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 Section P6 in the South Pacific Ocean.

    
 1.    The final carbon-related data were provided to CDIAC by D. W. R. Wallace
       and K. M. Johnson of Brookhaven National Laboratory.  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.    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 (Figs. 8-13 in online doc.). 
       Several outliers were identified and marked with the quality flags of "3"
       questionalbe measurement) or "4" (bad measurement) (see File Descriptions
       in Part 2 of this documentation).
    
 3.    To identify "noisy" data and possible systematic, methodological errors,
       property-property plots for all parameters were generated (Fig. 14 in online 
       documentation), carefully examined, and compared with plots from previous
       expeditions in the Pacific Ocean.
    
 4.    All variables were checked for values exceeding physical limits, such as
       sampling depth values that are greater than the given bottom depths.
    
 5.    Dates, times, and coordinates were checked for bogus values (e.g., 
       values of MONTH <1 or >12; DAY <1 or >31; YEAR < or >1992;  
       TIME <0000 or >2400; LATITUDE <25.000 or >32.000; LONGITUDE < 150.000
       or >80.000. 
    
 6.    Station locations (latitudes and longitudes) and sampling times were
       examined for consistency with maps and cruise information supplied by 
       D. W. R. Wallace and K. M. Johnson of BNL.
    
 7.    The designation for missing values, given as  9.0 in the original files,
       was changed to 999.9 for consistency with other oceanographic data sets.
    

 
tbeaty 04/18/2002