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BOREAS FOLLOW-ON FLX-01 NSA-OBS DERIVED DATA - NEE, GEE, AND RESPIRATION
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Summary

The BOREAS Follow-On FLX-1 team derived NEE, GEE, and Respiration using measured tower CO2 flux measurements taken at the NSA-OBS site. The data provided contain half-hourly measurements as well as 4 and 5 day binned data sets. The derived data covers the period from March 1994 through the end of 1998. The derived data described here are available in tabular ASCII files.
      Flux data from NSA-OBS that were collected after the final BOREAS field season (late 1996 through the end of 1998) are described in the document BOREAS FLX-1 NSA-OBS Tower Flux, Meteorological, and Soil Temperature Data. The FLX-1 (BOREAS legacy TF-3) team efforts at the NSA-OBS site are ongoing. Updates and data beyond 1998 may be available at the group's Web site: http://atmos.seas.harvard.edu/lab/data/boreasdata.html [Internet Link].

Data Citation

Cite this data set as follows (citation revised on October 30, 2002):

Wofsy, S. C., and A. Dunn. 2001. BOREAS Follow-On FLX-01 NSA-OBS Derived Data - NEE, GEE, and Respiration. Data set. Available on-line [http://www.daac.ornl.gov] from Oak Ridge National Laboratory Distributed Active Archive Center, Oak Ridge, Tennessee, U.S.A.

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 Follow-on FLX-01 NSA-OBS Derived Data - NEE, GEE, and Respiration

1.2 Data Set Introduction
      The Boreal-Ecosystem Atmosphere Study (BOREAS) Follow-On Flux Team (FLX)-1, that participated in the BOREAS project as Tower Flux (TF)-3 team, measured tower flux, surface meteorological, and soil temperature at the Northern Study Area (NSA)- Old Back Spruce (OBS) site from 1994 through 1998. The data described here were derived from continuous data collection efforts by this group at the NSA-OBS site. Derived data include Net Ecosystem Exchange (NEE), Gross Ecosystem Exchange (GEE), and Respiration. Data are available from March 1994 through the end of 1998. The measurements at NSA-OBS are ongoing and regular updates are made on the group's web site, where other useful data are also available (http://atmos.seas.harvard.edu/lab/data/boreasdata.html [Internet Link]).

1.3 Objective/Purpose
      The objective of this study was to determine the net ecosystem exchange of CO2 and the surface energy budget.

1.4 Summary of Parameters

Derived data 30-min:
Multi-day binned data: 
GEE, NEE, and respiration
GEE, NEE, and Respiration
      For each multi-day temporal bin:
      mean of all half-hour measurements, mean daily sum, 
      multi-day sum, cumulative sum since 1/1/1994

1.5 Discussion
      NEE is determined from the half-hour averages of CO2 flux from the tower. Respiration is calculated from NEE using a temperature-based regression determined during nights when the atmosphere is well mixed. GEE is then determined by subtracting respiration from NEE, and serves as a proxy for photosynthesis.

1.6 Related Data Sets
BOREAS TF-03 NSA-OBS Tower Flux, Meteorological, and Soil Temperature Data
BOREAS TF-09 NSA OJP Tower Flux, Meteorological, and Soil Temperature Data
BOREAS TF-09 SSA OBS Tower Flux, Meteorological, and Soil Temperature Data
BOREAS TF-10 NSA Fen and YJP Flux, Meteorological, and Soil Temperature Data
BOREAS TGB-01 NSA CH4 and CO2 Chamber Flux Data
BOREAS TE-06 Forest Biophysical Measurements
BOREAS TE-09 NSA Photosynthetic Response Data
BOREAS Follow-on FLX-1 NSA-OBS Tower Flux, Meteorological, Soil Temperature Data

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2. Investigator(s)

2.1 Investigator(s) Name and Title
      Steven C. Wofsy, Abbot Lawrence Rotch Professor of Atmospheric and Environmental Science

2.2 Title of Investigation
      Eddy Correlation Flux Measurements of CO2 and H2O for BOREAS (NSA-OBS).

2.3 Contact Information

Contact 1:
Allison Dunn
Harvard University
Cambridge, MA
(617) 495-4566
(617) 495-2768 (fax)
ald@io.harvard.edu

Contact 2:
Steve Wofsy
Harvard University
Cambridge, MA
(617) 495-4566
(617) 495-9837 (fax)
scw@io.harvard.edu

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3. Theory of Measurements

NEE is determined from the half-hour averages of CO2 flux from the tower measurements. Respiration is calculated from NEE using a temperature-based regression calculated during nights when the atmosphere is well mixed. GEE (Gross Ecosystem Exchange) is then derived by subtracting Respiration from NEE.
      For the derived data, an additional data gap filling routine is performed to improve data quality and coverage. NEE is replaced with the calculated Respiration during non-windy nights, as the atmosphere is not well mixed and the tower measurements are less accurate. This is done on a half-hourly basis, filling in where u* is less than 0.20 m/s. Missing daytime GEE is calculated during the summer based on the amount of photosynthetically active radiation. Missing NEE data during summer days are approximated by adding the interpolated GEE data to the calculated Respiration.
      This process helped to create a more complete suite of half-hourly measurements for the next processing step, which was the calculation of daily and multi-day averages and cumulative sums of NEE, GEE, and respiration. The data are divided into 4 and 5 day periods (longer if there are gaps in the data) and daily averages across this time period are calculated. Combining 4 and 5 days of data helped to mitigate the problem of missing data during rainstorms, etc. This method of data analysis is described in more detail in Goulden et al., 1997, and 1998. Additional discussions can be found in Goulden et al. 1996.

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4. Equipment

4.1 Sensor/Instrument Description
4.1.1 Collection Environment
      Data were collected from the NSA-OBS tower. The sonic anemometer was located at a height of 29 m on a 31 m triangular cross-section radio tower (Rohn 25-G). Air temperature profiles were measured at 27.0 m, 8.2 m, and 1.15 m above ground level. Relative humidity was measured at 27.0 m. Wind speed and direction were measured at 29.6 m. Under-canopy PPFD sensor arrays were placed at ground level.

4.1.2 Source/Platform

Applied Technology Inc. Sonic Anemometer
Sensor height above ground                  29 m
Sampling rate                               4 Hz

LiCor 6262 infrared gas analyzer (IRGA)
Sensor height above ground                  28.5 m
Sampling rate                               4 Hz

Campbell Scientific CR10 Data logger
4.1.3 Source/Platform Mission Objectives
      The tower was erected to support various instruments installed within and above the forest canopy for collecting flux data at NSA-OBS.

4.1.4 Key Variables
      Respiration, NEE, GEE

4.1.5 Principles of Operation

Sonic Anemometer (Applied Technology Inc.):
      Three-dimensional orthogonal wind velocities (u, v, and w) and virtual temperature (Tv) were measured with a sonic anemometer. The path length between transducers was 0.15 m. The sensor software corrected for transducer shadowing effects (see Kaimal et al., 1990). Virtual temperature heat flux was converted to sensible heat flux using algorithms described by Kaimal and Gaynor (1991) and Schotanus et al. (1983).

Infrared Absorption Spectrometer (LiCor 6262 IRGA):
      Water vapor and CO2 concentrations were measured with a closed-path infrared absorption spectrometer.

4.1.6 Sensor/Instrument Measurement Geometry
      The sonic anemometer was located at a height of 29 m on a 31 m triangular cross-section radio tower (Rohn 25-G). The tubing inlet for the air sample was located 0.5 m below the sonic anemometer. The LiCor sensors were placed in a climate-controlled hut 20 m northeast of the tower. The air was drawn down the tower at 18 standard liters per minute. The air was passed through a thermostated block to stabilize the temperature and drawn through the LiCor at 4 standard liters per minute. Pressure was controlled in the cell of the LiCor at 53 kPa.
      Air temperature profiles were measured at 27.0 m, 8.2 m, and 1.15 m above ground level. Relative humidity was measured at 27.0 m. Wind speed and direction were measured at 29.6 m. The sonic anemometer was mounted at 29 m. Under-canopy PPFD sensor arrays were placed at ground level.

4.1.7 Manufacturer of Sensor/Instrument
ATI
Applied Technologies
6395 Gunpark Dr
Boulder, CO 80301-3390

Campbell Scientific Instruments
P.O. Box 551
Logan, UT 84321

LiCor
P.O. Box 4425
Lincoln, NE 68504-0425

MKS Instruments
6 Shattuck Rd
Andover, MA 01810-2495

4.2 Calibration
4.2.1 Specifications
      Sonic anemometer: Supplied by the manufacturer. Instrument zeros and maintenance performed at least twice per year.
      CO2 sensor: Calibrated every 3 hours by standard addition of 4% CO2 at 40 and 80 standard milliliters per minute for 2 minutes 15 m below the sample inlet on tower. Zero datum for the LiCor IRGA was achieved by passing sample air through a column of soda lime for 2 minutes.
      H2O sensor: Calibration was checked by comparison with a Vaisala probe on the tower. Zero information was recorded every 3 hours by passing sample air through a column of magnesium perchlorate for 2 minutes. The calibration information supplied by the manufacturer was used.
      CO2 concentration calibration: Used an independent LiCor 6262 IGA and two span gases (340 ppm and 420 ppm). These gas samples are traceable to the 1993 Scripps-World Meteorological Organization (WMO) standard. Calibrations were done every 3 hours by passing each of the gases through the LiCor IGA at 1.25 standard liters per minute for 2 minutes. Zero information was achieved by the same method as that used for the eddy CO2 sensor.
4.2.1.1 Tolerance
      Not known.


4.2.2 Frequency of Calibration
      Sonic anemometer: Instrument zeros and maintenance performed at least twice per year.
      CO2 sensor: Calibrated every 3 hours by standard addition of 4% CO2 at 40 and 80 standard milliliters per minute for 2 minutes 15 m below the sample inlet on tower.
      H2O sensor/CO2 sensor: The LiCors are replaced, on average, every year with a newly calibrated instrument.
      O2 concentration calibration: Calibrations are done every 3 hours by passing each of the gas samples through the LiCor at 1.25 standard liters per minute for 2 minutes.

4.2.3 Other Calibration Information
      Not known.

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5. Data Acquisition Methods

Data for flux measurements were continuously recorded at 4 Hz while other parameters were recorded at 0.5 Hz. The data were stored on a PC and downloaded once per week. The delay time between the wind speed and concentration measurement was calculated at 5.5 seconds. The time constant for the response time of the instrument to a change in the mixing ratio of the air sample was determined to be 0.6 seconds for CO2 and 1.25 seconds for H2O. The difference in time was due to adsorption of H2O to the tubing. The response-time corrections typically were 5 to 10% during the day and 15 to 25% at night. An averaging time of 30 minutes was used and a linear least-squares regression was used to detrend the flux data.

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6. Observations

6.1 Data Notes
      Data are available from 1994-1998. The measurements are ongoing and regular updates are made on the group's FTP server. The FTP server can be found at ftp://ftp.as.harvard.edu/pub/nigec/Boreas_OBS/ [Internet Link] and data can be directly downloaded.
      A wide range of other useful data are also available on the server such as soil temperature, Photosynthetically Active Radiation, net radiation, momentum flux, etc.
      Note that no GEE and Respiration data exist before 30-Oct-94. The reason for this is because of the way we approached the data initially. Early on the processing and binning procedure were performed on 'ecological years', i.e., from the end of October-end of October the following year. Insofar as GEE and Respiration are more 'derived' quantities than NEE, they were summed according to this timeframe and have remained that way. As NEE is the quantity we usually use to determine the annual course of carbon exchange, to determine whether NSA-OBS was a sink/source in a given year, etc, it was calculated for all the periods in which we had data.
      Also note that the times in the derived data set do not match the measured data (Tower Flux, Meteorological, Soil Temperature Data) exactly in 1998. This is due to a problem with the time-matching program that caused some of the records to repeat the times in the 1998 processing. The derived data set was created before this problem was corrected and the derived data have not been reprocessed yet, although the measured data have. An update to the derived data will be placed on the Harvard web site sometime in the summer or fall of 2001.

6.2 Field Notes
      Notable data gaps occurred during the following periods:

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7. Data Description

7.1 Spatial Characteristics
7.1.1 Spatial Coverage
      All data were collected at the BOREAS NSA-OBS site. The site is located at 55.88007° N latitude, 98.48139° W longitude, at an elevation of 259 meters.

7.1.2 Spatial Coverage Map
      Not applicable.

7.1.3 Spatial Resolution
      The data represent point source measurements taken at the given location. The location and size of the footprint from which the measurements were made varied with ambient meteorological conditions.

7.1.4 Projection
      Not applicable.

7.1.5 Grid Description
      Not applicable.


7.2 Temporal Characteristics

7.2.1 Temporal Coverage
      The derived variables described here are available from March 1994 through the end of 1998. FLX-01 efforts at the NSA-OBS site are ongoing however, and additional data may be available from their web site.
      Valid measurements are available 72% of the time. Notable gaps occurred in May 1994, August 1994, fall 1994, June 1995, and November 1995.

7.2.2 Temporal Coverage Map
      Not available.

7.2.3 Temporal Resolution
      The derived parameters were calculated at 30-minute intervals from 1994-1998. Daily mean and sum values were calculated from 4 and 5 day averages, longer where data gaps occur.


7.3 Data Characteristics

7.3.1 Parameter/Variable
     The parameters contained in the data files are:
FLX01_DERIVED_30MIN_DATA
         Column Name
------------------------------
SITE_NAME
DATE_OBS
TIME_OBS
RESPIRATION
NEE
GEE
CRTFCN_CODE
REVISION_DATE

FLX01_BINNED_GEE_DATA
         Column Name
------------------------------
SITE_NAME
DATE_MIDPOINT
NUM_DAYS
MEAN_GEE_30MIN
MEAN_GEE_DAILY_SUM
SUM_GEE
CUM_GEE
CRTFCN_CODE
REVISION_DATE

FLX01_BINNED_NEE_DATA
         Column Name
------------------------------
SITE_NAME
DATE_MIDPOINT
NUM_DAYS
MEAN_NEE_30MIN
MEAN_NEE_DAILY_SUM
SUM_NEE
CUM_NEE
CRTFCN_CODE
REVISION_DATE

FLX01_BINNED_RESPIRATION_DATA
         Column Name
------------------------------
SITE_NAME
DATE_MIDPOINT
NUM_DAYS
MEAN_RESPIRATION_30MIN
MEAN_RESPIRATION_DAILY_SUM
SUM_RESPIRATION
CUM_RESPIRATION
CRTFCN_CODE
REVISION_DATE

7.3.2 Variable Description/Definition
     The descriptions of the parameters contained in the data files are:
FLX01_DERIVED_30MIN_DATA
         Column Name                             Description
------------------------------ ------------------------------------------------
SITE_NAME                      The identifier assigned to the site by BOREAS, in
                               the format SSS-TTT-CCCCC, where SSS identifies
                               the portion of the study area: NSA, SSA, REG,
                               TRN, and TTT identifies the cover type for the
                               site, 999 if unknown, and CCCCC is the identifier
                               for site, exactly what it means will vary with
                               site type.
DATE_OBS                       The date on which the data were collected.
TIME_OBS                       The mid-point of the 30-min data collection
                               period, in Greenwich Mean Time (GMT).
RESPIRATION                    Respiration of CO2.
NEE                            The net ecosystem exchange of carbon.
GEE                            The gross ecosystem exchange of carbon,
                               calculated by subtracting Respiration from NEE.
CRTFCN_CODE                    The BOREAS certification level of the data.
                               Examples are CPI (Checked by PI), CGR (Certified
                               by Group), PRE (Preliminary), and CPI-??? (CPI
                               but questionable).
REVISION_DATE                  The most recent date when the information in the
                               referenced data base table record was revised.

FLX01_BINNED_GEE_DATA
         Column Name                             Description
------------------------------ ------------------------------------------------
SITE_NAME                      The identifier assigned to the site by BOREAS, in
                               the format SSS-TTT-CCCCC, where SSS identifies
                               the portion of the study area: NSA, SSA, REG,
                               TRN, and TTT identifies the cover type for the
                               site, 999 if unknown, and CCCCC is the identifier
                               for site, exactly what it means will vary with
                               site type.
DATE_MIDPOINT                  The temporal midpoint of the time period bin
                               defined by NUM_DAYS.
NUM_DAYS                       The number of days in the time period bin for the
                               measurements, centered on the DATE_MIDPOINT.
MEAN_GEE_30MIN                 The mean half-hour gross ecosystem exchange of
                               carbon within the time period defined by
                               DATE_MIDPOINT and NUM_DAYS.
MEAN_GEE_DAILY_SUM             The mean of the daily sum (sum of the 48 half-
                               hour periods) of gross ecosystem exchange of
                               carbon measurements for the time period defined
                               by DATE_MIDPOINT and NUM_DAYS.
SUM_GEE                        The sum gross ecosystem exchange of carbon for
                               the time period defined by DATE_MIDPOINT and
                               NUM_DAYS, calculated as the MEAN_GEE_DAILY_SUM
                               multiplied by NUM_DAYS.
CUM_GEE                        The cumulative gross ecosystem exchange of carbon
                               from day one of data collection (01-Jan-1994) to
                               the date defined by DATE_MIDPOINT and NUM_DAYS.
CRTFCN_CODE                    The BOREAS certification level of the data.
                               Examples are CPI (Checked by PI), CGR (Certified
                               by Group), PRE (Preliminary), and CPI-??? (CPI
                               but questionable).
REVISION_DATE                  The most recent date when the information in the
                               referenced data base table record was revised.

FLX01_BINNED_NEE_DATA
         Column Name                             Description
------------------------------ ------------------------------------------------
SITE_NAME                      The identifier assigned to the site by BOREAS, in
                               the format SSS-TTT-CCCCC, where SSS identifies
                               the portion of the study area: NSA, SSA, REG,
                               TRN, and TTT identifies the cover type for the
                               site, 999 if unknown, and CCCCC is the identifier
                               for site, exactly what it means will vary with
                               site type.
DATE_MIDPOINT                  The temporal midpoint of the time period bin
                               defined by NUM_DAYS.
NUM_DAYS                       The number of days in the time period bin for the
                               measurements, centered on the DATE_MIDPOINT.
MEAN_NEE_30MIN                 The mean half-hour net ecosystem exchange of
                               carbon within the time period defined by
                               DATE_MIDPOINT and NUM_DAYS.
MEAN_NEE_DAILY_SUM             The mean of the daily sum (sum of the 48 half-
                               hour periods) of net ecosystem exchange of carbon
                               measurements for the time period defined by
                               DATE_MIDPOINT and NUM_DAYS.
SUM_NEE                        The sum net ecosystem exchange of carbon for the
                               time period defined by DATE_MIDPOINT and
                               NUM_DAYS, calculated as the MEAN_NEE_DAILY_SUM
                               multiplied by NUM_DAYS.
CUM_NEE                        The cumulative net ecosystem exchange of carbon
                               from day one of data collection (01-Jan-1994) to
                               the date defined by DATE_MIDPOINT and NUM_DAYS.
CRTFCN_CODE                    The BOREAS certification level of the data.
                               Examples are CPI (Checked by PI), CGR (Certified
                               by Group), PRE (Preliminary), and CPI-??? (CPI
                               but questionable).
REVISION_DATE                  The most recent date when the information in the
                               referenced data base table record was revised.

FLX01_BINNED_RESPIRATION_DATA
         Column Name                             Description
------------------------------ ------------------------------------------------
SITE_NAME                      The identifier assigned to the site by BOREAS, in
                               the format SSS-TTT-CCCCC, where SSS identifies
                               the portion of the study area: NSA, SSA, REG,
                               TRN, and TTT identifies the cover type for the
                               site, 999 if unknown, and CCCCC is the identifier
                               for site, exactly what it means will vary with
                               site type.
DATE_MIDPOINT                  The temporal midpoint of the time period bin
                               defined by NUM_DAYS.
NUM_DAYS                       The number of days in the time period bin for the
                               measurements, centered on the DATE_MIDPOINT.
MEAN_RESPIRATION_30MIN         The mean half-hour CO2 respiration within the
                               time period defined by DATE_MIDPOINT and
                               NUM_DAYS.
MEAN_RESPIRATION_DAILY_SUM     The mean of the daily sum (sum of the 48 half-
                               hour periods) of CO2 respiration measurements
                               for the time period defined by DATE_MIDPOINT
                               and NUM_DAYS.
SUM_RESPIRATION                The sum CO2 respiration for the time period
                               defined by DATE_MIDPOINT and NUM_DAYS, calculated
                               as the MEAN_NEE_DAILY_SUM multiplied by NUM_DAYS.
CUM_RESPIRATION                The cumulative CO2 respiration from day one of
                               data collection (01-Jan-1994) to the date defined
                               by DATE_MIDPOINT and NUM_DAYS.
CRTFCN_CODE                    The BOREAS certification level of the data.
                               Examples are CPI (Checked by PI), CGR (Certified
                               by Group), PRE (Preliminary), and CPI-??? (CPI
                               but questionable).
REVISION_DATE                  The most recent date when the information in the
                               referenced data base table record was revised.

7.3.3 Unit of Measurement
     The measurement units for the parameters contained in the data files are:
FLX01_DERIVED_30MIN_DATA
         Column Name                                Units
------------------------------ ------------------------------------------------
SITE_NAME                      [none]
DATE_OBS                       [DD-MON-YY]
TIME_OBS                       [HHMM GMT]
RESPIRATION                    [micromoles][meters^-2][second^-1]
NEE                            [micromoles][meters^-2][second^-1]
GEE                            [micromoles][meters^-2][second^-1]
CRTFCN_CODE                    [none]
REVISION_DATE                  [DD-MON-YY]

FLX01_BINNED_GEE_DATA
         Column Name                                Units
------------------------------ ------------------------------------------------
SITE_NAME                      [none]
DATE_MIDPOINT                  [DD-MON-YY]
NUM_DAYS                       [days]
MEAN_GEE_30MIN                 [kilograms Carbon][hectare^-1][30 minutes^-1]
MEAN_GEE_DAILY_SUM             [kilograms Carbon][hectare^-1][day^-1]
SUM_GEE                        [kilograms Carbon][hectare^-1]
CUM_GEE                        [kilograms Carbon][hectare^-1]
CRTFCN_CODE                    [none]
REVISION_DATE                  [DD-MON-YY]

FLX01_BINNED_NEE_DATA
         Column Name                                Units
------------------------------ ------------------------------------------------
SITE_NAME                      [none]
DATE_MIDPOINT                  [DD-MON-YY]
NUM_DAYS                       [days]
MEAN_NEE_30MIN                 [kilograms Carbon][hectare^-1][30 minutes^-1]
MEAN_NEE_DAILY_SUM             [kilograms Carbon][hectare^-1][day^-1]
SUM_NEE                        [kilograms Carbon][hectare^-1]
CUM_NEE                        [kilograms Carbon][hectare^-1]
CRTFCN_CODE                    [none]
REVISION_DATE                  [DD-MON-YY]

FLX01_BINNED_RESPIRATION_ DATA
         Column Name                                Units
------------------------------ ------------------------------------------------
SITE_NAME                      [none]
DATE_MIDPOINT                  [DD-MON-YY]
NUM_DAYS                       [days]
MEAN_RESPIRATION_30MIN         [kilograms Carbon][hectare^-1][30 minutes^-1]
MEAN_RESPIRATION_DAILY_SUM     [kilograms Carbon][hectare^-1][day^-1]
SUM_RESPIRATION                [kilograms Carbon][hectare^-1]
CUM_RESPIRATION                [kilograms Carbon][hectare^-1]
CRTFCN_CODE                    [none]
REVISION_DATE                  [DD-MON-YY]

7.3.4 Data Source
     The source of the parameter values contained in the data are:
FLX01_DERIVED_30MIN_DATA
         Column Name                    Data Source
------------------------------ ------------------------------------------------
SITE_NAME                      [BORIS Designation]
DATE_OBS                       [Datalogger]
TIME_OBS                       [Datalogger]
RESPIRATION                    [Calculated value]
NEE                            [Calculated value]
GEE                            [Calculated value]
CRTFCN_CODE                    [BORIS Designation]
REVISION_DATE                  [BORIS Designation]

FLX01_BINNED_GEE_DATA
         Column Name                    Data Source
------------------------------ ------------------------------------------------
SITE_NAME                      [BORIS Designation]
DATE_MIDPOINT                  [Calculated Value]
NUM_DAYS                       [Calculated Value]
MEAN_GEE_30MIN                 [Calculated value]
MEAN_GEE_DAILY_SUM             [Calculated value]
SUM_GEE                        [Calculated Value]
CUM_GEE                        [Calculated Value]
CRTFCN_CODE                    [BORIS Designation]
REVISION_DATE                  [BORIS Designation]

FLX01_BINNED_NEE_DATA
         Column Name                    Data Source
------------------------------ ------------------------------------------------
SITE_NAME                      [BORIS Designation]
DATE_MIDPOINT                  [Calculated Value]
NUM_DAYS                       [Calculated Value]
MEAN_NEE_30MIN                 [Calculated value]
MEAN_NEE_DAILY_SUM             [Calculated value]
SUM_NEE                        [Calculated Value]
CUM_NEE                        [Calculated Value]
CRTFCN_CODE                    [BORIS Designation]
REVISION_DATE                  [BORIS Designation]

FLX01_BINNED_RESPIRATION_DATA
         Column Name                    Data Source
------------------------------ ------------------------------------------------
SITE_NAME                      [BORIS Designation]
DATE_MIDPOINT                  [Calculated Value]
NUM_DAYS                       [Calculated Value]
MEAN_RESPIRATION_30MIN         [Calculated value]
MEAN_RESPIRATION_DAILY_SUM     [Calculated value]
SUM_RESPIRATION                [Calculated Value]
CUM_RESPIRATION                [Calculated Value]
CRTFCN_CODE                    [BORIS Designation]
REVISION_DATE                  [BORIS Designation]

7.3.5 Data Range
     The following table gives information about the parameter values found in the data files.
FLX01_DERIVED_30MIN_DATA
                     Minimum        Maximum        Missng  Unrel  Below   Data
                     Data           Data           Data    Data   Detect  Not
Column Name          Value          Value          Value   Value  Limit   Cllctd
--------------------------------------------------------------------------------
SITE_NAME            NSA-OBS-FLXTR  NSA-OBS-FLXTR  None    None   None    None
DATE_OBS             17-MAR-94      31-DEC-98      None    None   None    None
TIME_OBS             0              2330           None    None   None    None
RESPIRATION          -4.716         29.831         -999    None   None    None
NEE                  -18.733        45.108         -999    None   None    None
GEE                  -25.86         25.279         -999    None   None    None
CRTFCN_CODE          CPI            CPI            None    None   None    None
REVISION_DATE        21-OCT-99      21-OCT-99      None    None   None    None

FLX01_BINNED_GEE_DATA
                     Minimum        Maximum        Missng  Unrel  Below   Data
                     Data           Data           Data    Data   Detect  Not
Column Name          Value          Value          Value   Value  Limit   Cllctd
--------------------------------------------------------------------------------
SITE_NAME            NSA-OBS-FLXTR  NSA-OBS-FLXTR  None    None   None    None
DATE_MIDPOINT        30-OCT-94      26-OCT-97      None    None   None    None
NUM_DAYS             3              37             None    None   None    None
MEAN_GEE_30MIN       -1.7585        .1065          None    None   None    None
MEAN_GEE_DAILY_SUM   -84.41         5.1105         None    None   None    None
SUM_GEE              -948.9233      20.442         None    None   None    None
CUM_GEE              -23363.816     86.6358        None    None   None    None
CRTFCN_CODE          CPI            CPI            None    None   None    None
REVISION_DATE        25-OCT-99      25-OCT-99      None    None   None    None

FLX01_BINNED_NEE_DATA
                     Minimum        Maximum        Missng  Unrel  Below   Data
                     Data           Data           Data    Data   Detect  Not
Column Name          Value          Value          Value   Value  Limit   Cllctd
--------------------------------------------------------------------------------
SITE_NAME            NSA-OBS-FLXTR  NSA-OBS-FLXTR  None    None   None    None
DATE_MIDPOINT        19-MAR-94      03-DEC-98      None    None   None    None
NUM_DAYS             4              50             None    None   None    None
MEAN_NEE_30MIN       -.516          .5336          None    None   None    None
MEAN_NEE_DAILY_SUM   -24.7677       25.6134        None    None   None    None
SUM_NEE              -366.6968      176.6758       None    None   None    None
CUM_NEE              -716.1888      714.6692       None    None   None    None
CRTFCN_CODE          CPI            CPI            None    None   None    None
REVISION_DATE        26-OCT-99      26-OCT-99      None    None   None    None

FLX01_BINNED_RESPIRATION_DATA
                     Minimum        Maximum        Missng  Unrel  Below   Data
                     Data           Data           Data    Data   Detect  Not
Column Name          Value          Value          Value   Value  Limit   Cllctd
--------------------------------------------------------------------------------
SITE_NAME            NSA-OBS-FLXTR  NSA-OBS-FLXTR  None    None   None    None
DATE_MIDPOINT        30-OCT-94      24-OCT-97      None    None   None    None
NUM_DAYS             4              24             None    None   None    None
MEAN_RESPIRATION_    -.0058         2.3836         None    None   None    None
30MIN
MEAN_RESPIRATION_     -.2788         114.4147       None    None   None    None
DAILY_SUM
SUM_RESPIRATION      -1.1152        845.9633       None    None   None    None
CUM_RESPIRATION      10.1768        24185.4565     None    None   None    None
CRTFCN_CODE          CPI            CPI            None    None   None    None
REVISION_DATE        25-OCT-99      25-OCT-99      None    None   None    None

--------------------------------------------------------------------------------
Minimum Data Value -- The minimum value found in the column.
Maximum Data Value -- The maximum value found in the column.
Missng Data Value  -- The value that indicates missing data. This is used to
                      indicate that an attempt was made to determine the
                      parameter value, but the attempt was unsuccessful.
Unrel Data Value   -- The value that indicates unreliable data.  This is used
                      to indicate an attempt was made to determine the
                      parameter value, but the value was deemed to be
                      unreliable by the analysis personnel.
Below Detect Limit -- The value that indicates parameter values below the
                      instruments detection limits.  This is used to
                      indicate that an attempt was made to determine the
                      parameter value, but the analysis personnel determined
                      that the parameter value was below the detection
                      limit of the instrumentation.
Data Not Cllctd    -- This value indicates that no attempt was made to
                      determine the parameter value.  This usually
                      indicates that BORIS combined several similar but
                      not identical data sets into the same data base table
                      but this particular science team did not
                      measure that parameter.

Blank -- Indicates that blank spaces are used to denote that type of value.
N/A   -- Indicates that the value is not applicable to the respective column.
None  -- Indicates that no values of that sort were found in the column.
--------------------------------------------------------------------------------


7.4 Sample Data Record
     The following are wrapped versions of data record from a sample data file:

FLX01_DERIVED_30MIN_DATA
SITE_NAME,SUB_SITE,DATE_OBS,TIME_OBS,RESPIRATION,NEE,GEE,CRTFCN_CODE,
REVISION_DATE
'NSA-OBS-FLXTR','FLX01-FLX01',17-MAR-94,330,-999.0,.08,0.0,'CPI',21-OCT-99
'NSA-OBS-FLXTR','FLX01-FLX01',17-MAR-94,400,-999.0,.08,0.0,'CPI',21-OCT-99

FLX01_BINNED_GEE_DATA
SITE_NAME,DATE_MIDPOINT,NUM_DAYS,MEAN_GEE_30MIN,MEAN_GEE_DAILY_SUM,SUM_GEE,
CUM_GEE,CRTFCN_CODE,REVISION_DATE
'NSA-OBS-FLXTR',30-Oct-94,4,0.1065,5.1105,20.442,20.442,'CPI',25-Oct-99
'NSA-OBS-FLXTR',3-Nov-94,4,0.0844,4.0533,16.2132,36.6552,'CPI',25-Oct-99

FLX01_BINNED_NEE_DATA
SITE_NAME,DATE_MIDPOINT,NUM_DAYS,MEAN_NEE_30MIN,MEAN_NEE_DAILY_SUM,SUM_NEE,
CUM_NEE,CRTFCN_CODE,REVISION_DATE
'NSA-OBS-FLXTR',5-Jan-95,8,0.0395,1.8969,15.1752,15.1752,'CPI',26-Oct-99
'NSA-OBS-FLXTR',11-Jan-95,4,0.0417,2.0013,8.0052,23.1804,'CPI',26-Oct-99

FLX01_BINNED_RESPIRATION_DATA
SITE_NAME,DATE_MIDPOINT,NUM_DAYS,MEAN_RESPIRATION_30MIN,MEAN_RESPIRATION_DAILY_SUM,
SUM_RESPIRATION,CUM_RESPIRATION,CRTFCN_CODE,REVISION_DATE
'NSA-OBS-FLXTR',1-Jan-97,4,0.0694,3.3299,13.3196,16863.6155,'CPI',25-Oct-99
'NSA-OBS-FLXTR',5-Jan-97,4,0.0322,1.547,6.188,16869.8035,'CPI',25-Oct-99
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8. Data Organization

8.1 Data Granularity
      The 30-minute derived data files each contain measurements of Respiration, NEE, and GEE and are organized by year. Multi-day binned data have separate files for derived GEE, NEE, and Respiration.

8.2 Data Format
      The data file contains numerical and character fields of varying length separated by commas. Character fields are enclosed with single apostrophe marks. There are no spaces between the fields.
 

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9. Data Manipulations

9.1 Formulae
      None.
9.1.1 Derivation Techniques and Algorithms
      The algorithms are sophisticated and derived from well-proven processing software. Further discussion can be found in Goulden et al. 1996.


9.2 Data Processing Sequence

9.2.1 Processing Steps
  1. Data are extracted from CR-10 binary into three large ASCII files of raw data.
  2. Calibration information is extracted from the raw data files and the calibration coefficients are calculated using the concentration values (which change when gas cylinders are changed).
  3. Covariances are calculated from the raw data, taking into account smearing and applying the corrections needed to compensate for the damping of high-frequency fluctuations.
  4. Fluxes are calculated from the covariances and the amount of spiking exhibited by the sonic anemometer is determined. If there is excessive spiking (indicating rain or extremely cold temperatures) the data are discarded.
  5. Storage is calculated using the profile CO2 concentration data.
This processing then yields the data files that we use to calculate the derived data (using the relationships described in section 1.5).

9.2.2 Processing Changes
      None.


9.3 Calculations

9.3.1 Special Corrections/Adjustments
      The sonic anemometer occasionally developed spiking problemsy, caused either by precipitation or by malfunctioning transducers. Processing code was adapted to determine the number of spikes in each interval and to recalculate the turbulent fluxes after filtering out these spikes.
      NEE is replaced with the calculated respiration during non-windy nights, as the atmosphere is not well mixed and the tower measurements are less accurate. Missing daytime GEE is calculated during the summer based on the amount of photosythetically active radiation. The missing NEE data during summer days are approximated by adding this interpolated GEE data to the calculated Respiration.

9.3.2 Calculated Variables
      Eddy CO2 flux is used to calculate NEE (net ecosystem exchange). Respiration is determined based on NEE measurements during windy nights using a temperature relationship. GEE (gross ecosystem exchange) is then calculated by subtracting respiration from NEE.


9.4 Graphs and Plots
      None.

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10. Errors

10.1 Sources of Error
      Errors in flux measurements may be associated with wind from behind the tower, calm conditions, and the damping of high-frequency fluctuations. The sonic anemometer occasionally developed problems with spiking, caused either by precipitation, or by malfunctioning transducers.

10.2 Quality Assessment

10.2.1 Data Validation by Source
      Raw flux data were examined for errors associated with wind from behind the tower, calm conditions, the damping of high-frequency fluctuations, and for intervals with malfunctioning instruments. These periods were excluded or the errors were corrected.

10.2.2 Confidence Level/Accuracy Judgment
      None given.

10.2.3 Measurement Error for Parameters
      None given.

10.2.4 Additional Quality Assessments
      None given.

10.2.5 Data Verification by Data Center
      Data were examined to check for spikes, values that are four standard deviations from the mean, long periods of constant values, and missing data.

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11. Notes

11.1 Limitations of the Data
      None given.

11.2 Known Problems with the Data
      CO2 fluxes may be underestimated when the friction velocity is less than 0.2 m/sec. The closed-path IRGA and long sampling tube resulted in an underestimation of water vapor and CO2 flux because of the damping of high-frequency fluctuations.

11.3 Usage Guidance
      The FLX-01 team wishes that those planning to use their data to please contact the Harvard group (see section 2.3) first.

11.4 Other Relevant Information
      A wide range of other useful data such as soil temperature, Photosynthetically Active Radiation (PAR), net radiation, momentum flux, etc., are also available at ftp://ftp.as.harvard.edu/pub/nigec/Boreas_OBS/ [Internet Link].

Especially note CO2 profiles hourly.

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12. Application of the Data Set

This data set is useful for studying the NEE, GEE, and respiration annual and inter-annual relationships for NSA-OBS from 1994 through 1998.

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13. Future Modifications and Plans

The derived data sets include corrections for "lost flux" under conditions of low wind speed. We have made those corrections as best we know how to do. There are however several interesting ideas for more rigorous treatment of flux at low u*, and should any of these work out well then the data would change.

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14. Software

14.1 Software Description
      None given.

14.2 Software Access
      None given.

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15. Data Access

15.1 Contact for Data Center/Data Access Information
      These BOREAS Follow-On data are available from the Earth Observing System Data and Information System (EOS-DIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The contact at ORNL is:

ORNL DAAC User Services
Oak Ridge National Laboratory
(865) 241-3952
ornldaac@ornl.gov
ornl@eos.nasa.gov

15.2 Procedures for Obtaining Data
      Data may be obtained through the ORNL DAAC World Wide Web site at http://daac.ornl.gov/ [Internet Link] or users may place requests for data by telephone or electronic mail.

15.3 Output Products and Availability
      Requested data can be provided electronically on the ORNL DAAC's anonymous FTP site or on various media including, CD-ROMs, 8-MM tapes, or diskettes.

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16. Output Products and Availability

16.1 Tape Products
      None.

16.2 Film Products
      None.

16.3 Other Products
      None.

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17. References

17.1 Platform/Sensor/Instrument/Data Processing Documentation
LI-COR 1991. LI-6262 CO2/H2O analyzer operating and service manual. Publ. 9003-59, Linclon,NE.
 

17.2 Journal Articles and Study Reports
Goulden, M.L., J.W. Munger, S.M. Fan, B.C. Daube, and S.C. Wofsy. 1996. Measurements of carbon storage by long-term eddy correlation: Methods and a critical evaluation of accuracy, Global Change Biology 2 (3),169-182.

Goulden, M.L., B.C. Daube, S.M. Fan, D.J. Sutton, A. Bazzaz, J.W. Munger, and S.C. Wofsy. 1997. Physiological responses of a black spruce forest to weather, Journal of Geophysical Research 102 (D24):28987,28996.

Goulden, M.L., S.C. Wofsy, J.W. Harden, S.E. Trumbore, P.M. Crill, S.T. Gower, T. Fries, B.C. Daube, S.M. Fan, D.J. Sutton, A. Bazzaz, and J.W. Munger, Sensitivity of Boreal Forest Carbon Balance to Soil Thaw, Science 279, 9 January 1998: 214-217.

Kaimal, J.C. and J.E. Gaynor. 1991. Another look at sonic thermometry. Boundary Layer Meteorology. 56:401-410.

Kaimal, J.C., J.E. Gaynor, H.A. Zimmerman, and G.A. Zimmerman. 1990. Minimizing flow distortion errors in a sonic anemometer. Boundary Layer Meteorology. 53:103-115.

Schotanus, P., F.T.M. Nieuwstadt, and H.A.R. De Bruin. 1983. Temperature measurement with a sonic anemometer and its application to heat and moisture fluxes. Boundary-Layer Meteorology. 26: 81-93.

Sellers, P. and F. Hall. 1994. Boreal Ecosystem-Atmosphere Study: Experiment Plan. Version 1994-3.0, NASA BOREAS Report (EXPLAN 94).

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, and K.F. Huemmrich. 1996. Boreal Ecosystem-Atmosphere Study: 1994 Operations. NASA BOREAS Report (OPS DOC 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. 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, and F.E. Guertin. 1997. BOREAS in 1997: Experiment overview, scientific results, and future directions. Journal of Geophysical Research. 102(D24):28731-28770.
 

17.3 Archive/DBMS Usage Documentation
      None.

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18. Glossary of Terms

None.

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19. List of Acronyms

    ASCII   - American Standard Code for Information Interchange
    BOREAS  - BOReal Ecosystem-Atmosphere Study
    BORIS   - BOREAS Information System
    DAAC    - Distributed Active Archive Center
    EOS     - Earth Observing System
    EOSDIS  - EOS Data and Information System
    GMT     - Greenwich Mean Time
    GSFC    - Goddard Space Flight Center
    IRGA    - Infrared Gas Analyzer
    NASA    - National Aeronautics and Space Administration
    NSA     - Northern Study Area
    OBS     - Old Black Spruce
    ORNL    - Oak Ridge National Laboratory
    PANP    - Prince Albert National Park
    PAR     - Photosynthetically Active Radiation
    SSA     - Southern Study Area
    PPFD    - Photosynthetic Photon Flux Density
    URL     - Uniform Resource Locator
    WMO     - World Meteorological Organization
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20. Document Information

20.1 Document Revision Date

Written: 29-Sep-1999
Revised: 27-Apr-2001 (citation revised on 30-Oct-2002)

20.2 Document Review Date(s)

      BORIS Review: 15-Feb-2000
      Science Review:

20.3 Document ID

flx01_derived

20.4 Citation

Cite this data set as follows (citation revised on October 30, 2002):

Wofsy, S. C., and A. Dunn. 2001. BOREAS Follow-On FLX-01 NSA-OBS Derived Data - NEE, GEE, and Respiration. Data set. Available on-line [http://www.daac.ornl.gov] from Oak Ridge National Laboratory Distributed Active Archive Center, Oak Ridge, Tennessee, U.S.A.

20.5 Document Curator:

webmaster@daac.ornl.gov

20.6 Document URL:

http://daac.ornl.gov/BOREAS/FollowOn/guides/flx01_all_derived_doc.html

Keywords
BLACK SPRUCE
CARBON DIOXIDE FLUX
GEE
GROSS ECOSYSTEM EXCHANGE
NEE
NET ECOSYSTEM EXCHANGE
PHOTOSYNTHETICALLY ACTIVE RADIATION
RESPIRATION
TOWER FLUX

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