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ECMWF 1 Com Intro training course - 2004 BUFR decoding BUFR decoding Dominique Lucas – Milan Dragosavac User Support – Meteorological Application.

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Presentation on theme: "ECMWF 1 Com Intro training course - 2004 BUFR decoding BUFR decoding Dominique Lucas – Milan Dragosavac User Support – Meteorological Application."— Presentation transcript:

1 ECMWF 1 Com Intro training course BUFR decoding BUFR decoding Dominique Lucas – Milan Dragosavac User Support – Meteorological Application

2 ECMWF 2 Com Intro training course BUFR decoding Content BUFR data format BUFR software BUFR tool Practical example

3 ECMWF 3 Com Intro training course BUFR decoding What is BUFR Binary representation of meteorological data or Binary Universal Form for data Representation Continuous bit stream made of sequence of octets. Table driven code Self descriptive code Machine independent Compression available for improved transmission speed

4 ECMWF 4 Com Intro training course BUFR decoding BUFR FORMAT Indicator section Identification section Optional section Data description section Data section End section All sections are padded with 0s if needed to occupy even number of octets.

5 ECMWF 5 Com Intro training course BUFR decoding Section 0 - Indication section

6 ECMWF 6 Com Intro training course BUFR decoding Section 1 - Identification section

7 ECMWF 7 Com Intro training course BUFR decoding Section 1 - Identification section

8 ECMWF 8 Com Intro training course BUFR decoding Section 1 - Identification section ADP: Automated Data Processing

9 ECMWF 9 Com Intro training course BUFR decoding Section 2 - Optional section

10 ECMWF 10 Com Intro training course BUFR decoding Section 3 - Data description section

11 ECMWF 11 Com Intro training course BUFR decoding Section 3 - Data descriptors F = 0 Element Descriptor – Bufr table B F = 1 Replication descriptor X = number of descriptors to repeat Y = number of times the descriptors are repeated F = 2 Operator Descriptor – Bufr table C F = 3 Sequence Descriptor – Bufr table D

12 ECMWF 12 Com Intro training course BUFR decoding Section 4 - Data section

13 ECMWF 13 Com Intro training course BUFR decoding Section 5 - End section

14 ECMWF 14 Com Intro training course BUFR decoding BUFR Tables Table A - Data category Table B - Classification of elements Table C - Data descriptor operators Table D - List of common sequences

15 ECMWF 15 Com Intro training course BUFR decoding Table A - Data category Used in the Section 1 (element 9) of the BUFR message Example: Code figureMeaning 0Surface data - land 1Surface data – sea 2Vertical soundings (not satellite) … 31Oceanographic data

16 ECMWF 16 Com Intro training course BUFR decoding Table B - Classification of elements Element Name Unit Scale Reference #bits Latitude (high accuracy) Degree Geopotential m**2/s** Satellite instruments Code table Vertical sounding signifi Flag Table Aircraft flight number CCITTIA (obs. * 10**scale – Reference) is encoded into #bits bits For coded or flagged values, the element descriptor indicates the number of the table discribing the codes/flags. 0 - Table B entry 05 - Location (horizontal 1) class 01 - Identification 08 - Significance qualifiers

17 ECMWF 17 Com Intro training course BUFR decoding Table C - Data Descriptor operators 201yyy - Change data width 202yyy - Change scale 203yyy - Change reference value Quality information

18 ECMWF 18 Com Intro training course BUFR decoding Table D - List of common sequence Table D can contain sequences of table B entries, Table D entries and Operators. It is not needed but saves a lot of space WMO block and station Radiosonde type Radiosonde computational method Date Time Lat/Long and station height

19 ECMWF 19 Com Intro training course BUFR decoding Bufr software PBIO routines PBOPEN- open bufr file for read/write PBBUFR- read bufr message PBWRITE- write bufr message

20 ECMWF 20 Com Intro training course BUFR decoding BUFR decoding CALL BUFREX ( kbufl, kbuff, ksup, ksec0, ksec1, ksec2, ksec3, ksec4, kelem, cnames, cunits, kvals, values, cvals, kerr ) Input arguments kbufl - length of bufr message in words kbuff - array containing bufr message kelem - expected number of expanded elements kvals - size of values array

21 ECMWF 21 Com Intro training course BUFR decoding BUFR decoding Output arguments ksup- array containing supplementary information ksec[0-4] - array containing section [0-4] information cnames- character array containing element names cunits- character array containing element units values- real array containing element values cvals - character array containing char. elem. Values kerr- return code

22 ECMWF 22 Com Intro training course BUFR decoding BUFR decoding To access character strings from cvals array index = values(1)/1000 string = cvals(index) value(1) = index * length To access i-th element in multi subset message from values array index = i +(nsub-1) * kelem

23 ECMWF 23 Com Intro training course BUFR decoding BUFR Tables BUFR Edition 3 naming convention Bwwwxxxyyzz, Cwwwxxxyyzz, Dwwwxxxyyzz B- Bufr table B C- Bufr table C code and flag tables D- Bufr table D www- Originating subcentre xxx- Originating centre yy- Version number of master table used zz- Version number of local table used

24 ECMWF 24 Com Intro training course BUFR decoding Where to find more about BUFR WMO manual on Codes, Volume I, InternationalCodes, Part B-Binary Codes, WMO No.306, FM-94-IX Ext BUFR BUFR User Guide and Reference Manual, Ecmwf Guide to WMO Table Driven Code Forms

25 ECMWF 25 Com Intro training course BUFR decoding BUFR tool BUFR profiler available from /home/ma/emos/bin/sgimips/xbdc

26 ECMWF 26 Com Intro training course BUFR decoding Practical examples On ecgate, take a copy of ~trx/bufr_decode/Retrieve_decode_bufr.cmd Run (interactively or in batch mode) Retrieve_decode_bufr.cmd to decode one synop observation. Use ~emos/bin/rs6000/xbdc on ecgate to display the content of the bufr message in ~trx/bufr_decode/obs Try to adapt Retrieve_decode_bufr.cmd to write part of the observation data out to a file. An example job is available in ~trx/bufr_decode/ Retrieve_extract_bufr.cmd


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