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| Year | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1950 | 1009.6 | 1012.5 | 1010.7 | 1017.2 | 1010.6 | 1009.1 | 1007.3 | 1007.6 | 1011.8 | 1015.6 | 1015.5 | 1009.3 | 1011.4 |
| 1951 | 1013.0 | 1015.6 | 1011.0 | 1012.6 | 1007.2 | 1006.9 | 1009.4 | 1007.7 | 1010.2 | 1013.8 | 1014.1 | 1011.8 | 1011.1 |
| 1952 | 1011.4 | 1013.1 | 1013.8 | 1012.4 | 1009.5 | 1007.0 | 1008.5 | 1010.0 | 1010.2 | 1014.2 | 1017.4 | 1015.6 | 1011.9 |
| 1953 | 1013.4 | 1015.8 | 1012.8 | 1012.1 | 1013.3 | 1009.9 | 1009.0 | 1008.9 | 1011.9 | 1015.3 | 1013.9 | 1016.8 | 1012.8 |
| 1954 | 1014.8 | 1014.2 | 1015.2 | 1012.5 | 1007.9 | 1013.6 | 1012.0 | 1010.8 | 1010.9 | 1017.5 | 1015.8 | 1014.0 | 1013.3 |
| 1955 | 1013.1 | 1007.8 | 1015.0 | 1010.7 | 1013.0 | 1006.9 | 1005.7 | 1010.0 | 1013.5 | 1014.0 | 1014.0 | 1007.5 | 1010.9 |
| 1956 | 1007.0 | 1009.2 | 1016.5 | 1007.1 | 1006.8 | 1009.9 | 1010.5 | 1009.2 | 1012.3 | 1016.6 | 1014.8 | 1011.1 | 1010.9 |
| 1957 | 1012.4 | 1014.3 | 1010.6 | 1009.3 | 1010.1 | 1008.9 | 1007.7 | 1009.6 | 1010.8 | 1011.4 | 1014.3 | 1012.1 | 1011.0 |
| 1958 | 1011.0 | 1015.4 | 1008.1 | 1010.4 | 1008.7 | 1008.1 | 1006.7 | 1010.8 | 1011.5 | 1017.6 | 1017.2 | 1013.2 | 1011.6 |
| 1959 | 1010.3 | 1017.1 | 1017.3 | 1008.2 | 1009.4 | 1009.5 | 1005.9 | 1009.4 | 1010.9 | 1014.7 | 1015.7 | 1013.3 | 1011.8 |
| 1960 | 1011.2 | 1010.5 | 1013.1 | 1011.3 | 1010.3 | 1009.4 | 1008.0 | 1009.3 | 1010.6 | 1019.3 | 1016.3 | 1009.6 | 1011.6 |
| 1961 | 1012.4 | 1008.6 | 1014.2 | 1008.2 | 1007.2 | 1007.0 | 1005.3 | 1009.7 | 1010.7 | 1017.5 | 1015.9 | 1012.2 | 1010.7 |
| 1962 | 1008.3 | 1011.6 | 1007.1 | 1012.4 | 1008.2 | 1007.3 | 1009.3 | 1009.6 | 1011.1 | 1015.2 | 1016.4 | 1011.5 | 1010.7 |
| 1963 | 1001.7 | 1013.8 | 1014.2 | 1015.4 | 1007.6 | 1010.7 | 1008.8 | 1009.3 | 1008.4 | 1017.3 | 1012.6 | 1011.3 | 1010.9 |
| 1964 | 1016.5 | 1020.4 | 1015.3 | 1018.2 | 1013.5 | 1008.1 | 1007.1 | 1009.8 | 1012.0 | 1016.5 | 1013.5 | 1013.6 | 1013.7 |
| 1965 | 1012.1 | 1007.4 | 1010.4 | 1009.0 | 1008.4 | 1007.2 | 1006.8 | 1008.8 | 1008.8 | 1014.9 | 1011.3 | 1008.7 | 1009.5 |
| 1966 | 1007.0 | 1009.9 | 1006.4 | 1013.0 | 1010.3 | 1012.2 | 1006.9 | 1009.1 | 1010.0 | 1014.8 | 1010.2 | 1011.2 | 1010.1 |
| 1967 | 1009.3 | 1013.6 | 1010.6 | 1014.8 | 1011.1 | 1006.3 | 1007.0 | 1005.8 | 1014.7 | 1013.2 | 1016.0 | 1011.9 | 1011.2 |
| 1968 | 1005.1 | 1014.2 | 1008.4 | 1017.5 | 1012.9 | 1011.0 | 1006.4 | 1008.4 | 1015.0 | 1015.1 | 1015.1 | 1012.2 | 1011.8 |
| 1969 | 1009.1 | 1013.2 | 1011.1 | 1011.7 | 1004.9 | 1005.0 | 1008.2 | 1008.1 | 1009.6 | 1012.8 | 1013.2 | 1009.5 | 1009.7 |
| 1970 | 1011.9 | 1009.3 | 1008.2 | 1013.9 | 1009.2 | 1009.1 | 1006.9 | 1010.1 | 1009.8 | 1013.8 | 1011.2 | 1008.4 | 1010.2 |
| 1971 | 1013.5 | 1015.2 | 1008.6 | 1010.1 | 1009.1 | 1006.7 | 1004.8 | 1009.4 | 1012.4 | 1012.3 | 1012.7 | 1009.4 | 1010.4 |
| 1972 | 1018.5 | 1011.7 | 1013.1 | 1013.6 | 1005.8 | 1005.6 | 1006.7 | 1005.6 | 1011.6 | 1011.3 | 1011.4 | 1010.8 | 1010.5 |
| 1973 | 1016.0 | 1009.1 | 1010.9 | 1008.3 | 1008.3 | 1010.3 | 1008.6 | 1008.5 | 1011.7 | 1013.9 | 1006.6 | 1003.1 | 1009.6 |
| 1974 | 1009.4 | 1011.9 | 1013.5 | 1007.4 | 1009.9 | 1008.7 | 1009.6 | 1007.0 | 1010.7 | 1010.3 | 1011.3 | 1014.5 | 1010.4 |
| 1975 | 1008.1 | 1011.7 | 1012.1 | 1011.8 | 1010.8 | 1008.7 | 1006.7 | 1007.7 | 1010.8 | 1015.1 | 1018.5 | 1013.3 | 1011.3 |
| 1976 | 1005.1 | 1013.7 | 1011.3 | 1011.5 | 1006.9 | 1009.3 | 1008.0 | 1008.0 | 1013.2 | 1009.7 | 1011.5 | 1009.9 | 1009.8 |
| 1977 | 1012.4 | 1010.8 | 1013.9 | 1008.3 | 1009.4 | 1008.7 | 1006.4 | 1007.3 | 1010.4 | 1016.2 | 1016.4 | 1012.9 | 1011.1 |
| 1978 | 1007.6 | 1011.4 | 1009.2 | 1006.9 | 1008.8 | 1006.5 | 1006.9 | 1005.9 | 1011.0 | 1014.5 | 1014.8 | 1014.1 | 1009.8 |
| 1979 | 1011.4 | 1009.2 | 1011.3 | 1012.6 | 1008.9 | 1008.1 | 1007.1 | 1005.6 | 1012.3 | 1012.0 | 1015.5 | 1014.5 | 1010.7 |
| 1980 | 1008.7 | 1009.6 | 1010.0 | 1013.5 | 1007.4 | 1007.8 | 1008.6 | 1013.4 | 1010.5 | 1011.7 | 1011.3 | 1006.5 | 1009.9 |
| 1981 | 1008.9 | 1011.4 | 1012.7 | 1008.0 | 1008.7 | 1010.0 | 1008.2 | 1003.9 | 1009.8 | 1008.6 | 1011.1 | 1010.8 | 1009.3 |
| 1982 | 1010.8 | 1013.2 | 1011.3 | 1013.3 | 1007.5 | 1006.4 | 1009.4 | 1009.7 | 1010.7 | 1013.1 | 1012.9 | 1010.1 | 1010.7 |
| 1983 | 1010.8 | 1012.4 | 1015.0 | 1008.7 | 1008.1 | 1011.4 | 1007.2 | 1009.2 | 1013.2 | 1009.4 | 1010.9 | 1008.9 | 1010.4 |
| 1984 | 1010.3 | 1010.4 | 1011.6 | 1018.3 | 1013.3 | 1008.4 | 1006.8 | 1008.7 | 1010.1 | 1010.8 | 1013.0 | 1011.6 | 1011.1 |
| 1985 | 1012.8 | 1009.6 | 1016.8 | 1013.0 | 1009.6 | 1010.5 | 1005.9 | 1009.3 | 1012.6 | 1012.2 | 1008.8 | 1010.7 | 1011.0 |
| 1986 | 1008.8 | 1011.6 | 1012.9 | 1009.5 | 1005.8 | 1009.6 | 1009.5 | 1008.0 | 1009.8 | 1014.0 | 1011.8 | 1011.9 | 1010.3 |
| 1987 | 1010.4 | 1009.3 | 1008.4 | 1009.4 | 1008.5 | 1008.8 | 1004.8 | 1009.2 | 1013.5 | 1012.5 | 1013.8 | 1012.5 | 1010.1 |
| 1988 | 1007.7 | 1011.3 | 1012.6 | 1012.4 | 1009.4 | 1007.7 | 1011.4 | 1009.6 | 1013.9 | 1008.5 | 1008.4 | 1008.3 | 1010.1 |
| 1989 | 1016.0 | 1013.8 | 1012.6 | 1009.6 | 1008.0 | 1011.8 | 1011.2 | 1007.6 | 1009.8 | 1012.6 | 1015.6 | 1011.3 | 1011.7 |
| 1990 | 1013.9 | 1021.6 | 1012.9 | 1009.4 | 1009.8 | 1007.8 | 1007.8 | 1006.5 | 1014.0 | 1014.7 | 1013.5 | 1009.4 | 1011.8 |
| 1991 | 1010.0 | 1010.8 | 1013.3 | 1011.6 | 1008.1 | 1005.8 | 1006.4 | 1008.9 | 1011.3 | 1011.0 | 1013.4 | 1014.7 | 1010.4 |
| 1992 | 1012.8 | 1007.7 | 1016.8 | 1008.0 | 1008.2 | 1010.1 | 1004.7 | 1011.5 | 1010.5 | 1014.9 | 1014.0 | 1011.6 | 1010.9 |
| 1993 | 1013.8 | 1008.9 | 1011.5 | 1007.6 | 1009.5 | 1008.2 | 1011.3 | 1008.0 | 1012.0 | 1011.0 | 1015.6 | 1010.6 | 1010.7 |
| 1994 | 1011.2 | 1004.0 | 1011.4 | 1008.3 | 1004.7 | 1008.9 | 1005.8 | 1009.7 | 1010.8 | 1013.5 | 1017.1 | 1012.2 | 1009.8 |
| 1995 | 1008.3 | 1014.3 | 1014.4 | 1008.2 | 1009.2 | 1010.0 | 1005.4 | 1008.2 | 1007.7 | 1013.1 | 1002.7 | 1009.6 | 1009.3 |
| 1996 | 1006.2 | 1010.5 | 1009.5 | 1009.0 | 1011.1 | 1007.9 | 1008.5 | 1010.3 | 1011.4 | 1012.8 | 1011.1 | 1011.1 | 1010.0 |
| 1997 | 1007.7 | 1010.4 | 1010.9 | 1009.4 | 1008.0 | 1008.1 | 1005.2 | 1008.6 | 1011.7 | 1008.2 | 1015.4 | 1014.2 | 1009.8 |
| 1998 | 1012.4 | 1015.9 | 1009.7 | 1013.0 | 1010.0 | 1011.9 | 1009.3 | 1009.6 | 1012.4 | 1014.4 | 1010.7 | 1012.1 | 1011.8 |
| 1999 | 1006.8 | 1008.3 | 1012.6 | 1012.1 | 1006.7 | 1006.6 | 1008.0 | 1009.3 | 1010.5 | 1013.1 | 1011.9 | 1011.4 | 1009.8 |
| 2000 | 1016.6 | 1009.0 | 1006.2 | 1007.4 | 1010.7 | 1006.8 | 1005.6 | 1010.5 | 1011.7 | 1012.2 | 1016.1 | 1010.4 | 1010.3 |
| 2001 | 1010.3 | 1011.1 | 1006.2 | 1009.0 | 1009.8 | 1005.3 | 1007.3 | 1011.0 | 1012.9 | 1016.0 | 1009.9 | 1012.1 | 1010.1 |
| 2002 | 1008.9 | 1011.4 | 1007.0 | 1012.4 | 1011.0 | 1008.6 | 1007.0 | 1009.3 | 1013.1 | 1011.3 | 1007.0 | 1013.9 | 1010.1 |
| 2003 | 1008.7 | 1015.7 | 1013.7 | 1010.9 | 1012.6 | 1007.2 | 1012.2 | 1008.5 | 1011.8 | 1011.3 | 1016.7 | 1008.9 | 1011.5 |
| 2004 | 1011.1 | 1007.7 | 1010.2 | 1006.8 | 1007.8 | 1007.2 | 1006.6 | 1007.4 | 1012.7 | 1014.9 | 1013.1 | 1012.4 | 1009.8 |
| 2005 | 1007.9 | 1011.2 | 1006.5 | 1008.8 | 1009.4 | 1006.1 | 1007.2 | 1007.8 | 1013.5 | 1012.8 | 1008.8 | 1006.8 | 1008.9 |
| 2006 | 1011.9 | 1013.3 | 1005.0 | 1009.5 | 1010.4 | 1009.6 | 1007.1 | 1008.3 | 1012.9 | 1015.1 | 1011.5 | 1015.3 | 1010.8 |
| 2007 | 1015.5 | 1011.7 | 1009.6 | 1011.8 | 1006.6 | 1008.3 | 1006.2 | 1007.0 | 1012.0 | 1013.7 | 1012.1 | 1011.2 | 1010.5 |
| 2008 | 1012.5 | 1010.1 | 1014.5 | 1013.1 | 1010.5 | 1010.3 | 1007.6 | 1009.0 | 1008.4 | 1013.3 | 1010.6 | 1010.0 | 1010.8 |
| 2009 | 1014.0 | 1009.9 | 1009.5 | 1010.2 | 1008.1 | 1006.9 | 1006.0 | 1008.3 | 1011.1 | 1010.3 | 1016.2 | 1009.6 | 1010.0 |
| 2010 | 1007.1 | 1012.5 | 1011.7 | 1013.2 | 1011.0 | 1008.8 | 1007.1 | 1008.9 | 1009.8 | 1015.2 | 1010.8 | 1005.3 | 1010.1 |
| 2011 | 1007.7 | 1013.4 | 1008.1 | 1007.6 | 1009.9 | 1005.6 | 1007.9 ) | 1008.1 | 1010.4 | 1012.3 | 1013.9 | 1010.7 | 1009.6 |
| 2012 | 1012.7 | 1011.0 | 1012.0 | 1010.4 | 1010.7 | 1010.8 | 1007.2 | 1010.3 | 1014.0 | 1011.7 | 1009.7 | 1009.1 | 1010.8 |
| 2013 | 1012.6 | 1011.1 | 1005.8 | 1005.0 | 1010.7 | 1009.5 | 1007.1 | 1004.2 | 1012.4 | 1015.7 | 1008.0 | 1007.8 | 1009.2 |
| 2014 | 1010.7 | 1016.3 | 1010.6 | 1011.2 | 1006.9 | 1007.8 | 1006.3 | 1008.9 | 1010.7 | 1013.9 | 1012.3 | 1005.5 | 1010.1 |
| 2015 | 1009.7 | 1011.5 | 1010.4 | 1012.8 | 1004.7 | 1007.6 | 1006.1 | 1010.9 | 1011.9 | 1008.1 | 1020.8 | 1013.0 | 1010.6 |
| 2016 | 1011.6 | 1013.3 | 1013.9 | 1010.1 | 1009.1 | 1008.9 | 1008.8 | 1006.1 | 1013.9 | 1010.8 | 1014.2 | 1012.7 | 1011.1 |
| 2017 | 1011.4 | 1008.6 | 1011.3 | 1007.0 | 1008.6 | 1007.0 | 1005.5 | 1008.4 | 1008.7 | 1016.3 | 1009.6 | 1008.4 | 1009.2 |
| 2018 | 1007.4 | 1011.6 | 1012.1 | 1009.5 | 1009.4 | 1007.5 | 1009.2 | 1008.5 | 1011.5 | 1011.8 | 1016.0 | 1011.8 | 1010.5 |
| 2019 | 1009.7 | 1012.0 | 1008.7 | 1008.8 | 1007.4 | 1007.5 | 1008.3 | 1008.4 | 1011.9 | 1015.3 | 1011.6 | 1013.0 | 1010.2 |
| 2020 | 1014.9 | 1016.0 | 1009.7 | 1010.3 | 1008.1 | 1006.1 | 1008.8 | 1008.5 | 1014.4 | 1013.0 | 1013.1 | 1009.8 | 1011.1 |
| 2021 | 1012.1 | 1005.8 | 1013.7 | 1013.4 | 1005.9 | 1008.5 | 1010.3 | 1010.2 | 1014.6 | 1015.5 | 1010.7 | 1008.7 | 1010.8 |
| 2022 | 1010.0 | 1010.7 | 1010.4 | 1011.0 | 1007.9 | 1008.7 | 1008.3 | 1004.7 | 1012.0 | 1016.5 | 1013.7 | 1008.6 | 1010.2 |
| 2023 | 1010.5 | 1015.3 | 1014.9 | 1008.2 | 1010.2 | 1006.1 | 1006.1 | 1009.0 | 1011.3 | 1009.3 | 1009.5 | 1012.9 | 1010.3 |
| 2024 | 1012.7 | 1018.3 | 1009.8 | 1013.5 ] | 1013.6 ] |
Remarks
The red lines, if any, indicate data inhomogeneity caused by changes in instrumentation, observation methods and/or site location.