WMO Codes and Migration to TDCF (www.wmo.int/pages/prog/www/WMOCodes.html) provides the formal definition of the codes and links to the templates and regulations, which are available online (www.wmo.int/pages/prog/www/WMOCodes/WMO306_vI2/TemplateExamples.html). An important feature is that a BUFR radiosonde message should contain all the data from an ascent (or all the data up to 100 hPa for the preliminary report); BUFR was not designed to contain a single part (A, B, C, or D) converted from TEMP. Unfortunately, converting single parts was/is common practice and the cause of most invalid radiosonde BUFR reports. In June 2015 WMO CBS reiterated that converted single parts do not conform to BUFR regulations and also stated that “It is preferable to use the highest resolution information available directly from radiosonde systems when compiling a report in BUFR”. There have been various attempts to merge together TEMP parts A, B, C and D and convert the profile to BUFR, none have been entirely successful. Data converted from Traditional Alphanumeric Codes (TAC) will not include high vertical resolution or the position of each level ("drift" locations) which allows better usage of the profiles in NWP. Various radiosonde manufacturers (Vaisala, MeteoModem, Graw and InterMet, hopefully others over time) provide software to generate high resolution BUFR reports - generally of good quality. In some other cases the National Meteorological Service has taken the lead to generate high resolution BUFR reports directly from raw radiosonde data.
Example of invalid BUFR data converted from TAC: light blue solid lines (black solid lines are from the alphanumeric report, dashed lines from the ECMWF model). The caption "BUFR 1 10 3 284 25 13 10" means that there were four separate BUFR reports with between 1 4 and 28 25 levels.
Example of good high resolution BUFR data: dark blue solid lines (dashed lines from the ECMWF model).
...