Access to the Global Upper Air Sounding Archive at NCAR

Over the past 40 years, the Data Support Section (DSS) of the National Center for Atmospheric Research (NCAR) has collected over 70 million upper air soundings from more than 30 sources. This archive includes wind only soundings (pibals) for the period 1920-2000 and radiosondes (raobs) for the period 1947-2000. The different sources for the data include the Global Telecommunication System (GTS) feed from the National Center for Environmental Predictions, several datasets from the United States Air Force, individual countries, field projects and permanent and moving ships. In total, these soundings were used as a primary component for global atmospheric reanalyses at NCAR, ECMWF and others. During data preparation for the reanalyses many tests for systematic errors were performed, including verification and update of station position and elevation, hydrostatic data checks, and horizontal track checks in the case of moving platforms. The data are provided in a form where each data source is identified and the original data are preserved. This approach contrasts with the Integrated Global Sounding Archive, in which data merging and duplicate sounding elimination as prescribed by NCDC are the primary features.

Software and an easy to use interface now make these reference observations conveniently available to users. The web interface will allow for the selection of single or multiple stations and will also provide the ability to select all stations within a user supplied geographic region. As noted above, access to all soundings will be provided, however, options for eliminating duplicates will also be available.

The data have been archived in 2 different formats: NCAR's Time Series Raob (TSR) and NCEP's ON29 format. Data from all sources have been converted to the TSR format, except for the NCEP GTS feed for 1973 – 2000, which is in the ON29 format. The result is that all data prior to 1973 are in the TSR format, but for 1973 and later the data can be in either format. Users will have the option to obtain the data in the TSR or ON29 formats, when available, or choose to have all soundings output in a simple common ASCII format. In either case, the output can be sorted synoptically or in time series by station.