U.S. Climate Reference Network Extreme Events Index

The U.S. Climate Reference Network (USCRN) is a high quality observation system designed to accurately measure climate change in the United States. Aspirated air temperature, well-shielded precipitation, and multi-level soil moisture are all measured in triplicate at each station, insuring that any operational errors can be detected and excluded by intercomparing the individual observations. USCRN temperature observations have been fully representative of the conterminous U.S. conditions on a monthly basis since 2005, and have been used to produce a National Temperature Index product that verifies the U.S. monthly averages determined by the full set of thousands of observation stations of varying quality (see https://www.ncei.noaa.gov/access/monitoring/national-temperature-index/).

In recent years, official 1991-2020 normals for temperature and precipitation have been estimated for USCRN stations, allowing the calculation of monthly station standardized anomalies. For each station, time series of monthly standardized anomalies of maximum and minimum temperature and precipitation provide the basis for a variety of extremes indices based on the fraction of stations in any given month exceeding a threshold. Several thresholds were examined, including 1 and 2 standard deviations. The fraction of stations above normal and below normal temperatures and precipitation will be examined individually in this presentation, along with a combined USCRN Extreme Events Index equally weighted between temperature and precipitation extreme fractions.