This worldwide collection of surface weather observations is produced at the National Climatic Data Center (NCDC) from NCDC Surface Airway Hourly Observations (TD3280), U.S.A.F. DATSAV3 Surface Hourly Observations (TD9956), and NCDC Cooperative Hourly Precipitation (TD3240). Observations are all in the same ASCII format.

Manadatory data includes pressure, temperature, dew-point, visibility, sky condition, and wind observation, but there may also be additional data, data remarks, or data element quality sections.

The earliest data is for 1901. The earliest years have the least volume of data, a few hundred megabytes; the volume in the 1950s-early 1960s increased by a factor of 10-20; 1965-1972 shows a decrease because of a loss of data; beginning in 1973 with about 5 gigabytes of data, volume has gradually increased to about 20 gigabytes per year. There are now about 10,000 active stations. For frequent updates to recent data and occasional updates to the historical data, access the data directly from NCDC.

Similar data sets prepared by the National Centers for Environmental Prediction (NCEP) are ds464.0 (beginning February 1975), and ds461.0 (beginning April 2000).

Requests for this data from non-NCAR users will be forwarded to NCDC.