The U.S. historical climate network, version 2

Since the original release of the US Historical Climate Network (USHCN), newly available historical data sources and newly developed analysis methods have been implemented. Data rescue efforts provided under the Climate Database Modernization Program (CDMP) have added 279 USHCN-station years of previously unavailable digital data. At the same time, 80 of the original USHCN stations have closed, thereby forcing the development of new composite series. These newly available historical data from non-USHCN stations allow for enhanced quality assurance; estimates of missing values; and the detection of relative change points (non homogeneities). Here, we describe some of these enhancements to the USCHN Version 2 and discuss some differences between the original and new release.