U.S. Climate Extremes Index (CEI): Data Used

NCEI replaced input data for the CEI mean monthly maximum and minimum temperature extremes on Thursday, October 6, 2016, coincident with the release of the September 2016 monthly monitoring report. For more information, please read below.

Data Used

The U.S. CEI is based on an aggregate set of conventional climate extreme indicators which, at the present time, include the following types of data:

  1. monthly maximum and minimum temperature
  2. daily precipitation
  3. monthly Palmer Drought Severity Index (PDSI)
  4. landfalling tropical storm and hurricane wind velocity

* experimental (not used with the Regional CEI)

Each indicator has been selected based on its reliability, length of record, availability, and its relevance to changes in climate extremes.

In October 2016, NCEI's nClimGrid (Vose et al., 2014) dataset replaced USHCN version 2.5 as the input dataset for CEI's mean maximum and minimum temperature extremes. The nClimGrid dataset improves spatial resolution (5km versus 1° grids with the USHCN data) and is serially complete throughout the CEI period of record (1910-present). The nClimGrid dataset also has complete spatial coverage across the contiguous U.S.

Beginning in March 2012, daily precipitation data were extracted from the GHCN-Daily dataset. Prior to this, daily precipitation stations were extracted from the USHCN daily database and supplemented by Summary of the Day (TD3200) and pre-1948 (TD3206) daily precipitation stations. A mimimal number of missing days within each year and period of record were also a requirement for precipitation stations to be included in the CEI calculations.

The National Centers for Environmental Information (NCEI) climate division precipitation and temperature databases are used to calculate the PDSI (Karl 1986). The PDSI categorizes moisture conditions in increasing order of intensity as near normal, mild to moderate, severe, or extreme for droughts and wet periods, which fit nicely into the CEI framework.

Tropical storm and hurricane wind data, extracted from the National Hurricane Center's North Atlantic Hurricane Database (HURDAT), are the newest addition to the CEI and are included in the index when such a storm crossed over contiguous U.S. land. Multiple landfalls from tropical systems are considered valid and are used as many times as they hit land.