7.3 WMO Index Numbers . A station index number in the symbolic form IIiii is included in the reports of meteorological observations made at fixed land meteorological stations or aboard ships using land code forms. The two-digit block number defines the area in which the reporting station is located. Assignment of International Station Index Numbers . These numerical designations facilitate identifying, switching, and processing the bulletins and data that the individual stations provide.
Quality control is imperative to ensure the accurate transmission of station numbers.
An erroneous index number can cause either a loss of the report or assignment of the data to the wrong location if the erroneous number happens to be that of another station. If a station moves, even a short distance, a new index number may need to be assigned. Stations shall be responsible for obtaining a proper index number. 7.4 Transmitting Rawinsonde Reports . The complete observation shall be transmitted not later than 30 minutes after termination of the ascent.