GLOBAL HISTORICAL CLIMATOLOGY NETWORK (GHCN) QUALITY
CONTROL OF MONTHLY TEMPERATURE DATA
ABSTRACT
All geophysical data bases need some form of quality assurance. Otherwise, erroneous data points may produce faulty
analyses. However, simplistic quality control procedures have been known to contribute to erroneous conclusions by
removing valid data points that were more extreme than the data set compilers expected. In producing version 2 of
the global historical climatology network’s (GHCN’s) temperature data sets, a variety of quality control tests were
evaluated and a specialized suite of procedures was developed. Quality control traditionally relies primarily on checks
for outliers from both a time series and spatial perspective, the latter accomplished by comparisons with neighbouring
stations. This traditional approach was used, and it was determined that there are many data problems that require
additional tests to detect. In this paper a suite of quality control tests are justified and documented and applied to
this global temperature data base, emphasizing the logic and limitations of each test. © 1998 Royal Meteorological
Society.
KEY WORDS: Global historical climatology network (GHCN); quality control; temperature, monthly; homogeneity tests; outliers