international synoptic surface observation code
From Glossary of Meteorology
A code to report surface observations.
References: 1) International synoptic codes FM 12-XI SYNOP Report of surface observations from a fixed land station; 2) FM 13-XI SHIP Report of surface observations from a mobile land station; and 3) FM 14-XI SYNOP MOBIL Report of surface observations from a mobile land station.
World Meteorological Organization 1995. Manual on Codes, VI.1 Part A. WMO-No. 306, . p. 1.9-A-1.