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EMS - Canopy-Atmosphere Exchange of Carbon, Water and Energy

HF004 EML Publications Archive

Data

Overview

  • Lead: William Munger, Steven Wofsy
  • Investigators: Carol Barford, Shawn Urbanski
  • Contact: J. William Munger
  • Start date: 1990-01-01
  • End date: ongoing
  • Location: Prospect Hill Tract (Harvard Forest)
  • Latitude: +42.537755
  • Longitude: -72.171478
  • Elevation: 340 meters
  • Taxa:
  • Research topic: atmosphere
  • Study type: long-term measurement
  • LTER core area: primary production, inorganic nutrients
  • Keywords: carbon budget, CO2, eddy covariance, evapotranspiration, heat flux, humidity, momentum flux, net ecosystem exchange, temperature
  • Release date: 1999
  • EML version: knb-lter-hfr.4.9
  • Revisions:
  • Related links:
  • Abstract:

    The tower-based CO2 measurements and key meteorological drivers are intended to examine how regional and ecosystem level processes in a mid-latitude forest contribute to global carbon cycling. Specifically, we endeavor to understand quantitatively how and why forested ecosystems take up or release carbon, on time scales from hours to decades, and to elucidate responses to climate changes and management interventions.

    The tower was installed 1989 and the resulting eddy-flux measurements constitute the longest running record of the net-ecosystem carbon exchange in a North American Forest. The resulting long-term record of Net Ecosystem Exchange (NEE) has shown the effects of climate anomalies on carbon fluxes for seasonal and annual time scales. For example, reduced soil frost allows greater respiration in the winter leading to lower C sequestration. Cumulative gross photosynthesis depends on when the canopy emerges in the spring. Warmer springtime temperatures lead to greater uptake of C. As the NEE record is extended and augmented by supporting ecological measurements, we can further identify longer-term effects of climate perturbations on carbon fluxes and further define the relationship between stand history and carbon sequestration. Climatic anomalies in one season or year may have a longer-term effect on the sequestration of carbon in subsequent seasons or years.

    The flux and ecological measurements are coordinated with studies at other sites through the AmeriFlux network. By examining the relationships between carbon fluxes and the driving physical and biological variables across a range of sites we are enhancing understanding of the processes that control NEE.

  • Methods:

    Vertical and horizontal wind speeds and sonic temperature are determined using an ATI Sonic Anemometer mounted at 29m. Wind speed and direction and momentum and sensible heat fluxes are computed from the anemometer data. Fast-response CO2-H2O are determined by closed-path IR-Absorbance analyzer. Vertical fluxes are computed on 30-min intervals. Concentration profiles of CO2 are determined by closed-path IR absorbance analyzer sampling from inlets at 30,24,18,12,6, 3,1,0.05m. Calibrated using a pair of absolute standards that bracket the range of ambient concentration. Air temperatures are measured using 30kW thermistors and relative humidity is measured using thin-film capacitor sensors mounted in aspirated radiation shields at 30,22,12,6,3m. Soil temperatures at the litter-soil interface and 20cm 50cm depth are measured with 30kW thermistors. Photosynthetically active photon flux density is determined by Quantum sensors at 29 and 12m. Net radiation is measured using a net radiation sensor.

  • Use:

    This dataset is released to the public and may be freely downloaded. Please keep the designated Contact person informed of any plans to use the dataset. Consultation or collaboration with the original investigators is strongly encouraged. Publications and data products that make use of the dataset must include proper acknowledgement. For more information on LTER Network data access and use policies, please see: http://www.lternet.edu/data/netpolicy.html.

  • Citation:

    Munger W, Wofsy S. 1999. EMS - Canopy-Atmosphere Exchange of Carbon, Water and Energy. Harvard Forest Data Archive: HF004.

Detailed Metadata

hf004-01: final data

  1. Year: year for data point (YYYY)
  2. Month: month for data point (MM)
  3. seq_from_1990(days): data point time given as sequential day starting at Jan 1, 1990 (EST noon on 1/1/90 = 1.5). Time given at start of hourly intervals. (DDD)
  4. time_days: day of year (DDD.HHHH)
  5. wspd_m/s: wind speed measured by sonic anemometer at 29m (metersPerSecond )
  6. wdir_deg(true): wind direction measured by sonic anemometer at 29m (degree )
  7. eddyT_deg-C: temperature sonic anmemometer speed of sound measuremnet (celsius )
  8. eddyQ_e-3mol/mol: water vapor concentration at 29 m determined by Licor CO2/H2O sensor (millimolesPerMole )
  9. O3mlb_ppb: inferred concentration from fast response ozone detector (partsPerBillion )
  10. NOy_ppt: total nitrogen oxides concentration (partsPerTrillion )
  11. sNOy_ppt: standard deviation of NOy concentration in the hour (partsPerTrillion )
  12. CO_ppb: CO concentration at 29m (partsPerBillion )
  13. sCO_ppb: standard deviaion of CO concentraition in the hour (partsPerBillion )
  14. FCO2_e-6mol/m2/s: observed CO2 eddy covariance fluxes at 29m (micromolesPerMeterSquaredPerSecond )
  15. Fmom_cm2/s2: covariance of vertical and horizontal windspeed (number )
  16. Fheat_W/m2: sensible heat flux at 29 m (wattsPerSquareMeter )
  17. FH2O_e-3mol/m2/s: water vapor eddy covariance flux (millimolesPerMeterSquaredPerSecond )
  18. Fo3_e-6mol/m2/hr: ozone eddy covariance flux (micromolesPerMeterSquaredPerHour )
  19. Fnoy_e-6mol/m2/hr: NOy covariance flux (micromolesPerMeterSquaredPerHour )
  20. RNET_W/m2: net radiation measured by net radiation sensor at 29m (wattsPerSquareMeter )
  21. PAR@12.7m_uE/m2/s: photosynthetically active photon flux at 12.7m, just below main canopy (microEinsteinsPerSquareMeterPerSecond )
  22. PAR@29m_uE/m2/s: photosynthetically active photon flux at 29m, which is above the canopy (microEinsteinsPerSquareMeterPerSecond )
  23. RH@27.9m_%: relative humidity at top level 27.9 m (measured in aspirated shield) (dimensionless )
  24. RH@22.6m_%: relative humidity at second level 22.6 m (dimensionless )
  25. RH@15.4m_%: Relative humidity at third level 15.4 m (dimensionless )
  26. RH@7.6m_%: relative humidity at fourth level 7.6 m (dimensionless )
  27. RH@2.5m_%: relative humidity at ground level 2.5m (dimensionless )
  28. Ta@27.9m_deg-C: ambient air temperatures at 27.9m (measured in aspirated shield by precision thermistor) (celsius )
  29. Ta@22.6m_deg-C: ambient air temperature at 22.6m (celsius )
  30. Ta@15.4m_deg-C: ambient air temperature at 15.4m (celsius )
  31. Ta@7.6m_deg-C: ambient air temperature at 7.6m (celsius )
  32. Ta@2.5m_deg-C: ambient air temperature above ground at 2.5m (celsius )
  33. Ts@srfm_deg-C: mean temperature at the soil surface (litter-soil interface) average of multiple measurement points (celsius )
  34. Ts@50m_deg-C: soil temperature at 50cm (single point) (celsius )
  35. Ts@20m_deg-C: soil temperature at 20cm (celsius )
  36. CO2_ppm: ambient CO2 concentration from continuous fast-response analyzer 29m (partsPerMillion )
  37. CO2stg_e-6mol/m2/s: CO2 storage term d/dt (integrated column concentration 0-29m) (micromolesPerMeterSquaredPerSecond )
  38. Pamb_Pa: ambient atmospheric pressure (pascal )
  39. Ts_srf.adj: adjusted soil surface accounting for changing sensor response beneath accumulating litter. Not computed after 2000 - sensor position adjusted for annual litter accumulation. (celsius )

hf004-02: filled data

  1. Year: year (YYYY)
  2. month: month: 1:12 = January - December (MM)
  3. DoY: day of year; January 1 = 1 (DDD)
  4. Hour_(EST=GMT-5): hour of day in EST; (EST=GMT-5) (hh)
  5. seq_day.90: sequential day starting in 1990, 1 = Jan. 1 1990 (DDD)
  6. seq_time.90: sequential time in fractional days; 1.5 is 12 noon January 1 1990 (DDD)
  7. obs.NEE_e6mol/m2/s: observerd NEE (FCO2 + storage) in micromoles CO2/m2/s (micromolesPerMeterSquaredPerSecond )
  8. obs.FCO2_e-6mol/m2/s: observed FCO2 (CO2 eddy covariance flux) in micromoleCO2/m2/s (micromolesPerMeterSquaredPerSecond )
  9. fco2.corr_e-6mol/m2/s: observed FCO2 + storage correction (micromolesPerMeterSquaredPerSecond )
  10. ustar_cm/s: observed u* (u* = sqrt(-1 * <u'w'>) in cm/s (centimetersPerSecond )
  11. nee_e-6mol/m2/s: net ecosystem exchange filled by model in micromole CO2 /m2/s (micromolesPerMeterSquaredPerSecond )
  12. Resp.e_e-6mol/m2/s: ecosystem respiration filled and derived (see below) e-6mol/m2/s (micromolesPerMeterSquaredPerSecond )
  13. gee_e-6mol/m2/s: gross ecosystem exchange derived and filled (micromolesPerMeterSquaredPerSecond )
  14. C.flag1: 1 when NEE is filled (nee.obs is NA)
    • 1: NEE is filled
  15. C.flag2: 1 when estimated NEE = observed FCO2 + ‘storage adjustment’
    • 1: estimated NEE = observed FCO2 + ‘storage adjustment’
  16. obs_Ta_@27m_C: observed air temperature at 27 m (top of tower) (celsius )
  17. Ta@27m.filled_C: filled air temperature with missing points replaced by available data (celsius )
  18. TA1.flag1: 1when Tair interpolated from adjacent profile heights
    • 1: Tair interpolated from adjacent profile heights
  19. TA1.flag2: 1when Tair filled from sonic temperature
    • 1: Tair filled from sonic temperature
  20. TA1.flag3: 1when Tair filled from Fisher Meterological Station data
    • 1: Tair filled from Fisher Meterological Station data
  21. Ta1.flag4: 1when Tair from daily mean at Shaler Met Station and mean 24-hour cycle
    • 1: Tair from daily mean at Shaler Met Station and mean 24-hour cycle
  22. Ta@2.5m_C: observed air temperature at 2.5m above ground (celsius )
  23. Ta@2.5m.filled_C: filled air temperature at 2.5 m above ground (celsius )
  24. Ta5.flag1: 1when Tair interpolated from adjacent profile heights
    • 1: Tair interpolated from adjacent profile heights
  25. Ta5.flag2: 1when Tair filled from sonic temperature
    • 1: Tair filled from sonic temperature
  26. Ta5.flag3: 1when Tair filled from Fisher Meterological Station data
    • 1: Tair filled from Fisher Meterological Station data
  27. Ta5.flag4: 1when Tair from daily mean at Shaler Met Station and mean 24-hour cycle
    • 1: Tair from daily mean at Shaler Met Station and mean 24-hour cycle
  28. PAR@28m_e-6mol/m2/s: observed photosynthetically active radiation (PPFD) at 28m (above the canopy) (micromolesPerMeterSquaredPerSecond )
  29. PAR@28m.filled_e-6mol/m2/s: filled photosynthetically active radiation (PPFD) (micromolesPerMeterSquaredPerSecond )
  30. P.flag1: 1when missing nighttime points set to 0
    • 1: missing nighttime points set to 0
  31. P.flag2: 1when filled from SUNY-ASRC data
    • 1: filled from SUNY-ASRC data
  32. P.flag3: 1when estimated from global radiation at Fisher Met Station
    • 1: estimated from global radiation at Fisher Met Station
  33. P.flag4: 1when filled with hourly mean in a 30 day window
    • 1: filled with hourly mean in a 30 day window
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