Year Season NPTW Area [km**2] 1967 winter 162.06 1968 winter 131.13 1969 winter 133.36 1970 winter 73.63 1971 winter 83.64 1972 winter 85.88 1972 summer 118.49 1973 winter 25.47 1973 summer 143.07 1974 winter 86.46 1974 summer 165.78 1975 winter 74.02 1975 summer 108.96 1976 winter 71.03 1976 summer 93.47 1977 winter 84.91 1977 summer 144.64 1978 winter 185.33 1978 summer 195.04 1979 winter 168.20 1979 summer 146.16 1980 winter 151.11 1980 summer 220.04 1981 winter 181.40 1981 summer 217.42 1982 winter 148.56 1982 summer 186.11 1983 winter 143.21 1983 summer 167.91 1984 winter 119.41 1984 summer 166.41 1985 winter 121.52 1985 summer 204.76 1986 winter 111.74 1986 summer 235.96 1987 winter 173.62 1987 summer 186.19 1988 winter 153.01 1988 summer 194.56 1989 winter 114.76 1989 summer 114.53 1990 winter 111.03 1990 summer 107.15 1991 winter 117.16 1991 summer 106.67 1992 winter 123.07 1992 summer 167.34 1993 winter 97.03 1993 summer 163.30 1994 winter 165.29 1994 summer 166.09 1995 winter 129.06 1995 summer 214.31 1996 winter 185.92 1996 summer 210.52 1997 winter 139.67 1997 summer 148.45 1998 winter 95.57 1998 summer 120.55 1999 winter 63.99 1999 summer 71.15 2000 winter 91.08 2000 summer 117.35 2001 winter 57.58 2001 summer 117.62 2002 winter 99.42 2002 summer 129.54 2003 winter 120.05 2003 summer 116.14 2004 winter 131.61 2004 summer 151.21 2005 winter 133.47 2005 summer 162.20 2006 winter 113.23 2006 summer 102.79 2007 winter 87.19 2007 summer 94.79 2008 winter 135.29 2008 summer 91.86 2009 winter 88.47 2009 summer 128.44* 2010 winter 71.61 2010 summer 136.93 2011 winter 106.23 2011 summer 164.87 2012 winter 103.72 2012 summer 154.90 2013 winter 113.85 2013 summer 141.73 2014 winter 125.58 2014 summer 154.04 2015 winter 143.04 2015 summer 163.58 2016 winter 227.59 2016 summer 192.14 2017 winter 166.01 2017 summer 196.10 2018 winter 167.11 2018 summer 155.98 2019 winter 135.12 2019 summer 161.80 2020 winter 108.94 2020 summer 50.78 2021 winter 87.07 2021 summer 68.54* 2022 winter 63.17 2022 summer 54.72 2023 winter 60.64* 2023 summer 33.83* # データ中の「*」について # *がついている時期の観測は台風による時化の影響等で、 #「北太平洋回帰線水の変動」を診断するために十分なデータを得られませんでした。 # このため、啓風丸・凌風丸による観測の前後2週間以内に他の観測船や中層フロートが # 観測したデータも利用して解析を行いました。