Ameriflux Measurements at Fermi National Accelerator Laboratory This file (readme.fer) describes the Ameriflux measurements made by Argonne National Laboratory at two sites within Fermi National Accelerator Laboratory at Batavia, Illinois. SITE DESCRIPTION: Two eddy correlation systems are installed at Fermi National Accelerator Laboratory: one on a restored prairie (established in October 2004) and one on a corn/soybean rotation agricultural field (established in August 2005). The Prairie site had been farmed for more than 100 years, but was was converted to prairie in 1989. The Agricultural site has been farmed for more than 100 years. Both sites have silty clay loam topsoil with clay subsoil. For more information about the sites and the carbon sequestration studies being performed there, see www.atmos.anl.gov/FERMI/. The most frequent wind direction at the two sites is southwest. More than sufficient fetch (400 meters or more) is available for the eddy correlation measurements in all directions at the Agricultural site and in all directions except east (fetch to east is marginal) at the Prairie site. A narrow strip of agricultural land is located about 250 meters due east of the prairie site. The Prairie eddy correlation and meteorological systems are located on the northern portion of a slight rise (2 meters) in the middle of the prairie field and is powered with AC service. The Agricultural eddy correlation and meteorological systems are in the middle of a flat agricultural field, which drops away 1 meter (towards the northern edge) in the northern third of the field and is powered with a 44 V DC solar panel array (voltage dropped to 12 V for the instrumentation). LOCATIONS: Prairie: Latitude 41 deg 50 min 26.22 seconds North, Longitude 88 deg 14 min 27.72 West Agricultural: Latitude 41 deg 51 min 33.48 seconds North, Longitude 88 deg 13 min 21.84 West INSTRUMENTATION: Instrumentation includes the following, listed by measurement (note some minor differences between the two sites): Eddy Correlation: 3-dimensional fast response wind measurements, wind speed, wind direction: Gill R3 Research Ultrasonic Anemometer (Prairie) Gill WindMaster Pro Ultrasonic Anemometer (Agricultural) Fast response air temperature: Gill R3 Research Ultrasonic Anemometer (Prairie) Gill WindMaster Pro Ultrasonic Anemometer (Agricultural) Water Vapor: LI-COR LI-7500 CO2/H2O Analyzer Carbon Dioxide: LI-COR LI-7500 CO2/H2O Analyzer Meteorology: Wind Speed: Gill R3 Research Ultrasonic Anemometer (Primary, Prairie) Gill WindMaster Pro Ultrasonic Anemometer (Primary, Agricultural) Met One 010C (secondary) Wind Direction: Gill R3 Research Ultrasonic Anemometer (Primary, Prairie) Gill WindMaster Pro Ultrasonic Anemometer (Primary, Agricultural) Met One 020C (secondary) Air Temperature: Vaisala HMP45D T/RH probe (Prairie) Vaisala HMP45A T/RH Probe (Agricultural) Relative Humidity: Vaisala HMP45D T/RH probe (Prairie) vaisala HMP45A T/RH Probe (Agricultural) Aspirated Radiation Shield: R. M. Young 43408-2 Barometric Pressure: Met One 7120 Precipitation: Observator (Belfort) OMC-212 heated rain gage Soil Sensors: Soil Moisture: REBS SMP-1 Soil Moisture Probe (4 used, centered at 2.5, 10, 25, and 50 cm) Soil Temperature: REBS STP-1 Soil Temperature Probe (4 used, centered at 2.5, 10, 25, and 50 cm; 2.5 cm probe integrates 0-5 cm) Soil Heat Flow: REBS HFT-3.1 Heat Flow Transducer (3 used, at 5 cm) Radiation: Net Radiation: REBS Q*7.1 Net Radiometer with ventilator PAR: LI-COR LI-190SA Quantum Sensor: 1 each for down-welling and reflected PAR Shortwave: Epply 8-48 pyranometer (Prairie): 1 each for incoming and reflected Albedometer (Agricultural): Scientific Sales Model 3023-A (Schenk Dual Pyranometer 8104) Multispectral Radiometer: Cropscan, Inc. MSR87 Ceptometer (Leaf Area Index): Decagon Devices, Inc. AccuPAR PAR-80 DATA ACQUISITION: Eddy covariance data are acquired at 10 Hz with: Panasonic Toughbook CF-72 laptop running LINUX (Prairie), and: Arcom SBC-GX1 single board computer running LINUX (Agricultural). Meteorological, soil, and radiation measurements are acquired with: Campbell Scientific Inc CR21X datalogger (Prairie), and Campbell Scientific Inc. CR23X Datalogger (Agricultural). All data is presently accessed by a UNIX machine at Argonne National Laboratory, through dedicated cell phones at the sites. The cell phones may eventually be replaced with wireless connections through the Fermi National Accelerator Laboratory infrastructure. The data is stored on a second UNIX machine and later transferred to a third UNIX machine for post-processing. Backups of the data are made to mirrored drives on a LINUX machine. Preliminary, coordinate rotated covariances and variances, as well as meteorological, soil, and radiation data are displayed on the Argonne National Laboratory website mentioned above. DATA FORMAT: Monthly data files of non-gap-filled eddy correlation, meteorological, soil, and radiation measurements are named fermipYYMM.dat (Prairie) and Agricultural) and gap-filled data files are named fermipgapYYMM.dat (Prairie) and fermifgapYYMM.dat (Agricultural) where YY is year and MM is month. These files are submitted monthly to the Ameriflux database at ORNL. The beginning time of the half hour is used for the data timestamp, as is standard for Ameriflux. Outliers are removed from the non-gap-filled data files via post-processing, as well as manually afterwards, before the gap-filling program is run on the data. The data are listed in a single record per half hour, with a 5 line header preceding the data. Note: all data was resubmitted in November 2007 using the new Ameriflux variable names and header. Data fields in the data record are, by variable name and in order (with acceptable ranges): YEAR Year DOY Julian Day HRMIN Hour-Minute (GMT) DTIME Decimal Julian day and time (GMT) FC CO2 Flux (-30 to 30 umol/m2/s) H Sensible Heat Flux (-200 to 1000 W/m2) LE Latent Heat Flux (-200 to 1000 W/m2) UWcvar Kinematic Momentum (-2.25 to -0.0009 cm2/s2) Ta Air Temperature (-30 to 45 deg. C) Rh Relative Humidity (0 to 100 %) Rn Net radiation (-150 to 1000 W/m2) Rg Incoming Shortwave Radiation (0 to 1200 W/m2) Rr Reflected Short Wave Radiation (0 to 600 W/m2) CAlb Canopy Albedo (0 to 0.9) PAR_down Incoming Photosynthetic Active Radiation (0 to 2200 umol/m2/s) PAR_up Reflected Photosynthetic Active Radiation (0 to 2200 umol/m2/s) APAR PAR absorbed by vegetation (0 to 200 umol/m2/s) FPAR Percent of PAR absorbed by vegetation (0 to 15%) WS Wind Speed (0 to 50 m/s) WD Wind Direction (0 to 360) UST Friction Velocity (0.03 to 1.5 m/s) ZL Stability Parameter z/L (-300 to 50) PRESS Barometric Pressure (85 to 110 kPa) PREC Precipitation (0 to 125 mm) FG Surface Soil Heat Flux (-200 to 100 W/m2) TS_2_5 2.5 cm Soil Temperature (-30 to 50 deg. C) TS_10 10 cm Soil Temperature (-30 to 50 deg. C) TS_25 25 cm Soil Temperature (-30 to 50 deg. C) TS_50 50 cm Soil Temperature (-30 to 50 deg. C) SWC_2_5 2.5 cm Soil Water Content (~5 to ~60 % by volume) SWC_10 10 cm Soil Water Content (~5 to ~60 % by volume) SWC_25 25 cm Soil Water Content (~5 to ~60 % by volume) SWC_50 50 cm Soil Water Content (~5 to ~60 % by volume) Flag Non-gap-filled: Indicators of missing data: 00 - data available from both eddy covariance and meteorological systems 10 - data not available from eddy covariance system 01 - data not available from meteorological system 11 - data not available from eddy covariance and meteorological systems Gap-filled: Indicator of gap-filled data if = 1; for each variable. METHODOLOGY: Fluxes of momentum, heat, water vapor, and carbon dioxide are estimated with the eddy covariance method, and supporting and ancillary meteorological, radiation, and soils measurements are taken from a co-located Automatic Weather Station (AWS). The eddy covariance instrumentation is supported on a rigid aluminum tripod tower which is guyed to reduce sway. The meteorological and radiation instrumentation is supported on a 12 inch triangular tower at the Prairie site and on a rigid aluminum tripod tower at the Agricultural site; both are guyed to maintain horizontal level for the wind direction sensor and the radiation instruments. The height of the eddy covariance measurements (mid-point of sonic anemometer volume) is 3.76 m at the Prairie site and 4.05 m at the Agricultural site. The radiation measurements are made at 2.3 m (Prairie) and 2.4 m (Agricultural), T/RH and wind measurements are made at the same height as the sonic anemometers (to allow comparison of temperature and vapor density with the eddy covariance instrumentation), barometric pressure is measured at 1.5 m, and precipitation is measured at 2 m. Most radiation and meteorological measurements are made at a frequency of 1 Hz, whereas some temperature and soil measurements are made every minute. All AWS measurements are averaged to half hour values. Soil water content is measured as % gravimetric and is converted to % by volume in post-processing. Corrections for soil moisture and bulk density are applied to soil heat storage and thus soil heat flux in post processing. Soil water content is restricted to upper and lower bounds in the Campbell datalogger programming; the bounds are determined by the calibration curves of individual sensors. Therefore, only approximate bounds can be stated; 7% for the lower bound and 60% for the upper bound. Soil water contents below or above the range specified above are possible but can not be reliably determined by the instrumentation. Frozen soil conditions also cause inconsistencies in soil water content measurements; soil water content measurements are suspect when the soil temperature is below freezing. The eddy covariance measurements are made at a 10 Hz frequency and block-averaged to half hour values. Sensor delays (CO2/H2O) are compensated for and water vapor refractive index (speed of sound) adjustment for sensible heat flux is applied in the data acquisition process. Adjustments to the fluxes in post processing include: 2 dimensional coordinate rotations, "WPL" adjustments for Stefan flow and "density" (expansion-compression) effects for CO2 and latent heat fluxes, separation and time constant adjustments to the fluxes (following Massman, 2000 analytical approach), removal of negative LE when Rn is positive, removal of LE and CO2 flux when precipitation/dew/frost occurs, and quality control checks for outliers. Water vapor broadening effects on CO2 are compensated for in the LI-7500 CO2/H2O sensor electronics. Outlier data is replaced with 9999 values in post-processing to produce the non-gap-filled data files (including some manual outlier removal). Linear interpolation (for two consecutive half hours at maximum) and gapfilling (using monthly averages of "good" data for each half hour) are performed by a gap filling program to produce the gap-filled data files. CONTACTS: Roser Matamala phone: (630) 252-9270 email: matamala@anl.gov David Cook phone: (630) 252-5840 email: drcook@anl.gov Argonne National Laboratory Building 203 9700 South Cass Avenue Argonne, IL 60439-4803