emptied weighed gauges. 3) Performed the necessary data manipulations and computed water equivalent depth. 4) Added the necessary column headings. 5) Transferred the information to the BOREAS Information System (BORIS). 6) BORIS Staff loaded the data into its relational data base. 9.2.2 Processing Changes None. 9.3 Calculations See Section 9.1.1. 9.3.1 Special Corrections/Adjustments None. 9.3.2 Calculated Variables None. 9.4 Graphs and Plots None. 10. Errors 10.1 Sources of Error Quantifiable Errors 1) Location errors - The plots were located with reference to the flux tower using dead reckoning. Errors on the order of +/- 10 m can be expected for the location of plot origins and +/- 0.1 m for the location of measurement sites within plots. 2) Dimensional measurements - Measurements of radii and length and width dimensions were made using a metric hand ruler. An error of +/-0.5 mm in precision is possible. This will result in negligible errors in computed surface areas of catch gauges or turf trays. 3) Area of moss turfs - While the turf tray area was measured accurately and with high precision, the actual turf did not always have the same area as the tray because of a sloping surface or bulging sides. This may result in a difference in actual area of +/-5% of the computed area. 4) Throughfall gauge weighing error - Tests were performed to detect the weight of water drops present on sides of throughfall gauges. These weights were not measurable. The average weight of all throughfall gauges was used to compute the net weight of water in the gauge. The error in using the average weight is less than +/-0.1 g and can be considered negligible. 5) Weigh scale errors - The weigh scale errors assuming no contamination of the weighing surface (e.g., water drops on it) are given by the manufacturer as a precision error of +/-0.1 g for weights less than 1000 g and +/-1.0 g for weights between 1,000 g and 10,000 g. Unquantifiable Errors Moss Turfs - Changes in mass balance caused by the addition or removal of litter by natural processes (wind, runoff, decomposition, animals). - Drainage of water during extraction of the turf for weighing (the concept of field capacity in mosses is ill-defined). - Lack of root uptake in the turf layer (this is likely only a factor for LF turfs as there are few roots in live layers of mosses which are active in uptake). - Lack of connection between moss turf and pit surroundings (especially significant for capillary rise, which is common in sphagnum moss turfs) 10.2 Quality Assessment These data are preliminary. General trends in the data are reliable; however, individual measurements may be completely in error. 10.2.1 Data Validation by Source None. 10.2.2 Confidence Level/Accuracy Judgment Mean values of plots and gross precipitation accuracy is estimated at approximately 2 out of 5, individual measurements at 1 out of 5. 10.2.3 Measurement Error for Parameters The time of the measurement is accurate to +/- 2 hours. The measurement error of the weights of the moss turfs is given in Section 10.1. The water equivalent depth is related to these weight errors, but the precision and accuracy of the water equivalent depths are not quantified in this document. 10.2.4 Additional Quality Assessments Data quality assessment is ongoing. 10.2.5 Data Verification by Data Center The data were received from the Hydrology (HYD)-08 science team and loaded into the BORIS relational data base. After loading, the data were compared with the original data files to make sure that they were loaded properly. 11. Notes Isolated data points may be in complete error because of improper recording or reformatting during documentation. Revision of data is continuing. 11.1 Limitations of the Data None given. 11.2 Known Problems with the Data None given. 11.3 Usage Guidance The moss water fluxes are conservative. Any strong jumps in time series should be flagged as potential measurement or recording errors unless explained by commensurate inputs. 11.4 Other Relevant Information None. 12. Application of the Data Set This data set can be used for: 1. Quantifying rough canopy interception rates for given storm size at the SSA- OBS site. 2. Quantifying daily moisture fluxes in moss layers. 3. Possibly inferring relationships between stand parameters and measured fluxes. 4. Parameterizing flux models (especially hydrological models at stand to local scale). 13. Future Modifications and Plans Data quality assessment is ongoing by the investigators. 14. Software 14.1 Software Description Not applicable. 14.2 Software Access Not applicable. 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, fax, or electronic mail. 15.4 Data Center Status/Plans The HYD-08 1996 moss gravimetric 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 (865) 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 ASCII text files. 17. References 17.1 Platform/Sensor/Instrument/Data Processing Documentation None given. 17.2 Journal Articles and Study Reports Haddeland, I. and D.P. Lettenmaier. 1995. Hydrologic Modeling of Boreal Forest Ecosystems. Water Resources Series Technical Report No. 143. University of Washington, 123 pp. Price, A.G., K. Dunham, T. Carleton, and L.E. Band. 1997. Variability of water fluxes through the Black Spruce (Picea Mariana) canopy and Feather Moss (Pleurozium Schreberi) carpet in the Boreal Forest of Northern Manitoba. Journal of Hydrology, 196, 310-323. 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, BOREAS Special Issue, 102(D24), Dec. 1997, pp. 28731-28770. 17.3 Archive/DBMS Usage Documentation None given. 18. Glossary of Terms None given. 19. List of Acronyms ASCII - American Standard Code for Information Interchange BOREAS - BOReal Ecosystem-Atmosphere Study BORIS - BOREAS Information System CD-ROM - Compact Disk (optical), Read-Only Memory DAAC - Distributed Active Archive Center EOS - Earth Observing System EOSDIS - EOS Data and Information System FFC-T - Focused Field Campaign - Thaw GMT - Greenwich Mean Time GSFC - Goddard Space Flight Center HYD - Hydrology IFC - Intensive Field Campaign NASA - National Aeronautics and Space Administration NSA - Northern Study Area OBS - Old Black Spruce ORNL - Oak Ridge National Laboratory PANP - Prince Albert National Park SSA - Southern Study Area URL - Uniform Resource Locator 20. Document Information 20.1 Document Revision Date Written: 20-Nov-1996 Revised: 04-Aug-1998 20.2 Document Review Date(s) BORIS Review: 15-Jul-1998 Science Review: 20.3 Document ID 20.4 Citation This data product was collected and processed by the BOREAS Science Team HYD-08, led by Prof. Lawrence Band at the University of Toronto. Please contact the principal investigator, Dr. Lawrence Band, before publication of results that are based on these data. 20.5 Document Curator 20.6 Document URL KEYWORDS MOSS WATER EQUIVALENT DEPTH HYD08_MossGrav96.doc 08/20/98