GTS Data for GCOS Upper-Air Network (GUAN) Stations
(Readme file last updated by Imke Durre on December 12, 2001)

Period of record: October 2001 to present

Update frequency: daily

Quality control: removal of duplicate soundings and levels;
removal of syntax errors; gross limit checks; only levels with 
(1) a valid pressure and/or geopotential height value and 
(2) valid temperature and/or wind observations are retained.

Files: one file per month, with the current month's file ending 
on the most recent date loaded

Data format: TD63 format with a carriage return after each header 
and data record and no limit on the number of levels per sounding record

Notes:
1. The data for 10-15 GUAN stations do not appear to be transmitted 
   to NCDC via the GTS. 
2. A month's data file may contain some late-coming soundings taken 
   at the end of the previous month.
3. Within each sounding, thermodynamic levels are sorted by descending 
   pressure. Wind-only levels are grouped together at the end of the 
   sounding. Wind levels identified 
   by geopotential height only are sorted by ascending height; 
   wind levels identified by pressure only are sorted by descending 
   pressure.