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. Although they have common objectives, these reviews are tailored to each data set, often requiring extensive programming efforts. In short, the QA process is a critical component in the value-added concept of supplying accurate, usable data.

The following summarizes the data processing and QA checks performed by CDIAC on the data obtained during the R/V Meteor Cruise 18/1 in the North Atlantic Ocean.

  1. Carbon-related data and preliminary hydrographic measurements were provided to CDIAC by K. M. Johnson and D. W. R. Wallace of BNL. The final hydrographic and chemical measurements and the station information files were provided by the WOCE Hydrographic Program Office after quality evaluation. A FORTRAN 77 retrieval code was written and used to merge and reformat all data files.

  2. To check for obvious outliers, all data were plotted using a PLOTNEST.C program written by Stewart C. Sutherland of 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. 6 and Fig. 7).

  3. To identify noisy data and possible systematic, methodological errors, property-property plots for all parameters were generated (Fig. 8) and carefully examined.

  4. All variables were checked for values that exceeded physical limits, such as sampling depth values exceeding the given bottom depths.

  5. Dates, times, and coordinates were checked for bogus values (i.e., values of MONTH that were <1 or >12; DAY values <1 or >31; YEAR values > or < 1991; TIME values <0000 or >2400; LAT values <49.000 or >65.000; LONG values <- 43.000 or >- 3.000).

  6. Station locations (latitudes and longitudes) and sampling times were examined for consistency with maps and with cruise information supplied by K. M. Johnson and D. W. R. Wallace, BNL.

  7. The designation for missing values, given as - 9.0 in the original files, was changed to - 999.9.

akozyr 7/1/96