Quality control data in GHCN2

In early tests, the program occasionally skipped some of the data in the quality control (QC in GHCN2, flag in GHCN1 parlance) files, even in the simplest read-and-write routines. I was unable to discover the cause of the skips.

Part of the problem may line in a change in formatting of GHCN quality control data. In GHCN1, a flag value is given for every monthly value in the corresponding climate file. In GHCN2, NCDC switched a one-entry-per-line format in which only monthly values with questionable data points are listed. Such a format saves a tremendous amount of space, but is more of a challenge (for me) to write appropriate search codes for.

There were no patterns to the data omissions that I could discern, but I continued to revise the search procedures until I at least minimized the problem.

Given the apparent random nature of the skipping, I cannot be completely sure that successful tests on my part represent a successful correction, therefore I recommend you compare the GHCN2 flag output with the original GHCN2 QC files to see if there are any gaps.

Copyright 1995-2011, David M. Lawrence

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