A comparison of the original United States Historical Climatology Network (USHCN) and USHCN v2

The U.S. Historical Climatology Network began in 1983 to provide long-term homogeneous monthly temperature and precipitation series across the United States. NOAA's NCDC has produced a 2005 release (Version 2) with improved change-point detection and employing the U.S. Cooperative Network and the early 20th century data from the Climatic Data Modernization Project.

Adjusted maximum and minimum monthly temperature series from Version 2 are compared to series processed using the original USHCN artificial change point adjustment algorithms. The frequency distribution of change-point adjustments is examined in order to evaluate the impact of incorporating undocumented change point detection algorithms in the Version 2 release. Regional and national trends, calculated using the new and original series, are discussed.