Establishing Benchmark Daily Station Extremes of Temperature and Precipitation for U.S. Local Climatology Network Stations

NOAA's Regional Climate Centers have developed an integrated, near-real-time database that is synched with the National Climatic Data Center (NCDC) database and accessed using the Applied Climate Information System (ACIS). ACIS is a database infrastructure that has proven ideal for supporting inquiries for climate summaries by National Weather Service field locations using the xmACIS interface. However, one of the great challenges facing the users of xmACIS and other groups (e.g., media and general public users) is the fragmentation of station information over time due to station relocations. A typical first-order location has 3-6 site changes over the course of its full period of record. As a result, obtaining a long series (i.e., one hundred years or more) for computation of extremes is difficult. For the 255 published Local Climatological Data (LCD) sites, a methodology has been employed to create long-term "threaded" data records for the express purpose of computing daily temperature (maximum and minimum) and precipitation extremes. Among other things, the methodology dictates that the record of a currently active station should take precedence over a closed stations record during any periods of overlap. For historic overlaps, the more recent period also takes precedent. The resultant "threaded" data set and derived extremes data tables reflect daily records that typically extend back to 1900 rather than 1948 with many previous, fragmented data sets. Climate data records digitized through NCDC's Climate Database Modernization Program account for much of the extended period of record. The "threaded" data extremes tables will be made publicly available through xmACIS and web pages for climate perspectives applications by climate services and media groups in early 2006, simultaneously assuring a maximized period of record and a consistent basis for reporting daily temperature and precipitation extremes for most cities in the United States.