Data Checks and Processing Performed by CDIAC

An important part of the numeric data packaging 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 Knorr cruise along WOCE Sections AR24, A24, A20, and A22 in the North Atlantic Ocean.

1. The final carbon-related data were provided to CDIAC by the ocean carbon measurement PI principal investigators listed in cruise information section. 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.
2. Every measured parameter for each station was plotted vs depth (pressure) to identify questionable data points using the Ocean Data View (ODV) software (Schlitzer 2001) Station Mode (Fig. 5).
3. Section plots for every parameter were generated using ODVs Section Mode in order to map a general distribution of each property along all North Atlantic Ocean sections (Fig. 6).
4. To identify "noisy" data and possible systematic, methodological errors, property-property plots for all parameters were generated (Fig. 7), carefully examined, and compared with plots from previous expeditions in the North Atlantic Ocean.
5. All variables were checked for values exceeding physical limits, such as sampling depth values that are greater than the given bottom depths.
6. Dates, times, and coordinates were checked for bogus values (e.g., values of MONTH < 1 or > 12; DAY < 1 or > 31; YEAR < 1996 or > 1997; TIME < 0000 or > 2400; LATITUDE < 7.000 or > 67.000; LONGITUDE < -68.000 or > -8.000.
7. Station locations (latitudes and longitudes) and sampling times were examined for consistency with maps and cruise information supplied by PIs.
8. The designation for missing values, given as -9.0 in the original files, was changed to -999.9 for the consistency with other oceanographic data sets.