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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
- Data Set Overview
- Investigator(s)
- Theory of Measurements
- Equipment
- Data Acquisition Methods
- Observations
- Data Description
- Data Organization
- Data Manipulations
- Errors
- Notes
- Application of the Data Set
- Future Modifications and Plans
- Software
- Data Access
- Output Products and Availability
- References
- Glossary of Terms
- List of Acronyms
- Document Information
1. Data Set Overview
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
2. Investigator(s)
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
3. Theory of Measurements
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.
4. Equipment
4.1.1 Collection Environment4.2 Calibration
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 logger4.1.3 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, GEE4.1.5 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 80301-3390Campbell Scientific Instruments
P.O. Box 551
Logan, UT 84321LiCor
P.O. Box 4425
Lincoln, NE 68504-0425MKS Instruments
6 Shattuck Rd
Andover, MA 01810-2495
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
6. Observations
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:
- May 1994, when an error was introduced into the data acquisition code.
- August 1994, when the sonic anemometer was damaged twice by lightning.
- Fall 1994, when the generator failed repeatedly.
- June 1995, when computer disks failed twice.
- November 1995, when the sonic anemometer failed with the onset of cold temperatures.
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7. Data Description
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_DATE7.3.2 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
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.
9. Data Manipulations
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 StepsThis processing then yields the data files that we use to calculate the derived data (using the relationships described in section 1.5).
- Data are extracted from CR-10 binary into three large ASCII files of raw data.
- 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).
- 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.
- 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.
- Storage is calculated using the profile CO2 concentration data.
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.
10. Errors
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
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.
12. Application of the Data Set
13. Future Modifications and Plans
14. Software
None given.
14.2 Software Access
None given.
15. Data Access
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.
16. Output Products and Availability
None.
16.2 Film Products
None.
16.3 Other Products
None.
17. References
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.
18. Glossary of Terms
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-1999Revised: 27-Apr-2001 (citation revised on 30-Oct-2002)
20.2 Document Review Date(s)
BORIS Review: 15-Feb-2000Science Review:
20.3 Document ID
flx01_derived20.4 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.gov20.6 Document URL:
http://daac.ornl.gov/BOREAS/FollowOn/guides/flx01_all_derived_doc.htmlKeywords
BLACK SPRUCE
CARBON DIOXIDE FLUX
GEE
GROSS ECOSYSTEM EXCHANGE
NEE
NET ECOSYSTEM EXCHANGE
PHOTOSYNTHETICALLY ACTIVE RADIATION
RESPIRATION
TOWER FLUX