Byrd 18Z pressure 1980 - - 813.1 818.6 817.4 803.0 817.3 811.5 811.2 801.0 816.0 816.6 1981 - 816.8 818.0 813.9 808.1 802.2 805.6 806.1 806.1 805.9 804.4 809.8 1982 821.4 813.4 804.0 798.8 804.7 804.2 807.9 801.5 796.8 801.8 812.6 824.3 1983 820.7 816.6 812.0 808.0 813.0 804.7 799.0 795.2 802.6 794.5 803.2 812.8 1984 821.7 816.5 809.0 808.5 810.2 810.1 793.5 799.4 798.4 807.7 807.0 821.5 1985 820.2 813.3 811.1 808.6 811.2 806.2 790.2 799.5 796.9 800.1 802.4 810.1 1986 816.4 819.8 814.1 807.1 819.4 812.9 801.2 799.2 793.8 798.2 805.8 812.3 1987 821.8 815.8 804.1 809.9 810.1 811.2 815.3 801.8 808.7 801.0 803.4 816.5 1988 817.6 811.8 - - - - - - - - - - 1989 - - - - - - - - - - - - 1990 - 810.2 809.9 815.8 819.1 802.6 811.8 799.0 794.0 - - - 1991 - 818.1 805.1 808.0 813.3 811.4 811.3 799.8 804.2 804.4 810.6 825.3 1992 818.5 821.5 816.8 808.8 819.1 - - - - - - - 1993 - 810.0 810.3 806.0 - - 802.5 800.5 - 801.0 808.1 812.6 1994 - 809.7 804.5 812.1 810.1 818.7 811.7 793.8 806.2 806.1 815.0 815.6 1995 812.9 811.7 814.0 805.8 803.6 818.4 819.9 808.1 801.6 803.4 806.6 809.8 1996 817.4 816.0 807.5 - - - - - - - - - 1997 - 818.8 806.4 807.1 799.8 814.5 803.2 798.2 805.8 809.1 819.5 823.2 1998 815.5 813.6 808.6 798.7 811.6 807.0 800.8 799.8 807.4 804.7 801.0 812.6 1999 814.7 813.3 808.8 803.2 798.8 - - - - - - 805.6 2000 - - - - - 810.6 805.8 809.2 - - - - 2001 - - - - - - - - - - - - 2002 814.3 806.6 818.8 - - - - - - - - 811.1 2003 - - - - - - - - - - - - 2004 - - - - - - - - - - - - 2005 - - - - - - - - - - - - 2006 - - - - - - - - - - - - 2007 - - - 814.3 809.1 810.9 820.5 803.9 - - 814.2 807.3 2008 815.3 811.7 814.1 809.9 806.9 - - - - 803.6 - - 2009 - - - - - - - - - - - -