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Modifications to pairwise homogeneity adjustment software to improve run-time efficiency
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  • Description:
    The software used to perform operational updates and re processing of GHCN - M version 3 was modified to correct software coding errors and to improve its run-time efficiency. In particular, errors in the Pairwise Homogenization Algorithm (PHA) were identified during the course of a project led by Mr. Daniel Roth enberg in July 2011 that was undertaken as part of Google's "Summer of Code" and supervised by the Climate Code Foundation (with collaboration by NOAA/NCDC). The errors and steps taken to correct each error are described in this technical report. In addit ion, changes were made to improve debugging and data processing efficiency. A comparison of U.S. and global analyses performed using the PHA software before and after the corrections and modifications are included. With the software corrections the sensiti vity of the PHA improved, resulting in an approximate two-fold increase in the frequency of bias adjustments applied globally. The impact on annual means resulted in a change in century-scale global land surface air temperature trends of approximately 0.01°C/decade. The software modifications are incorporated into a new release of GHCN-M, version 3.2.0.
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