Data from the Tracing Radiation and Architecture of Canopies (TRAC) instrument were processed to determine the fraction of intercepted photosynthetically active radiation (FPAR) at the EOS Validation Core Site in Kataba Local Forest, approximately 20 km south of Mongu, Zambia. Measurements began in 1999 and continued into 2002, with measurements collected about every month.
TRAC contains three pyranometers sensitive to PAR wavelengths, with two sensors upward looking and one downward looking. The TRAC instrument was carried along three parallel transects, each 750 m long and spaced 250 m apart, at a steady pace about 0.7 m off the ground on clear days near midday. The sensors measured PAR at 32 Hz, resulting in a horizontal sampling interval of about 1.7 cm (Privette et al., 2002). Each transect was divided into 25-m segments, and FPAR values, with date/time stamp, are reported for each segment. The length and spacing of the transects were chosen to sample an area large enough to be representative of a 1-km MODIS pixel.
PAR transmittance values were determined from the upward-viewing pyranometers on the TRAC instrument. Because of the large gaps in the canopy, incident PAR was estimated from the TRAC data as 95% of the maximum PAR transmittance value for each transect. The FPAR values of all the observations were averaged to give segment-average FPAR, and segment-average FPAR values were averaged to give transect-average FPAR.
The data are stored in an ASCII text file, in comma-separated-value (csv) format, with column headers.
Cite this data set as follows:
Privette, J. L., M. M. Mukelabai, and K. F. Huemmrich. 2005. SAFARI 2000 FPAR TRAC Data for Mongu, Zambia, 1999-2002. Data set. Available on-line [http://daac.ornl.gov/] from Oak Ridge National Laboratory Distributed Active Archive Center, Oak Ridge, Tennessee, U.S.A. doi:10.3334/ORNLDAAC/784.
Privette, J. L., R. B. Myneni, Y. Knyazikhin, M. Mukufute, G. Roberts, Y. Tian, Y. Wang, and S. G. Leblanc. 2002. Early spatial and temporal validation of MODIS LAI product in Africa. Remote Sensing of Environment, 83(1-2): 232-243.
The data are stored in an ASCII text file, in comma-separated-value (csv) format, with column headers.
| Column Name | Definition | Units/Format |
|---|---|---|
| Transect | The Transect ID name: A, B, or C | ASCII |
| segment number | Within the transect, the 25 m long subdivision ID. Starting from the eastern transect end increasing as one goes west. If segment number is AVG values are summaries for the entire transect. | numeric |
| Date | The date of data collection | MM/DD/YY |
| START TIME | The starting time of data collection | HH:MM GMT |
| END TIME | The ending time of data collection | HH:MM GMT |
| NUM PTS | The number of data values collected | numeric |
| MIN VAL Trans PAR | The minimum value of PAR transmitted through the canopy | µmol m-2 s-1 |
| MAX VAL Trans PAR | The maximum value of PAR transmitted through the canopy | µmol m-2 s-1 |
| AVG Reflected PAR from Soil | The average value of PAR reflected from the background | µmol m-2 s-1 |
| Avg FPAR | The average FPAR | unitless |
| Data file | Original file name for raw TRAC data | ASCII |
| Notes | Further information about the data. If the direction of data collection is not given in this column, segment numbers were determined by comparing data with other transects. | ASCII |
Sample Data Records
Transect,segment number,Date,START TIME,END TIME,NUM PTS,MIN VAL Trans PAR,MAX VAL Trans PAR, AVG Reflected PAR from Soil,Avg FPAR,Data file,Notes A,30,3/29/01,10:15,10:16,1107,25,1737,51,0.6575,MT29031A.TRC,West to East A,29,3/29/01,10:17,10:17,1470,44,1720,43,0.6204,MT29031A.TRC,West to East A,28,3/29/01,10:17,10:18,629,187,1882,170,0.1009,MT29031A.TRC,West to East |
Additional information about the Mongu study site, data collection and processing, measurement theory, TRAC instrumentation, and data limitations or problems is found in the companion file: http://daac.ornl.gov/daacdata/safari2k/field_campaign/mongu_fpar_trac/comp/mongu_fpar_trac_readme.pdf.
2004/12/27
2004/12/27
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