The TAC to BUFR Migration—Current Status of BUFR Surface and Upper-Air Observations

Although the WMO-mandated TAC-to-BUFR migration was to have been completed by November 2014, it is still far from finished. Even so, many countries especially in Europe are now exclusively using BUFR for surface and upper-air data and have ceased distribution of TAC (Traditional Alphanumeric Codes, such as SYNOP and TEMP). The U.S. has been providing native BUFR radiosonde reports from most NWS stations for over a year now, joining most of Europe, Australia, New Zealand, Canada, South Korea, Chile, South Africa and a few other countries. (“Native” in this context refers to data originating in the radiosonde ground station including drift times and horizontal displacements, and typically at 1- to 2-second resolution.) Japan started disseminating native BUFR in early July 2018, and Canada is in the process of fielding Graw radiosonde systems and switching from low-resolution to high-resolution native BUFR. In addition, the U.S. is switching to Vaisala Autosonde systems at Alaskan stations. Switching to BUFR is in some respects easier for surface data, although many countries including the U.S. are doing this by reformatting TAC. Reformatting TAC to BUFR, whether for radiosonde or surface observations, leads to the possibility of errors in station metadata (i.e. elevation, latitude, longitude) since these values must be supplied from a station list for the required translation to BUFR. This presentation will examine the current availability of BUFR and TAC surface and upper-air observations, including a comparison with previous years. Current errors in BUFR data and metadata will also be addressed. Observation impacts (FSOI) from NAVGEM, the U.S. Navy’s operational global numerical weather prediction model, will be presented for both TAC and BUFR observations. Finally, WMO’s upcoming change from 5-digit block-station numbers to four-part WIGOS identifiers will be described.