NCDC TD3505 Integrated Surface Hourly Data, 1901-continuing

This worldwide collection of surface weather observations is produced at the National Climatic Data Center (NCDC) from NCDC Surface Airway Hourly Observations (TD3280 [https://rda.ucar.edu/datasets/ds470.0/]), U.S.A.F. DATSAV3 Surface Hourly Observations (TD9956 [https://rda.ucar.edu/datasets/ds463.2/]), and NCDC Cooperative Hourly Precipitation (TD3240 [https://rda.ucar.edu/datasets/ds505.0/]). Observations are all in the same ASCII format. Mandatory 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.