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Synoptic Surface Data Conversion

The synoptic surface observation data conversion program called smcvt decodes all station information that is encoded in the synoptic (SYNOP), synoptic ship (SYNOP SHIP), drifting buoy (DRIBU) or CMAN (SYNOP) data format. Stationary buoys and ship data report under the SYNOP format. The synoptic surface data is reported worldwide every 6 hours. This is the global standard for reporting surface data and thus better global coverage can be obtained by using synoptic data.  The U.S. on the other hand does not use synoptic format and thus these reports should be augmented with U.S METAR reports.  Surface reports contain the following encoded information:

  • ID -- station identifier
  • TEMP -- temperature
  • DEWPT -- dewpoint
  • SLP -- sea level pressure
  • CEIL -- cloud ceiling
  • COVER -- cloud coverage,
  • VIS -- visibility
  • WIND -- wind direction and speed
  • PTEND -- pressure tendency for a 3 hour period
  • PREC6 -- precipitation amounts for 6 hours
  • WX -- present and past weather
  • CTYPE -- cloud type information for low, medium and high clouds
  • EXTT - extreme temperatures
  • PREC -- 1,3,6,12 or 24 hour precipitation
  • SNOW -- snow cover in inches (reported at 12 GMT)
  • SST -- sea surface temperature
  • WAVE -- sea wave height and period

The conversion program tries to match the coded data to a synoptic coding standard. Corrupted reports will cause the decoding process to terminate for that report. Regional codes will not be decoded. The resulting information is then saved in either ASCII WXP format or netCDF format just as with sacvt. The output file may save the ID either as the WMO number (as broadcasted) or as a station ICAO ID (3 or 4 letter). If the station does not have an ICAO ID, one will be derived from the WMO number using the 2 letter country prefix and the last 3 numbers of the WMO number.  Country prefixes are listed in the Global Station Information Appendix.

For further information about WXP, email technical-support@weather.unisys.com
Last updated by Dan Vietor on June 24, 1998