Data Checks and Processing Performed by CDIAC
An important part of the NDP process at the Carbon Dioxide Information Analysis Center (CDIAC) involves the quality assurance (QA) of data before distribution. Data received at CDIAC are rarely in a condition that would permit immediate distribution, regardless of the source. To guarantee data of the highest possible quality, CDIAC conducts extensive QA reviews that involve examining the data for completeness, reasonableness, and accuracy. The QA process is a critical component in the value-added concept of supplying accurate, usable data for researchers.
The following information summarizes the data processing and QA checks performed by CDIAC on the data obtained during the R/V Thomas G. Thompson cruise along WOCE Section P10 in the Pacific Ocean.
- The final carbon-related data and radiocarbon measurements were provided to CDIAC by Chris Sabine and Bob Key of Princeton University. The final hydrographic and chemical measurements and the station information files were provided by the WOCE Hydrographic Program Office (WHPO) after quality evaluation. A FORTRAN 90 retrieval code was written and used to merge and reformat all data files.
- To check for obvious outliers, all data were plotted by use of a PLOTNEST.C program written by Stewart C. Sutherland (Lamont-Doherty Earth Observatory). The program plots a series of nested profiles, using the station number as an offset; the first station is defined at the beginning, and subsequent stations are offset by a fixed interval (Fig. 15 and Fig. 16). Several outliers were identified and marked with the quality flags of "3" (questionable measurement) or "4" (bad measurement) (see File Descriptions in Part 2 of this documentation).
- To identify "noisy" data and possible systematic, methodological errors, property-property plots for all parameters were generated (Fig. 17), carefully examined, and compared with plots from previous expeditions in the Pacific Ocean.
- All variables were checked for values exceeding physical limits, such as sampling depth values that are greater than the given bottom depths.
- Dates, times, and coordinates were checked for bogus values (e.g., values of MONTH < 1 or > 12; DAY < 1 or > 31; YEAR < or > 1993; TIME < 0000 or > 2400; LAT < 10.000 or > 40.000; and LONG < 140.000 or > 180.000).
- Station locations (latitudes and longitudes) and sampling times were examined for consistency with maps and cruise information supplied by C. Sabine and R. Key of Princeton University.
- The designation for missing values, given as -9.0 in the original files, was changed to -999.9.