BOREAS HYD-06 Aircraft Gamma Ray Soil Moisture Data Summary: This data set contains percent soil moisture (by weight) (and/or water content if there is a moss/humus layer) measured from aircraft using a terrestrial gamma ray instrument. There is also data that indicates the location of the aircraft at the time it collected the terrestrial gamma ray data for the various flight lines and bins. The location information contains a list of coordinates that indicate the path of the aircraft for each bin. The data were collected during four time periods from September 1993 to September 1994 over the Southern Study Area (SSA) and two time periods from February to August 1994 over the Northern Study Area (NSA). 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-06 Aircraft Gamma Ray Soil Moisture Data 1.2 Data Set Introduction This data set contains airborne gamma radiation measurements of total available moisture. The total available moisture is the soil moisture (SM) of the mineral soil if there is not a moss/humus layer or standing water. With a moss/humus layer and/or standing water the total available moisture includes the moisture in these two variables (converted from centimeters to percent of soil moisture). 1.3 Objective/Purpose The objectives of this research were: 1) to obtain improved estimates of the soil moisture (SM) conditions for the BOREAS experimental areas, 2) to develop techniques for measuring the water content (WC) of the Moss/Humus layer, 3) to provide assistance to HYD-04 to measure the water equivalent (WE) of the snow cover, 4) to provide information for validating and calibrating other remote sensing methods for measuring soil moisture, and 5) to provide information on SM of the mineral soil, WC of the moss/humus layer, and (in conjunction with HYD-04) the WE of the snow cover to other investigators. 1.4 Summary of Parameters The primary parameter is the airborne gamma radiation measurement of total available moisture. If there is not a moss/humus layer or standing water the airborne estimate is the soil moisture (SM) of the mineral soil. With a moss/humus layer and/or standing water, the total available moisture includes the moisture in these two variables (converted from centimeters to percent of soil moisture). This data set also provides flight line identifiers, latitudes and longitudes of the BOREAS airborne gamma radiation flight lines and for sections (bins) of the flight lines. The bins are equal divisions of the flight lines and the number of bins is controlled primarily by the number of in-situ measurements obtained for calibration of the flight lines. 1.5 Discussion As part of the BOREAS experiment, natural terrestrial gamma radiation data over a network of 48 flight lines were collected. For each flight line, in-situ measurements of the SM of the mineral soil and the WC of the moss/humus were collected and used, along with other available soil moisture measurements, to establish one-time calibration of the natural terrestrial radioisotope signal for the flight lines. 1.6 Related Data Sets BOREAS HYD-06 Moss/Humus Moisture Data BOREAS HYD-06 Ground Gravimetric Soil Moisture Data 2. Investigator(s) 2.1 Investigator(s) Name and Title Dr. Eugene L. Peck Hydex Corporation Dr. Thomas Carroll National Weather Service 2.2 Title of Investigation Remote Sensing of Hydrologic Variables in Boreal Areas 2.3 Contact Information Contact 1: ------------------- Dr. Eugene L. Peck Hydex Corporation Vienna, VA (703) 281-6284 (703) 281-7014 genepeck@aol.com Contact 2: -------------------- Dr. Thomas Carroll NOHRSC, Office of Hydrology NWS, NOAA Chanhassen, MN (612) 361-6610, ext. 225 (612) 361-6634 tc@nohrsc.nws.gov 3. Theory of Measurements Airborne Soil Moisture Measurements Airborne soil moisture measurements are based on the difference between natural terrestrial gamma radiation flux measured for comparatively wet and dry soils. The presence of additional moisture in the soil, and in the moss/humus layer when it exists, increases the mass that radiation emitting from the ground has to go through to reach the radiation sensors in the aircraft. This results in increased attenuation of the gamma flux for relatively wet soil and a correspondingly decrease in the attenuation of the radiation flux for dryer soil conditions. The gamma flux from the ground is a function primarily of the water mass and radioisotopes concentration near the surface of the soil (which remains constant over time). Only the mass of the moisture, not the phase, affects the attenuation of the gamma radiation. The gamma flux originates from the potassium, uranium and thorium radioisotopes in the soil. In a typical soil, 91 percent of the gamma radiation is emitted from the top 10 cm of the soil, 96 percent from the top 20 cm and 99 percent from the top 30 cm. Other sources of radiation, which contribute to gamma flux measurement in the aircraft, include the daughter products of radon gas in the atmosphere, high energy cosmic particles (i.e., greater than 3.0 MeV), and trace sources of radioactivity within the aircraft and the detection system itself (Carroll 1981). Non-differentially corrected GPS (Global Positioning System) was used to locate the aircraft for many of the flight lines. See section 7.3.1 for more information. 4. Equipment: 4.1 Sensor/Instrument Description The airborne detector package consists of five downward-looking 10.2 x 10.2 x 40.6-cm NaI (Tl) scintillation detectors; two 10.2 x 10.2 x 20.3-cm, upward- looking detectors (used to isolate the effects of the random gas contribution); a pulse height analyzer (PHA); a Hewlett-Packard 9825 mini-computer used to reduce and record the output data onto magnetic tape; temperature, pressure, and radar altitude sensors; and a remote control unit used by the system operator or navigator to control and monitor the data collection (Carroll and Allen, 1988). A video camera is used to obtain recording of the area immediately under the aircraft. Video tapes are available for lines flown in September 1993 and during IFC-2 and IFC-3 in 1994. Overview pictures at different altitudes were obtained for the area near the Old Black Spruce, Old Jack Pine, Young Aspen, and flight line BP114 during IFC-3 in the SSA. 4.1.1 Collection Environment During data acquisitions, the nominal altitude for the Aero Commander aircraft is 150 m Above Ground Level (AGL). 4.1.2 Source/Platform The sensing platform is a twin-engine Aero Commander Aircraft. 4.1.3 Source/Platform Mission Objectives To collect spectral gamma radiation information along established flight lines to provide estimates of the mean areal soil moisture, the WC of the Moss/Humus layer, and the WE of the snow cover (in support of HYD-04). 4.1.4 Key Variables The key variable is the airborne gamma radiation measurement of total available moisture. This is the soil moisture (SM) of the mineral soil if there is not a moss/humus layer or standing water. With a moss/humus layer and/or standing water the total available moisture includes the moisture in these two variables (converted from centimeters to percent of soil moisture). 4.1.5 Principles of Operation The 48 flight lines surveyed for the BOREAS investigation averaged 10.7 km in length. Data collected during calibration surveys, in which background gamma radiation data and ground-based soil moisture data are collected simultaneously, are used to calibrate each flight line. Once a flight line is calibrated, airborne soil moisture measurements can be made with no future ground-based data support required. Reliable, real-time, mean areal soil moisture measurements can be made for the upper 20 cm of soil (and of the WC of the Moss/Humus layer) along the flight line once both the background and current, uncollided terrestrial gamma count rates and background soil moisture data are available. To separate the change in the reduction of the radiation due to the moisture in the SM and the WC of the Moss/Humus layer an estimate of the average of one or the other is required. Detailed information on the operation of the airborne gamma radiation system may be found in the users guide (Carroll and Allen 1988). 4.1.6 Sensor/Instrument Measurement Geometry The aircraft flies at an altitude of 150 m AGL and measures natural terrestrial gamma radiation over a path 305 m wide. Consequently, radiation data collected over each BOREAS flight line are mean areal measurements over approximately 3.3 km2. 4.1.7 Manufacturer of Sensor/Instrument The radiation sensors on board the aircraft have been customized by the National Weather Service NOAA, Minneapolis, Minnesota. The manufacturer of the GPS unit used to locate the flight lines is unknown. 4.2 Calibration 4.2.1 Specifications Calibration of the airborne gamma radiation equipment is accomplished by collecting radiation data at different altitudes and using the changing airmass as an attenuation medium. A reliable calibration can be generated in one area and used in another with a different radioisotope concentration. During the calibration procedure, stripping equations are derived for isolating other extraneous sources of radiation (Carroll, 1987). 4.2.1.1 Tolerance The radioisotope concentration in the soil does not significantly change with time; consequently, there is no need for additional background data collection once a radiation spectrum has been collected for a particular flight line. 4.2.2 Frequency of Calibration The airborne technique requires a one-time flight line calibration in which background gamma radiation data and ground-based soil moisture data are collected simultaneously and used to calibrate each flight line. 4.2.3 Other Calibration Information None given. 5. Data Acquisition Methods Airborne Radiation Flight Lines Radiation information was collected for 48 flight lines during the BOREAS field experiment (four of the flight lines were established after the first flights in September 1993). Maps showing locations of all of the 48 established flight lines (except for BP121 over the Old Jack Pine tower site in the SSA, BP122 a north-south line east of the north-south highway to the east of Young Jack Pine and the FEN tower sites in the SSA, and BP123 established over the Young Aspen tower site in the SSA) are shown on Figures 5.2.1.4a, 5.2.1.4b 5.2.1.4c, and 5.2.1.4c of version 3.0 of the BOREAS Experimental Plan. Revised computerized maps of all of the 48 flight lines prepared by NOHRSC have been submitted to BORIS. Location of flight lines Maps showing locations of most of the established flight lines are presented on Figures 5.2.1.4a, 5.2.1.4b, and 5.2.1.4c of version 3.0 of the BOREAS Experimental Plan. Added later were flight lines BP121, BP122, and BP123. The flight lines are numbered BP100 to BP123 and CR954 to CR960 in the southern research area (SSA) and BP201 to BP213 in the northern study area (NSA). Flight lines BP301 to BP305 are located along the transect between the SSA and NSA. The CR lines in the SSA are part of the operational snow measurement program of the Atmospheric Environment Service, AES, of Canada. 6. Observations 6.1 Data Notes None. 6.2 Field Notes Computer tapes of the airborne gamma radiation data for all airborne flights are available (from NOHRSC) but are not in BORIS. A large number of complex computer programs are required for processing the data to obtain the airborne soil moisture estimates. Ground measurements were collected during September 1993 for a proposed north- south flight line on the western side of the highway directly east of the Young Jack Pine and Fen towers sites in the SSA. Ground and airborne observations clearly indicated that the vegetation over the area to be measured by the airborne gamma surveys was highly variable, so much so that any reasonable number of measurements could not provide acceptable information on average conditions along the flight line. Information collected for this proposed line are listed under flight line BP140 in the ground measurements of soil moisture. Very High Cosmic Radiation Observed During the three-day period 8-10 September 1994 very unusual high cosmic radiation was observed during the soil moisture airborne surveys in the SSA. A paper was presented at the BOREAS workshop in Ellicott City, MD on 29-31 March (Peck and Carroll, 1995) describing the collection and analyses of the observed data. The high solar protons that apparently originated from solar flares had not been observed during the entire year of airborne BOREAS surveys. A review of 15 years of approximately 14,000 records for 7 provinces of Canada and 25 states in the United States maintained by NOHRSC of NWS found no case with cosmic radiation as high as that observed during each of the three-day period. Fortunately, procedures developed during the First ISLSCP (International Satellite Land Surface Climatology Project) Field Experiment (FIFE) permit the computation of soil moisture (total moisture) estimates using only radiation collected by the airborne system that are not affected by the high radiation. All BOREAS airborne gamma estimates have been derived using the FIFE procedure. The primary question raised in the paper is "Does the high cosmic radiation observed affect measurements by other BOREAS scientists?" 7. Data Description 7.1 Spatial Characteristics The two BOREAS study areas cover over a million square kilometers in the Canadian Provinces of Saskatchewan and Manitoba. Each of the principle study areas (northern, NSA and southern, SSA) are approximately 50 by 100 km. The flight line locational information provides latitude and longitude (in decimal form) for each flight line. Each flight line is divided into a specific number (varying from 2 to 6) of equally spaced bins (sections). The latitude and longitude of the start and end point of each leg of each bin are provided. The first leg of the first bin begins at the start of the flight line and the final leg of the final bin extends to the end of the flight line. The latitude and longitude given in this data were read automatically by the GPS aboard the aircraft during aerial surveys in February 1995 for all but the following flight lines, BP123, BP301, BP302, BP303, BP304, and BP305. Locations values for BP123 were read off of USGS maps in NAD83. Values for the BP300s lines were read off USGS maps in NAD27 and converted to NAD83 values. All longitude and latitude values in the database are equivalent to NAD83. For each of the four categories of flight lines (BPxxx lines in the SSA, BPxxx lines in the NSA, BPxxx lines along the transect, and the CRxxx lines in the SSA) the number of flight lines and the number of bins are shown in the table in section 7.1.3 (with the average length and the average areal coverage). 7.1.1 Spatial Coverage These data were collected at the two BOREAS study areas. The two study areas are located within a large area of interest covering over a million square kilometers in the Canadian Provinces of Saskatchewan and Manitoba. Each of the study areas is approximately 50 by 100 km. The aircraft flies at an altitude of 150 m AGL and measures natural terrestrial gamma radiation, on average, over an average path 10.7 km long and 305 m wide, or an areal extent of 3.3 km2. Soil moisture and water content of the Moss/Humus layer samples were collected at various points along the flight. The number and timing of the flight lines flown each day were determined by the need for ground calibration and on the basis of need for other studies (priority was given where possible to obtaining measurements over flight lines associated with ground tower sites) and the amount of flight hours remaining for the aircraft before required maintenance. These measurements were made within the NSA and SSA and along a transect that is between these two study areas. There is a reference table called HYD06_TRANSECT_REF that contains information about the location of the various flight lines. NSA Spatial Coverage (North American Datum 1983 (NAD83)) Longitude Latitude --------- ------- Upper Left -98.82 56.247 Upper Right -97.24 56.081 Lower Right -97.49 55.377 Lower Left -99.05 55.54 SSA Spatial Coverage Longitude Latitude --------- -------- Upper Left -106.23 54.319 Upper Right -104.24 54.223 Lower Right -104.37 53.419 Lower Left -106.32 53.513 7.1.2 Spatial Coverage Map The following maps are provided courtesy of the HYD-4 BOREAS team, led by Dr. Barry Goodison. 7.1.3 Spatial Resolution Table 1 Number and average coverage of flight lines and bins of flight lines ----------------------------------------------------------------------------- Category Number of Average Average Number of Average Average Flight Lines Length Area Bins Length Areal km km2 km km2 BP100- 24 8.0 2.4 80 2.4 0.7 BP123 BP201- 13 10.3 3.1 33 4.0 1.2 BP213 BP301- 5 17.0 5.2 15 5.7 1.7 BP305 CR954 7 16.1 4.9 24 4.7 1.4. 7.1.4 Projection The geographic coordinates are NAD83 latitude and longitude values. 7.1.5 Grid Description Not applicable. 7.2 Temporal Characteristics 7.2.1 Temporal Coverage The data was collected for as many flight lines as possible during the following periods: 8-Sep-1993 to 11-Sep-1993 in the SSA 7-Feb-1994 to 11-Feb-1994 in the SSA and NSA (in cooperation with HYD-4) 24-Jul-1994 to 5-Aug-1994 in the SSA and NSA 30-Aug-1994 to 10-Sep-1994 in the SSA 7.2.2 Temporal Coverage Map See 7.2.1 7.2.3 Temporal Resolution Airborne surveys were conducted on a daily basis. The timing of the aerial surveys was controlled by BOREAS operations. 7.3 Data Characteristics Data characteristics are defined in the companion data definition file (h6acgsmd.def). 7.4 Sample Data Record Sample data format shown in the companion data definition file (h6acgsmd.def). 8. Data Organization 8.1 Data Granularity All of the Aircraft Soil Moisture Data are contained in one dataset. Aircraft Transect Reference data are contained in a companion file. 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 (h6acgsmd.def). 9. Data Manipulations 9.1 Formulae 9.1.1 Derivation Techniques and Algorithms 9.2 Data Processing Sequence The airborne radiation data are processed by NOHRSC to compute the calibration radiation window data used for computing the estimates of total moisture for days without observed ground data. The calibration ground data were prepared in table format with average values for flight lines (and each bin of flight lines) of the observed SM of the mineral soil and the WC of the moss/humus layer. 9.2.1 Processing Steps The airborne radiation data are recorded on the aircraft computer for each 5 seconds of flight time. The airborne radiation data are processed by NOHRSC to compute the radiation window values for each flight line and bin. Average flight line and bins values of in-situ measurements of the SM of the mineral soil and the WC of the moss/humus layer are used with the airborne radiation data in calibrating each flight line. The radiation window counts per minute are used with the calibration data for computing the airborne estimates of total moisture. BORIS processed the data by: 1) Reviewing the initial data files and loading them on-line for BOREAS team access, 2) Designing relational data base tables to inventory and store the data 3) Loading the data into the relational data base tables, 4) Performing the following conversions on measurements into System International (SI) units. 4) Working with the HYD-06 team to document the data set, and 5) Extracting the standardized data into logical files. 9.2.2 Processing Changes None. 9.3 Calculations Soil moisture is computed using the current uncollided terrestrial gamma count rate for each of the photopeak windows used by the following equation. soil moisture = ((C0/C)(100 + 1.11 * M0) - 100)/(1.11) where: C = current uncollided terrestrial gamma count for each of the three photopeak windows used, and C0 = Background uncollided terrestrial gamma count rate in each of the three photopeak windows used, and M and M0 = current (airborne) and background (ground-based) soil moisture for the upper 20 centimeters. Soil moisture is defined as soil moisture weight divided by dry sample weight. Incorporated in the above equation are two coefficients: 1.11 represents the ratio of gamma radiation attenuation in water to air; and 100 is used because the percent soil moisture (by weight) is reported as a percentage. The estimated soil moisture for the BOREAS airborne gamma radiation surveys are determined by weighing the estimates computed using the Potassium 40K and Thallium 208Tl windows with the First ISLSCP Field Experiment (FIFE) weighing factors (see Table 2, section 9.3.1) by following equation: soil moisture = 0.565 * (Potassium 40K estimate + 0.435) * Thallium 208Tl estimate 9.3.1 Special Corrections/Adjustments The standard NWS operational procedure uses weighing factors for the potassium (40K, 1.26 - 1.56 mev), thallium (208Tl, 2.41 - 2.81 mev) and Gross Count (0.41 - 3.0 mev) windows to compute estimates computed for each window to a single weighted estimate of the total moisture. Under normal cosmic radiation activity the computed estimates are not significantly different from estimates computed using weighing factors developed during FIFE (Carroll et. al, 1988). The FIFE procedure only uses the potassium and thallium radiation windows values. Since the very high cosmic radiation on 8-10 September 1994 had a very large effect on the Gross Count window measurements and not on the potassium and thallium windows the FIFE weighing factors have been used for all BOREAS airborne estimates. The NWS standard and FIFE weighing factors are shown in Table 2. Table 2 NWS and FIFE radiation windows weighting factors Radiation Window NWS Weighing FIFE Weighing Factors Factors Potassium 40K 0.346 0.565 Thallium 208Tl 0.518 0.435 Gross Count 0.136 0.000 9.3.2 Calculated Variables See other portions of section 9. 9.4 Graphs and Plots Maps of the BOREAS flight lines, digitized by NOHRSC, have been submitted to BORIS. 10. Errors 10.1 Sources of Error There are many possible sources of error in the airborne estimates of soil moisture. Some of these result from abnormally high radon activity, especially if the percent of soil moisture is very low. The largest errors results from non-representative calibration data (Peck et. al, 1992). Fritzsche (1979) discusses the errors associated with the calibration of the gamma radiation system. Errors in the locations of the flight lines and bins are primarily associated with the difficulty in reading the GPS values at the start and end points of the flight lines while flying at 150 meters. Maintaining the aircraft exactly over the flight line during an aerial survey is difficult. Some of the variations in the latitude and longitude values along the flight lines is due to the ability to maintain the aircraft over the flight. 10.2 Quality Assessment 10.2.1 Data Validation by Source Confidence in the airborne gamma radiation estimates of the total moisture depends on many factors regarding the accuracy of the flight line in respect to the flight line flown during calibration of the line. 10.2.2 Confidence Level/Accuracy Judgement The confidence level varies with the experience of the person selecting the flight line or marking the location of the ground measurement for collection of ground calibration data. In very flat areas, the exact location of a ground measurement site is more difficult to identify on a map than a location near a stream or in areas of variable terrain. SM moisture measurements over non- forested areas during the FIFE experiments had a root mean square error of approximately 2.5 percent (Peck, et. al, 1990). 10.2.3 Measurement Error for Parameters The start and end points of flight lines are generally associated with visual ground locations that can be readily located by the aircraft flight crew (roads, trails, streams, or edges of clearings). No error can be determined for locating ground measurement sites from the flight line selected for airborne measurement. The calibration of the flight line is very important in the accuracy of the airborne estimates. The principle objective of calibration is to obtain measurements along the flight line that are representative of the average conditions of the area measured by the system. The selection of the sites for in-situ measurements of the soil moisture and the water content of the moss/humus layer is very critical to the usefulness of measured values. During the development of the airborne system in the United States it was clear that using a grid method to collect soil moisture samples over farm land in Minnesota was not viable. One or more measurements taken in shallow, low ravines, subject to high soil moisture following periods of runoff producing precipitation would result in average soil moisture values for sections of farm land that would not correlate with the airborne estimates. In Minnesota soil moisture observations of average land slope (i.e., one to two percent) of corn fields or other crops were found to be best correlated with airborne measurements (Peck et. al, 1975). 10.2.4 Additional Quality Assessments Experience with the airborne gamma radiation system during FIFE illustrated the need to obtain ground measurements representative of the average of the area from which ground based gamma are received by the airborne detectors. During FIFE a few lines were established in areas where permission to traverse the entire line on foot was not possible. Airborne estimates for other days without ground truth measurements showed that the estimated values tended to be reasonable when the average soil moisture of the future flight was approximately equal to that obtained during calibration. However, during periods when the average soil moisture departed significantly, either high or low, from the calibration average, the estimates for one or more bins along the line would appear to be exceptionally high or low (Peck 1992). During the BOREAS field experiments careful attention has been given to obtaining as representative measurements of in-situ soil moisture along the flight lines as possible. Most of the originally established flight lines were located over areas having as consistent vegetative cover as possible (i.e., all Old Aspen). However, in some areas, due to heterogeneous conditions, it was not possible to judge what measurements would provide representative averages. Initially a flight line on west side of the north-south highway just east of the FEN and YJP sites in the SSA was considered. While collecting soil moisture and moss/humus measurements along the proposed line it was clear the large variability in the vegetative cover (from open areas, to burned areas, to heavy forested areas) made it impractical to obtain representative measurements and the attempt to establish a line was given up. The ground data for this proposed line are in BORIS under flight line BP140. Later a request was received for a north- south line east of the same highway. Flight line BP122 was established and flown for most of the l994 field experiment. Review of the estimates obtained for line BP122 indicate the soil moisture estimates are inconsistent with expected conditions and most, if not all of the estimates, have been disregarded. When the flight and bins estimates are consistently in line with other measurements, for all ranges of conditions, it is clear that the calibration of the line is representative. The calibration of most of the flight lines in the SSA appear to be very good and the soil moisture estimates are considered to be very representative. The experience of the person selecting the in-situ sites and the consistency of the vegetative cover over the flight line are the two most important factors for obtaining representative calibrations of flight lines and maintaining quality control. Even with careful attention to selection of the ground measurement sites for calibration, the airborne estimates for a few bins along some flight lines have been found to be non-representative. For these lines the estimated values for soil moisture conditions that varied considerably from those during calibration are either much higher or lower than those for nearby bins or flight lines. During evaluation of the airborne estimate it is generally evident which bins calibration data are not representative. Estimates for bins (or flight lines) that are clearly out of line have been disregarded. When the data are questionable the data have been labeled as non-representative with a CRTFCN_CODE of CPI-??? and -888 as the data value. All of the airborne estimates are being checked by comparison with available soil moisture measurements along the same and nearby lines. As additional soil moisture values become available additional quality control will be accomplished. 10.2.5 Data Verification by Data Center These data were reviewed to make sure that data were loaded properly. 11. Notes 11.1 Limitations of the Data None given. 11.2 Known Problems with the Data See section 10. 11.3 Usage Guidance The airborne gamma radiation soil moisture estimates are only representative for the soil and vegetative conditions of the measured flight line. Considerable change in soil conditions may be found over short distances, even for the same vegetative cover. Careful review of the soil and vegetative conditions are necessary to transfer the soil moisture estimates to nearby areas. However, the use of the airborne estimates for flux analyses and other studies can add considerable information on the spatial and temporal variation in the SM of the mineral soil and of the WC of the moss/humus layer. Maps and digital values of average soil moisture for each one-half square kilometer for the entire FIFE area have been prepared using all available soil moisture information (Peck and Hope, 1995). The report by Peck and Hope indicates the difficulty in preparing such maps but also present cases showing the utility of such information. 11.4 Other Relevant Information None. 12. Application of the Data Set The use of the airborne estimates for flux analyses and other studies can add considerable information on the spatial and temporal variation in the SM of the mineral soil and of the WC of the moss/humus layer. Maps and digital values of average soil moisture for each one-half square kilometer for the entire FIFE area have been prepared using all available soil moisture information (Peck and Hope, 1995). Similar information can be developed from the BOREAS data. The report by Peck and Hope indicates the difficulty in preparing such maps but also present cases showing the utility of such information. 13. Future Modifications and Plans None. 14. Software 14.1 Software Description None given. 14.2 Software Access None given. 15. Data Access 15.1 Contact Information Primary contact: Ms. Beth McCowan BOREAS Information System NASA Goddard Space Flight Center Greenbelt, Maryland (301) 286-4005 (301) 286-0239 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-06 aircraft soil moisture 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 Video tapes taken over each flight line during calibration showing the area directly under the aircraft are available at NOHRSC. At the present time no decision has been made on storing these tapes in BORIS. 16.3 Other Products Maps showing the flight lines for which Gamma data were obtained, have been digitized by NOHRSC and submitted to BORIS. These maps appear as figures 5.2.1.4a, 5.2.1.4b 5.2.1.4c, and 5.2.1.4c in version 3.0 of the BOREAS 1994 Experiment Plan. The data are available as tabular ASCII files. 17. References 17.1 Platform/Sensor/Instrument/Data Processing Documentation Carroll, T. R. 1987. Operational remote sensing of snow water equivalent and soil moisture in the United States using natural terrestrial gamma radiation, J. Int., Asso. Hydro. Sci., IAHS Pub. 166:213-223. Carroll, T. R., and M. Allen, 1988. Airborne gamma radiation snow water measurements and soil moisture measurements and satellite areal extent of snow cover measurements: A user's guide, Version 3.0., Office of Hydrology, National Weather Service, Minneapolis, MN. Fritzsche, A. E. 1979. The development of an airborne gamma radiation system for snow surveys. Remote sensing of snow and soil moisture by nuclear techniques, WMO Workshop, Voss, Norway, April 23-27. 17.2 Journal Articles and Study Reports Carroll, T. R. 1981. Airborne soil moisture measurements using natural terrestrial gamma radiation. Soil Sci. 132:358-366. Carroll, T. R., E. L. Peck, and D. M. Lipinski, 1988. Airborne time-series measurements of soil moisture using terrestrial gamma radiation. Proc. Ann. Conf. Am. Soc. Photogram. Remote Sens., St. Louis, MO. Peck, E. L., 1992. Airborne Gamma Radiation Measurements of Soil Moisture During FIFE, Activities and Results, Hydex Final Report, NASA Contract NAS5- 30959, April. In FIS. Peck, E. L., T. R. Carroll, 1995. High Cosmic Radiation in BOREAS Area, Presented at BOREAS conference, Ellicott City, MD, 29-31 March, 6 pg, 2 charts, In BORIS Peck, E. L., T. R. Carroll, and D. M. Lipinski, 1990. Airborne gamma radiation soil moisture measurements over short flight lines. Symp. on the First ISLSCP Field Experiment, Anaheim, CA, American Meteorological Soc., Boston Massachusetts, p. 79-84. Peck, E. L., T. R. Carroll, and D. M. Lipinski, 1992. Airborne Soil Moisture Measurements for First International Satellite Land Surface Climatology Program Field Experiment, Jour. Geophys. Res. 97, No. D17, p. 18,961-18,967, Nov 30. Peck, E. L., and A. S. Hope, 1995. Spatial Patterns of Soil Moisture for the FIFE Study Area Derived from Remotely Sensed and Ground Data. Submitted for 2nd FIFE Special Issue of American Geophysical Research Journal of Geophysical Research, Available in FIS. Peck, E. L., L. W. Larson, F. K. Farnsworth, and T. L. Dietrich, 1975. Comparison of Aerial Passive Gamma and Passive Microwave Techniques for Measurement of Soil Moisture, Proc. 10th International Symp. On Remote Sensing of the Environment, Environment Res. Institute of Michigan, Ann Arbor, MI, Oct. Sellers, P., F. Hall. 1994. Boreal Ecosystem-Atmosphere Study: Experiment Plan. Version 1994-3.0, NASA BOREAS Report (EXPLAN 94). Sellers, P., F. Hall. 1996. Boreal Ecosystem-Atmosphere Study: Experiment Plan. Version 1996-2.0, NASA BOREAS Report (EXPLAN 96). Sellers, P., F. Hall, K.F. Huemmrich. 1996. Boreal Ecosystem-Atmosphere Study: 1994 Operations. NASA BOREAS Report (OPS DOC 94). Sellers, P., F. Hall, 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., F. Hall. 1997. BOREAS Overview Paper. JGR Special Issue (in press). 17.3 Archive/DBMS Usage Documentation None. 18. Glossary of Terms None. 19. List of Acronyms AES - Atmospheric Environment Service of Canada AGL - Above Ground Level BOREAS - BOReal Ecosystem-Atmosphere Study BORIS - BOREAS Information System BPI - Byte per inch CCT - Computer Compatible Tape CD-ROM - Compact Disk (optical), Read-Only Memory DAAC - Distributed Active Archive Center EOS - Earth Observing System EOSDIS - EOS Data and Information System EXP - Experiment FIFE - First ISLSCP Field Experiment FIS - FIFE Information System (NASA) GMT - Greenwich Mean Time GPS - Ground positioning system GSFC - Goddard Space Flight Center HYD-4 - Group 4, BOREAS Hydrology science team HYD-6 - Group 6, BOREAS Hydrology science team ISLSCP - International Satellite Land Surface Climatology Project Mev - Million Electronic Volts NAD27 - North American datum of 1927 NAD83 - North American datum of 1983 NASA - National Aeronautics and Space Administration NOHRSC - National Operational Hydrologic Remote Sensing Center NSA - Boreas northern study area NWS - National Weather Service OA - Old Aspen OBS - Old Black Spruce OJP - Old Jack Pine ORNL - Oak Ridge National Laboratory SM - Soil moisture, percent by weight, of the mineral soil SSA - Boreas southern study area URL - Uniform Resource Locator USGS - U. S. Geological Survey WC - Water content of the moss/humus layer WE - Water equivalent of the snow layer YJP - Young Jack Pine 20. Document Information 20.1 Document Revision Date Written: 8-Jun-1995 Last Revised: 26-Feb-1998 20.2 Document Review Dates BORIS Review: 17-Nov-1997 Science Review: 19-Dec-1997 20.3 Document ID 20.4 Citation Eugene L. Peck, President, Hydex Corporation Thomas Carroll, Chief, NOHRSC 20.5 Document Curator 20.6 Document URL Keywords SOIL MOISTURE HYD06_AIRSM.doc Page 1 of 17 04/17/98