Did You Know?

National Data Flow

NOAA's National Centers for Environmental Information (NCEI) is the world's largest active archive of weather data. Each month, observers that are part of the National Weather Service Cooperative Observer Program (COOP) send their land-based meteorological surface observations of temperature and precipitation to NCEI to be added to the U.S. data archives. The COOP network is the country's oldest surface weather network and consists of more than 11,000 observers. At the end of each month, the data are transmitted to NCEI via telephone, computer, or mail.

Typically by the 3rd day of the following month, NCEI has received enough data to run processes which are used to calculate divisional averages within each of the 48 contiguous states. These climate divisions represent areas with similar temperature and precipitation characteristics (see Guttman and Quayle, 1996 for additional details). State values are then derived from the area-weighted divisional values. Regions are derived from the statewide values in the same manner. These results are then used in numerous climate applications and publications, such as the monthly U.S. State of the Climate Report.

The U.S. operational suite of products transitioned from the traditional divisional dataset to the Global Historical Climatological Network (GHCN) dataset in the summer of 2011. The GHCN dataset is the world's largest collection of daily climatological data. The GHCN utilizes many of the same surface stations as the current divisional dataset, and the data are delivered to NCEI in the same fashion. Further details on the transition and how it will affect the customer will be made available in the near future.