U.S. controlled station time series of upper air observations (soundings) comprise the data in this set. From the National Climatic Data Center (NCDC), DSS obtains annual updates of the DSI-6301 UPPER AIR DIGITAL FILES, which are then quality checked, reformatted, hydrostatically checked, and merged into existing station time series.

Primarily, stations are located in the contiguous U.S., Alaska, the Caribbean, Hawaii and other Pacific Islands, plus Keflavik, Ascension Island, Diego Garcia, and the South Pole. There are currently about 110 stations received.

Mandatory, standard, and significant levels may include pressure, height, temperature, moisture, wind direction and speed. Earliest data is for 1945, but periods of record vary widely among the stations.