Table 1: Data Sources for IGRA
  Data Source Period of Record Area of Coverage Number of Stations Percent of IGRA Soundings
Core NCDC Historical GTS 1963-1970 Global 820 7.94
NCAR/NCEP GTS 1970-1972 Global 848 3.01
NCEP GTS 1973-1999 Global 1517 64.06
NCDC Real-Time GTS 2000-present Global 1093 7.13
Other Large Scale Russian GTS 1998-2001 Global 923 1.59
U.S. Air Force 1946-1973 Global 292 4.49
Australian GTS 1990-1993 Southern Hemisphere 170 0.15
Country-specific U.S. 1946-2001 U.S. & U.S. military 150 9.81
Australian 1938-1989 Australia & territories 17 1.63
Argentine 1958-1991 Argentina 8 0.18
South Korean 1984-1992 South Korea 4 0.01