June 9, 2015 USCHN Version 2.5.5 has been released. See Technical Report GHCNM-No15-01 in ftp://ftp.ncdc.noaa.gov/pub/data/ghcn/v3/techreports/ for details on the changes associated with this version update. USHCN Version 2.5.5 homogenized data are associated with the naming convention "52j" to reflect the version of the Pairwise Homogenization Algorithm used. May 28, 2015 USHCN Version 2.5.0 will be replaced by Version 2.5.5 in early June, 2015. Information on this change is available in Technical Report GHCNM-No15-01. Accordingly, the PHA algorithm change will results in a version change from 52i to 52j. July 3, 2014 Note that all estimated values in the USHCN v2.5 dataset are identified using the 'E' flag. As described in the previous versions of the readme.txt file, NCDC's intent was to use a flagging system that distinguishes between estimates for values that were originally missing versus those that were removed as part of the homogenization process. NCDC intends to fix this issue in flag identification in the near future. October 1, 2013 During the shutdown of government operations, USHCN version 2.5 will continue to update automatically (subject to the availability of input data sources), but will not be monitored by the USHCN team. We will also be unable to answer questions submitted to ncdc.ushcn@noaa.gov until after government operations resume. February 14, 2013 An omission in the USHCN Time of Observation bias (TOB) correction process prevented the seasonally varying TOB adjustments from being applied to the USHCN version 2.5 "FLs.52i" temperature data. This ommission began on Oct. 22, 2012. The ommission was rectified on February 12, 2013 when the seasonally varying TOB adjustment resumed in the processing o f the FLs.52i files. Between October 22, 2012 and February 12, 2013, the Pairwise Homogeneization Algorithm (PHA) continued to function and provided an annual mean correction for the time of observation bias in the processing of the "FLs.52i" files. Additional details on may be found at http://www.ncdc.noaa.gov/sotc/national/2013/1/supplemental/page-5 04 October 2012 USHCN v2.5 data are expected to be deployed to this ftp directory during the week of October 8, 2012