BOREAS HYD-03 Subcanopy Meteorological Measurements Summary The BOREAS HYD-03 team collected several data sets related to the hydrology of forested areas. This data set includes measurements of wind speed and direction; air temperature; relative humidity; and canopy, trunk, and snow surface temperatures within three forest types. The data were collected in the SSA-OJP (1994) and SSA-OBS and SSA-OA (1996). Measurements were taken for 3 days in 1994 and 4 days at each site in 1996. These measurements were intended to be short term to allow the relationship between subcanopy measurements and those collected above the forest canopy to be determined. The subcanopy estimates of wind speed were used in a snow melt model to help predict the timing of snow ablation. 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 HYD-03 Subcanopy Meteorological Measurements 1.2 Data Set Introduction This data set includes measurements of wind speed and direction within one aspen and two conifer forests. The data were collected in the BOReal Ecosystem- Atmosphere Study (BOREAS) Southern Study Area (SSA) Old Jack Pine (OJP) (1994) and the SSA-Old Black Spruce (OBS) and SSA-Old Aspen (OA) (1996). Measurements were taken for only 3 days in 1994 and 4 days at each site in 1996. An RM Young wind monitor, a Vaisala temperature and relative humidity (temp/RH) probe, and infrared thermometers were used to measure canopy, trunk, and snow surface temperatures. The wind monitor and temp/RH probe were mounted 2 meters above the snow surface, and a Campbell Scientific CR10 datalogger was used for all data collection. 1.3 Objective/Purpose This study was undertaken to predict spatial distributions of energy transfer and snow properties important to the hydrology, remote sensing signatures, and transmissivity of gases through the snow and their relation to forests in boreal ecosystems. The purpose of these measurements was to allow the relationship between subcanopy measurements and those collected above the forest canopy to be determined. Once they were determined, the above-canopy measurements were modified to estimate the subcanopy measurements. The subcanopy estimates of wind speed were used in the snow melt model to help predict the timing of snow ablation. 1.4 Summary of Parameters Parameters measured with respect to this documentation are canopy wind speed and direction, air temperature, relative humidity, stem temperature and snow surface temperature. 1.5 Discussion During the Focused Field Campaign-Winter (FFC-W) 1994 and 1996, meteorological parameters were measured at 2 m height in SSA-OJP (1994) and SSA-OBS and OA (1996). The data were collected for only 3 days (1994) or 4 days (1996) and are intended for comparison with above-canopy meteorological data. The data are averages of several measurements over a 10-min. (1994) and 1-min. (1996) interval. An RM Young wind monitor, a Vaisala temp/RH probe mounted 2 meters above the snow surface and a Campbell Scientific CR10 datalogger were used for data collection. Infrared thermometers were aimed at tree canopies, trunks and the snow surface to provide measurements. The sensors and the datalogger system are among the best available. Because of the nature of the forest canopy, wind speeds were VERY low, and in many cases below the threshold value of the sensor (1.0 m/s). For this reason, the data are somewhat questionable as to the absolute magnitude of the wind, but provide good relative information as to the timing and magnitude of wind events. The wind direction data are believed to be as accurate as the manufacturer's specifications. 1.6 Related Data Sets BOREAS TF-02 SSA-OA Tower Flux Data BOREAS TF-01 SSA-OA Tower Flux Data BOREAS TF-05 SSA-OJP Tower Flux Data BOREAS TF-09 SSA-OBS Tower Flux Data BOREAS HYD-03 Subcanopy Incoming Solar Radiation Measurements 2. Investigator(s) 2.1 Investigator(s) Name and Title Robert E. Davis Research Physical Scientist U.S. Army Cold Regions Research and Engineering Laboratory (CRREL) 2.2 Title of Investigation Distributed Energy Transfer Modeling in Snow and Soil for Boreal Ecosystems 2.3 Contact Information Contact 1 ------------ Janet P. Hardy U.S. Army CRREL Hanover, NH (603) 646-4306 (603) 646-4278 (fax) jhardy@crrel.usace.army.mil Contact 2 ----------- Dr. Robert E. Davis US Army CRREL 72 Lyme Road Hanover, NH (603) 646-4219 (603) 646-4278 (fax) bert@crrel.usace.army.mil Contact 3 ----------- David Knapp NASA GSFC Greenbelt, MD (301) 286-1424 (301) 286-0239 (fax) David.Knapp@gsfc.nasa.gov 3. Theory of Measurements The meteorological data were collected to investigate the effect of forest structure on the within-canopy winds, temperatures, and humidity. Data were compared with those collected from BOREAS flux towers at heights above the canopy to assist in developing a relationship between subcanopy and above-canopy winds in species of the boreal forest. This understanding is essential in modeling snow ablation in the forest. 4. Equipment 4.1 Sensor/Instrument Description 4.1.1 Collection Environment All data were collected during winter campaigns; therefore the instruments were subjected to cold temperatures. Days were relatively clear and cold, and forest winds were light during the collection period. Cold temperatures would not affect the sensors nor the data quality, but low wind speeds (below the 1.0 m/s threshold) affect the quality of wind data. 4.1.2 Source/Platform 2-meter tower in forest. 4.1.3 Source/Platform Mission Objectives To measure within-canopy winds, temperature, and humidity. 4.1.4 Key Variables Within Canopy: Wind speed and wind direction, air temperature, relative humidity, trunk and snow surface temperature. 4.1.5 Principles of Operation Wind Monitor: The wind monitor measures horizontal wind speed and direction. Propeller rotation produces an AC signal with frequency proportional to wind speed. The AC signal is monitored and data are processed by a Campbell datalogger. Wind direction is measured by applying constant voltage to a potentiometer and the output signal is an analog voltage directly proportional to azimuth angle. Temp/RH Probe: Sensors within the probe measure the air temperature and relative humidity according to specifications discussed below. Infrared Thermometers: An infrared thermometer measures radiant energy. Temperature readings are taken with an infrared thermometer by aiming the infrared temperature transducer at the desired object. The infrared thermometers used in this study have fields-of-view (FOV) of 15° and 4°. It was important in orienting the temperature sensor that the entire FOV was filled with the desired object. Infrared Radiometers: The Eppley Precision Infared Radiometer (PIR) (Pyrgeometer) measures incoming long-wave radiation of wavelengths between 4 µm and 50 µm. This instrument is believed to be the most accurate radiometer produced commercially for the measurement of long-wave radiation. The pyrgeometer measures the exchange of radiation between a horizontal blackened surface (i.e. the detector) and the target viewed (i.e. sky or ground). The signal is monitored and data are processed on a Campbell Scientific datalogger (CR10). 4.1.6 Sensor/Instrument Measurement Geometry Wind Monitor: This sensor was located on top of a tower, 2 meters above the snow surface. The sensor was oriented to true south in 1994 during installation, except in 1996, when the sensor was oriented to magnetic south. Temp/RH Probe: This sensor with radiation shield was mounted on the same tower approximately 2 m above the snow surface. Infrared Thermometer: The infrared thermometers used to measure canopy and trunk temperatures were mounted on tripods, approximately 1 m above the snow surface, and the sensor was pointed at the west or east side of the tree trunk. For infrared thermometers pointing at the canopy, care was taken to find a thick part of the canopy and to avoid measuring any background. The radiometer used for snow surface temperature measurements was similarly mounted on a tripod and aimed at the snow surface. Infrared Radiometers (pyrgeometers): Sensors were located on the snow surface using either a foam block (1994) or the radiometer case (1996) for support on the snow surface. Sensors were leveled daily using the bubble level mounted on the radiometer base. 4.1.7 Manufacturer of Sensor/Instrument Wind Monitor: Manufacturer: R.M. Young Company Distributor: Campbell Scientific Inc. 815 W. 1800 N. Logan, Utah 84321-1784 (801) 753-2342 Vaisala Temp/RH Probe, Model HMP35C: Manufacturer: Vaisala, Inc., Woburn, MA Distributor: Campbell Scientific, Inc. 815 W. 1800 N. Logan, UT 84321-1784 (801) 753-2342 Everest Series 4000 Infrared Temperature Transducer (low temperature model) Manufacturer: Everest Interscience, Inc. Everest Interscience, Inc. 1120 S. Raymond Fullerton, CA 92631 (800) 422-4342 Eppley Precision Infrared Radiometer (pyrgeometer) Manufacturer: Eppley Laboratory, Inc. 12 Sheffield Ave. Newport, RI 02840 (401) 847-1020 4.2 Calibration Wind Monitor: The sensor was oriented to true south during installation, except in 1996 when the sensor was oriented to magnetic south. A Brunton compass was used in the orientation of the sensor. This sensor is better oriented to the south because of a 5° "dead zone" between 355° and 360°. Temp/RH probe: Probes are calibrated to specifications of +/- 3% RH. Recalibration is performed at room temperature at 20%, 50%, and 85% RH. Infrared Thermometers: Infrared temperature transducers were calibrated by Everest upon purchase. Laboratory tests were conducted periodically for comparison of sensors and to provide confidence in the data. Infrared Radiometers (pyrgeometers): All pyranometers were new in 1994 and were therefore factory calibrated, with reference to Eppley primary standards, just prior to deployment in the field in 1994. 4.2.1 Specifications Wind Monitor: The RM Young sensor has a 5°, wind direction, "dead zone" between 355° and 360°. Temp/RH Probe: The probe is used only with a white radiation shield obtained from the distributor. Infrared Thermometers: Spectral pass-band = 8 ?m to 14 ?m. emmissivity preset at factory at 0.98. FOV = 4° and 15°. Operating distance = 0.2 m to 1,000 ft focus. Optical configuration = 35-mm precision corrected refractive optics. Infrared Radiometers (pyrgeometers): Sensitivity = 4 µVolts per Watt per meter2 Receiver: circular 1 cm2 in area. Linearity = +/- 1%, 0 to 700 Watts per m2 Cosine response = better than 5% from normalization, insignificant for a diffuse source. 4.2.1.1 Tolerance Wind Speed: Accuracy = +/- 0.3 m/s. Wind speed threshold sensitivity = 1.0 m/s (the wind speed data are not accurate below 1.0 m/s). Wind Direction: Accuracy = +/- 3.0° (<1%). Temp/RH probe: RH range = 0-100%. Temperature range: -35 °C to 50 °C. Accuracy at temperatures between -24°C and 48°C = <+/-0.1°C. Accuracy at temperature of -40°C = +/-0.5°C. Infrared thermometers: Temperature range = -25 °C to 75 °C. Accuracy = +/-0.5 °C. Resolution = +/- 0.1 °C. Infrared radiometers: Temperature dependance = +/- 2%, -20 °C to 40 °C. 4.2.2 Frequency of Calibration Wind Monitor: The RM Young wind sensor was fully calibrated when purchased on 19-Jan-1994 and has not been recalibrated since purchase. The RM Young manual provides details on calibrating the sensor. Temp/RH Probe: On a regular basis and prior to field use, several Vaisala Temp/RH probes are run adjacent to each other and concurrently to compare precision with other sensors. Probes that appear to be imprecise are either returned to the manufacturer for recalibration, or retired. Only probes with a high degree of precision are used in the field. This instrument was bought on 30-Jun-1994. Infrared Thermometers: Factory calibrated upon initial purchase. Infrared thermometer #1: bought in 1994. Infrared thermometer #2: bought in 1994. Infrared thermometer #3: bought in 1991, recalibrated 1992. Infrared thermometer #3 was returned to manufacturer 1 year after purchase to improve its cold weather handling and recalibrated, since it is an older model. Prior to field use we conducted laboratory tests using 0 °C ice baths to provide confidence in instrument. Infrared Radiometers (pyrgeometers): The manufacturer of the pyranometers recommends calibration after a cumulative use of 2 years. These radiometers were new at the beginning of the FFC-W 1994 and therefore are well within calibration. Because they have been used for only ~20 days per year and stored in their dark case when not in use, the calibration should be valid for several years at the current rate of usage. 4.2.3 Other Calibration Information Available from the manufacturer. 5. Data Acquisition Methods All sensors were installed according to manufacturer procedures. Data were recorded on a Campbell Scientific datalogger. The datalogger was programmed to measure parameters every minute and output 10-minute averages (1994) and measure parameters every second and output 1-minute averages (1996). 6. Observations 6.1 Data Notes None given. 6.2 Field Notes Wind direction oriented to true south in 1994. Wind direction oriented to magnetic south in 1996. 7. Data Description 7.1 Spatial Characteristics 7.1.1 Spatial Coverage Site Year Longitude Latitude ------------------------------------------------- SSA-OJP 1994 104.69203W 53.91634N SSA-OBS 1996 105.11779W 53.98718N SSA-OA 1996 106.19779W 53.6289N All measurements were made within 50 meters of flux tower sites. 7.1.2 Spatial Coverage Map Not available. 7.1.3 Spatial Resolution Point data, 2-meter height in forest. 7.1.4 Projection All latitude/longitude locations are given in the North American Datum of 1983 (NAD83). 7.1.5 Grid Description Not applicable. 7.2 Temporal Characteristics 7.2.1 Temporal Coverage FFC-W 1994: 06-10-Feb-1994 SSA-OJP: 06-10-Feb-1994 SSA-OBS: 28-Feb-03-Mar-1996 SSA-OA: 04-08-Mar-1996 7.2.2 Temporal Coverage Map SSA-OJP: 06-10-Feb-1994 SSA-OBS: 28-Feb-03-Mar-1996 SSA-OA: 04-08-Mar-1996 7.2.3 Temporal Resolution 10-minute averages (1994) 1-minute averages (1996) 7.3 Data Characteristics Data characteristics are defined in the companion data definition file (h3scmet.def). 7.4 Sample Data Record Sample data format shown in the companion data definition file (h3scmet.def). 8. Data Organization 8.1 Data Granularity All of the Subcanopy Meteorological Measurements Data are contained in one dataset. 8.2 Data Format(s) The data files contain numerical and character fields of varying length separated by commas. The character fields are enclosed with a single apostrophe marks. There are no spaces between the fields. Sample data records are shown in the companion data definition files (h3scmet.def). 9. Data Manipulations 9.1 Formulae Not applicable. 9.1.1 Derivation Techniques and Algorithms Not applicable. 9.2 Data Processing Sequence Not applicable. 9.2.1 Processing Steps Not applicable. 9.2.2 Processing Changes Not applicable. 9.3 Calculations 9.3.1 Special Corrections/Adjustments Infrared thermometer #3 did not provide reliable data when air temperatures were below -15°C, so all the bad thermal data were replaced with -999. Reliable data from infrared radiometer #3 were obtained only when air temperatures were greater than -15 °C. Infrared thermometer #3 was used to collect trunk temperature at the SSA-OBS and snow surface temperature at the SSA-OA. It is important to note that the wind direction sensor was oriented to true south during installation, except in 1996 when the sensor was oriented to magnetic south. A Brunton compass was used in the orientation of the sensor. This sensor is better oriented to the south because of a 5° "dead zone" between 355° and 360°. Any wind speed data with a value less than 0.0 were changed to 0. 9.3.2 Calculated Variables None. 9.4 Graphs and Plots None. 10. Errors 10.1 Sources of Error Assuming an operative instrument, the primary source of error for the wind direction sensor is in the initial installation and the ability of the installer to accurately orient the monitor. 10.2 Quality Assessment 10.2.1 Data Validation by Source Wind, air temperature, and relative humidity data were compared with Saskatechewan Research Council (SRC) data measured above the canopy. 10.2.2 Confidence Level/Accuracy Judgment Great care was taken to orient the wind monitor during installation. Quantification of the accuracy beyond the manufacturer’s accuracy is difficult. The wind speed data are all below the threshold value of 1.0 m/s; therefore, the data are not absolute. These wind speed data are useful only for determining the occurrence of wind events. Similarly, wind direction data are also useful only during the wind events because wind direction data under calm conditions are meaningless. Temperature and relative humidity data are as good as the accuracy of the instrument. Canopy, trunk, and snow surface temperature data quality are limited by the accuracy of the infrared thermometer. 10.2.3 Measurement Error for Parameters Not available. 10.2.4 Additional Quality Assessments Not available. 10.2.5 Data Verification by Data Center Data that was loaded into the data tables were spot checked against the original ASCII data that was submitted to check for data loading errors. 11. Notes 11.1 Limitations of the Data The wind speed data are all below the threshold value of 1.0 m/s and therefore, the data are not absolute. These wind speed data are useful only for determining the occurrence of wind events. Similarly, wind direction data are also useful only during the wind events because wind direction data under calm conditions are meaningless. 11.2 Known Problems with the Data Infrared thermometer #3 did not provide reliable data when air temperatures were below -15 °C, so all the bad thermal data were replaced with -999. Reliable data from infrared radiometer #3 were obtained only when air temperatures were greater than -15 °C. Infrared thermometer #3 is the third one in the data field. 11.3 Usage Guidance The wind speed data are all below the threshold value of 1.0 m/s; therefore, the data are not absolute. These wind speed data are useful only for determining the occurrence of wind events. Similarly, wind direction data are also useful only during the wind events because wind direction data under calm conditions are meaningless. It is important to note that the wind direction sensor was oriented to true south during installation, except in 1996 when the sensor was oriented to magnetic south. A Brunton compass was used in the orientation of the sensor. This sensor is better oriented to the south because of a 5° "dead zone" between 355° and 360°. 11.4 Other Relevant Information Not available. 12. Application of the Data Set This data set can provide information on the timing and relative magnitude of wind events in the forest and an approximate direction of wind. The data set, in conjunction with data from the tower, also provides insight into the relationship between above-canopy and below-canopy meteorology. 13. Future Modifications and Plans None. 14. Software 14.1 Software Description An undetermined spreadsheet program was used to organize the data. 14.2 Software Access None given. 15. Data Access (This section for BORIS and ORNL DAAC Use) 15.1 Contact Information Ms. Beth Nelson BOREAS Data Manager NASA GSFC Greenbelt, MD (301) 286-4005 (301) 286-0239 (fax) beth@ltpmail.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-03 subcanopy meteorological data are available from the EOSDIS ORNL DAAC (Earth Observing System Data and Information System) (Oak Ridge National Laboratory) (Distributed Active Archive Center). 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 The data are available in tabular ASCII files. 17. References 17.1 Platform/Sensor/Instrument/Data Processing Documentation wind sensor: manual available from manufacturer: R.M. Young Company 2801 Aero-Park Drive Traverse City, MI 49684 (616) 946-3980 datalogger and temp/RH probe: manual available from manufacturer/distributor: Campbell Scientific, Inc. 815 W. 1800 N. Logan, UT 84321-1784 (801) 753-2342 Infrared thermometer manual available from manufacturer: Everest Interscience, Inc. 1120 S. Raymond Fullerton, CA 92631 (800) 422-4342 17.2 Journal Articles and Study Reports Davis, R.E., C. Woodcock, and J.P. Hardy. 1996. Toward spatially distributed modeling of snow in the boreal forest. Eos Transactions, AGU 1995 Fall Meeting, Abstract, p. 218. Davis, R.E., J.P. Hardy, W. Ni, C. Woodcock, C.J. McKenzie, R. Jordan, and X. Li. 1997. Variation of snow ablation in the boreal forest: A sensitivity study on the effects of conifer canopy. Journal of Geophysical Research. 102(D24):29389-29396. Hardy, J.P., R.E. Davis, and J.C. McKenzie. 1995. Snow Distribution Around Trees: Incorporation of snow interception patterns into spatially distributed snow models. Eos Transactions, AGU 1995 Fall Meeting, Abstract, p. 202. Hardy, J.P., R.E. Davis, R. Jordan, X. Li, C. Woodcock, W. Ni, and J.C. McKenzie. 1997. Snow ablation modeling at the stand scale in a boreal jack pine forest. Journal of Geophysical Research. 102(D24): 29397-29406. Ni, W., X. Li, C.E. Woodstock, J.L. Roujean, and R.E. Davis. 1997. Transmission of solar radiation in boreal conifer forests: Measurements and models. Journal of Geophysical Research. 102(D24):29555-29566. 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.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, F.E. Guertin. 1997. BOREAS in 1997: Experiment overview, scientific results, and future directions. Journal of Geophysical Research. 102(D24):28731-28770. 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. 17.3 Archive/DBMS Usage Documentation 18. Glossary of Terms None. 19. List of Acronyms BOREAS - BOReal Ecosystem-Atmosphere Study BORIS - BOREAS Information System CGR - Certified by Group CPI - Certified by Principal Investigator CPI-??? - CPI but questionable CRREL - Cold Regions Research and Engineering Laboratory DAAC - Distributed Active Archive Center EOS - Earth Observing System EOSDIS - EOS Data and Information System FFC-W - BOREAS Focused Field Campaign - Winter FOV - Field of View GMT - Greenwich Mean Time GSFC - Goddard Space Flight Center HYD - Hydrology IR - infrared NASA - National Aeronautics and Space Administration NAD83 - North American Datum of 1983 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 PIR - Precision Infrared Radiometer PRE - Preliminary RH - relative humidity SRC - Saskatchewan Research Council SSA - Southern Study Area temp - Temperature URL - Uniform Resource Locator 20. Document Information 20.1 Document Revision Dates Written: 24-Mar-1997 Revised: 19-Mar-1998 20.2 Document Review Dates BORIS Review: 12-Jan-1998 Science Review: 15-Jul-1997 20.3 Document ID 20.4 Citation The BOREAS HYD-03 subcanopy meteorological data were collected and processed by Janet P. Hardy and Robert E. Davis of US Army CRREL. Their efforts in making these data available are greatly appreciated. 20.5 Document Curator 20.6 Document URL TEMPERATURE WIND SPEED CANOPY TEMPERATURE RELATIVE HUMIDITY HYD03_Subcan_Met.doc Page 15 of 16 04/17/98