BOREAS HYD-08 Gross Precipitation Data Summary The BOREAS HYD-08 team made measurements of surface hydrological processes at the SSA-OBS Tower Flux site 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 gross precipitation measurements for July to August 1996. Gross precipitation is the precipitation that falls that is not intercepted by tree canopies. 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 at the SSA-OBS Tower Flux site 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 gross precipitation measurements for July to August 1996. Gross precipitation is the precipitation that falls that is not intercepted by tree canopies. These data are stored in ASCII text files. 1.1 Data Set Identification BOREAS HYD-08 1996 Gross Precipitation Data 1.2 Data Set Introduction This particular data set contains the gross precipitation measurements from the BOReal Ecosystem-Atmosphere Study (BOREAS) Hydrology (HYD)-08 team at the Southern Study Area (SSA) Old Black Spruce (OBS) for July to August 1996. 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 as 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. Gross precipitation was measured to permit future parameterization of flux models. 1.4 Summary of Parameters Gross Precipitation (after storm events) (millimeters of H20). 1.5 Discussion Hydrological processes such as canopy evaporation and moss storage and evaporation may play a significant role in controlling water fluxes during the growing season in boreal wetlands. Canopy interception and moss storages and 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 1996 Moss Lysimeter Measurements BOREAS HYD-08 1996 Moss Dry Weights BOREAS HYD-08 1996 Throughfall Measurements BOREAS HYD-08 1994 Moss Lysimeter Weight Measurements 2. Investigator(s) 2.1 Investigator(s) Name and Title Dr. Lawrence Band University of Toronto 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 --------- David Knapp Raytheon STX Corporation NASA GSFC Greenbelt, MD (301) 286-1424 (301) 286-0239 (fax) David.Knapp@gsfc.nasa.gov 3. Theory of Measurements Two shielded catch buckets were located in clearings parallel to the transect of measurement plots but within 100 m of a transect near the SSA-OBS site. The clearings were selected to provide at least a 45 degree unobstructed vertical cone. The bucket was placed in a pit so that the orifice was just above the surrounding surface vegetation (mosses and sedges). The reservoir was manually drained of water once a day and after every rain event; care was taken to shake loose any drops on the inside surface of the reservoir. The drained water was weighed on an electronic balance at a leveled location. 4. Equipment 4.1 Sensor/Instrument Description Each bucket consisted of a catch funnel mounted on a reservoir. The catch funnel had a 10-cm by 10-cm vertical lip followed by a 10-cm cone to prevent splashing of rain drops outside the cone and wind turbulence evaporating water collected on the cone surface. The reservoir was a closed 2-liter metal container with an orifice to receive the catch funnel drainage at the top and a drain plug at the base. 4.1.1 Collection Environment These data were collected in a clearing surrounded by trees. 4.1.2 Source/Platform Gross Precipitation Gauges - Placed in pits in clearings within 100 m of transect of turf lysimeter sites. 4.1.3 Source/Platform Mission Objectives The objective was to measure gross precipitation after rain events. 4.1.4 Key Variables Gross precipitation. 4.1.5 Principles of Operation The gauges were designed to hold an amount of water that fell as precipitation. The amount of water was weighed and the weights were used to determine the water equivalent depth. 4.1.6 Sensor/Instrument Measurement Geometry None given. 4.1.7 Manufacturer of Sensor/Instrument Gauges - 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 effects 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 Weight Scales Weight < 1 kg: accurate to +/- 0.1 g Weight > 1 kg: accurate to +/- 1.0 g 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 was placed at a randomly selected location in each stratified plot. The locations were not changed during the field campaign. Measurements were made at each plot for all gauges before moving to another plot. The measurements were made by weighing the amount of water in the gauge. These weights were converted to water depths based on the orifice area of the gauge. 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 gross precipitation gauge was located within 500 meters of the SSA-OBS flux tower along a single transect leading radially outwards from the tower. The location of the flux tower was determined by Global Positioning System (GPS) and is at the following coordinates: BOREAS Grid Site Longitude Latitude X Y SSA-OBS (Flux Twr.) 105.11779W 53.98717N 385.012 348.646 7.1.2 Spatial Coverage Map None. 7.1.3 Spatial Resolution These data represent point measurements, although they may represent the gross precipitation over a larger area based on the “fetch” of the location of the gauge. The “fetch” of a rain gauge depends on wind speed, precipitation intensity, and the cover over the gauge. 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 from July to August 1996 with some small gaps. 7.2.2 Temporal Coverage Map Not applicable. 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. The amount of precipitation recorded is the amount that fell since the gauge was last checked. 7.3 Data Characteristics Data characteristics are defined in the companion data definition file (h08gp96.def). 7.4 Sample Data Record Sample data format shown in the companion data definition file (h08gp96.def). 8. Data Organization 8.1 Data Granularity All of the BOREAS HYD-08 Gross Precipitation 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 (h08gp96.def). 9. Data Manipulations 9.1 Formulae See Section 9.1.1. 9.1.1 Derivation Techniques and Algorithms The computation of water equivalent depth for gauges was performed using: d (mm) = 1000 (mm/m) * mass_water(g) / ( 1000kg/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 to compute 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 the 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 Error Gross precipitation gauge errors - Some water drops remain on the sides and funnel of the gauge. The weight of these drops was less than 1 g as determined by comparing the weight of the dry gauge to the weight of the gauge after decanting. This suggests an error of -1 g. Unquantifiable Error Errors caused by wind turbulence around the gauge, evaporation from the collector funnel, or condensation on the funnel are possible. It is likely that precipitation is underestimated because of evaporation from the funnel. 10.2 Quality Assessment 10.2.1 Data Validation by Source These data are preliminary. General trends in the data are reliable; however, individual measurements may be in error. 10.2.2 Confidence Level/Accuracy Judgment Mean values or 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 Estimates of errors of each measurement variable are given below. Time: +/-2 hours Gross Precipitation - The accuracy of the gross precipitation measurements is thought to be approximately 10%. The precision of each measurement is directly related to the precision of the scale that weighed the gauge, as well as other factors. 10.2.4 Additional Quality Assessments Data quality assessment by the investigator is continuing. 10.2.5 Data Verification by Data Center Data that were loaded into the data tables were spot checked against the original ASCII data to check for errors that occurred when the data were loaded. 11. Notes 11.1 Limitations of the Data Isolated data points may be in error because of improper recording or reformatting during documentation. These data are still being reviewed by the investigators. 11.2 Known Problems with the Data The time specified for data entries may not be precise (i.e., within an hour or two of actual time). 11.3 Usage Guidance 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 The HYD-08 data sets can be used for: 1. Quantifying rough canopy interception rates for given storm size at the SSA- OBS. 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 by the investigators is continuing. 14. Software 14.1 Software Description None. 14.2 Software Access None. 15. Data Access 15.1 Contact Information Ms. Beth Nelson BOREAS Information System NASA Goddard Space Flight Center 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 HYD-08 gross precipitation 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 None given. 17.1 Platform/Sensor/Instrument/Data Processing Documentation None. 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. 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 GPS - Global Positioning System GSFC - Goddard Space Flight Center HYD - Hydrology IFC - Intense Field Campaign NASA - National Aeronautics and Space Administration NSA - Northern Study Area OBS - Old Black Spruce Site ORNL - Oak Ridge National Laboratory PANP - Prince Albert National Laboratory 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: 24-Jul-1998 Science Review: 31-Jul-1998 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 publishing results that are based on these data. 20.5 Document Curator 20.6 Document URL KEYWORDS PRECIPITATION MOSS HYD08_GrossPrecip.doc 08/20/98