This index captures SST variations in the cold tongue region of the equatorial Pacific Ocean (6N-6S, 180-90W), and will hereafter be referred to as the cold tongue index (CTI). Anomalies are with respect to 1950-79.
Read the following. The smoothing employed does strange things to the ends of time series. Because this series ends in the midst of a strong El Nino I have taken the liberty to make sure that the qualitative impression one gets from this plot is true to the data. Both the 1982-83 and 1997-Jan98 data have peak SST anomalies of 2.58C and at least five months of SST anomalies > 2C (see table below). Because these values are comparable I have set the peak smoothed 1997-Jan98 values to be 1.75C which is the peak value for the 1982-83 event. I will plot a new graph once the present event has ended. June 1999: I updated the CTI, but did not replot the above figure.
There is a jump in COADS SST values between November and December of 1941 that seems to be due to a step change in the composition of COADS observations at the beginning of World War ll (Folland and Parker, 1995). With the beginning of World War ll observations from United States ships comprise a significant percentage of the COADS observations, and a predominance of engine intake SST measurements in ships of United States registry gives rise to a spurious increase in SST. An image showing this step jump in global-mean SST is linked here (PostScript file). This spurious feature is removed by subtracting the global-mean SST from the CTI. Additional details of the index calculation are discussed here.
Reference:
Folland, C. K. and D. E. Parker, 1995: Correction of instrumental
biases in historical sea surface temperature data.
Quart. J. Roy. Meteor. Soc., 121, 319-367.
The time series:
In MATLAB ".mat" format
As an ASCII table. (Columns are year, month, and
CTI. -999 for missing.)
Digital values for the number of observations from the COADS for 1854-1992 are presented at the bottom of this page.
The following table lists the digital values of the CTI in hundredths of degrees Celsius. Missing data are indicated by blanks.
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
1854 -18 -3 -19 -26 -104
1855
1856 -40 -59
1857 -82 -104 10 -8 36
1858 19 -14 11 40 30 2
1859 -59 -41 -40 -83 -27
1860 -56 -50 -70 -60 -43
1861 -29 92 -56
1862 37 94 -27 -94
1863 -81 -40
1864 11 179 152
1865 -14
1866
1867 305
1868 -145 43 22 45 3 226 281 291
1869 8 0 -146 15 -28 -89
1870 -119 -6 64 30 -16 -76 -79 -80 -103 57
1871 -16 51 14 30 -29 73 -18 31 20 -1 -19
1872 -9 -10 -34 45 -13 -44 13 -62 -36 -92 -51
1873 -69 -75 -22 -17 8 21 -34 -48 -105
1874 -73 -74 -30 -87 5 -26 -62 35 -72 -86 -124
1875 9 -89 -5 -52 -30 16 -6 -50 -25 -54 -116 -41
1876 47 -45 -137 -112 4 80 86 37 100 98 101
1877 141 55 51 128 84 142 47 195 171 199 25 270
1878 281 201 77 46 34 31 -1 -45 3 -53
1879 -20 52 4 3 -27 -68 -19 -23 23 -45 -30 -37
1880 -114 34 7 179 16 2 23 53 119 25 47
1881 50 26 50 34 29 40 45 -5 67 -14 -7 -13
1882 -13 -36 30 31 50 -35 -36 -15 21 -40 -47 -16
1883 -42 -11 79 83 54 -2 14 52 27 22 0 20
1884 -18 4 63 -4 70 -3 27 47 62 149 122 117
1885 75 11 50 31 42 77 -14 36 94 81 125 131
1886 48 -33 -16 -127 -69 -89 -79 -63 -74 -71 -75
1887 -86 -70 -14 -53 29 -31 -28 -41 17 -26 54 42
1888 78 148 80 87 105 91 90 92 157 193 218 231
1889 249 188 57 77 54 24 -17 -55 -71 -77 -91 -42
1890 -23 33 -89 -4 -4 -34 -38 -30 0 -21 -56 61
1891 54 40 28 78 57 68 47 104 -20 31 70 22
1892 30 3 2 -20 -36 -53 -41 -69 -74 -77 -36
1893 -98 -103 -68 -55 -74 -62 -38 -60 -49 -16 -56 -35
1894 -51 21 -20 -42 17 -22 63 3 -3 -53 3 -36
1895 0 -56 16 25 42 51 20 52 99 74 112 84
1896 85 27 54 28 24 41 122 135 115 135 185 209
1897 160 161 75 -39 -10 0 55 -35 17 -23 -7 -19
1898 14 -58 -49 -54 -22 -45 -45 -66 -31 -36 -41 -35
1899 -45 -12 -65 0 -14 -3 12 58 85 93 161 164
1900 151 145 108 80 90 77 81 57 49 74 22 71
1901 56 32 5 32 5 9 -61 -5 28 32 45 31
1902 51 68 48 71 72 94 184 167 182 194 205 209
1903 196 155 119 48 52 20 -19 -42 -15 7 -35 -28
1904 13 28 35 5 8 67 114 110 85 146 119 148
1905 159 129 135 98 169 162 115 118 196 178 164 137
1906 145 81 48 80 16 -31 -47 -97 -35 -70 -72 21
1907 -5 -19 -46 -14 38 52 96 52 88 44 62 63
1908 -11 97 27 10 -6 -83 -69 -13 -70 -64 -53 -66
1909 -46 -83 -9 -41 -67 -53 -9 -62 -31 -95 -100 -86
1910 -83 -19 -96 -113 -52 -62 -21 -41 -51 -8 -39 -3
1911 -44 -55 -44 -35 19 28 88 84 65 138 164 213
1912 148 119 62 88 25 -18 15 -7 90 47 28 9
1913 -39 23 27 -3 -40 53 49 18 57 48 72 128
1914 123 72 70 78 -1 -5 109 64 127
1915 114 95 -15 -8 -56
1916 -55 37 70 -200 -94 -79 -85 -63
1917 -67 33 77 117 94 98 23
1918 15 133 239 176 244 308
1919 203 117 132 77 59 54 61 162
1920 99 17 68 118 4 -8 48 1 -5 32
1921 87 63 -46 -3 -29 18 6 -13 49 10 1 49
1922 -8 21 33 49 53 -78 25 -27 8 -42 -46 27
1923 6 -6 48 31 73 64 55 71 118 100 132 122
1924 49 62 57 -18 -79 -15 -85 -64 -55 -63 -50 -18
1925 -71 -41 39 -5 18 65 80 82 90 73 134 137
1926 123 72 74 67 70 -13 37 0 -32 -58 -31 -20
1927 69 64 -23 -21 7 -3 -28 12 37 46 36 59
1928 32 12 7 13 35 -36 -7 -19 0 -8 10 10
1929 -34 -1 36 39 45 39 32 28 42 47 68 36
1930 34 30 37 58 57 6 73 63 106 134 168 151
1931 168 111 98 92 29 5 1 5 -10 -59 -16 -25
1932 7 49 72 35 94 40 -6 -17 -2 24 12 8
1933 35 67 18 41 -31 -42 -77 -65 -40 -53 -18 -46
1934 23 7 32 34 22 -9 -25 29 18 13 33 -21
1935 -31 -14 8 -33 -26 -22 -45 32 53 31 34 -10
1936 62 44 32 17 33 -32 -14 -10 -2 68 20 40
1937 -13 -31 -3 -22 -36 -46 -15 -74 -13 -18 6 2
1938 -44 -19 -46 -51 -52 -91 -112 -92 -143 -65 -150 -18
1939 -10 38 59 28 -30 80 59 -69 -19 75
1940 167 203 237 66 78 33 76 92 -10 151
1941 150 106 1 85 43 130 83 100 69 142 174 232
1942 125 97 42 41 7 -15 -41 -77 -96 -85 -97 -77
1943 -84 -78 -85 -57 -51 -33 -8 6 -15 -63 -52 -36
1944 -39 -8 -9 -4 2 6 28 9 4 -50 -40 -38
1945 -79 -52 -117 -139 -51 -80 -45 -22 -35 17 17
1946 10 -14 45 42 -98 -43 -51 51 -11 -41 38
1947 39 18 16 27 37 41 -23 -44 -14 -61 -21 -8
1948 39 34 35 29 39 -37 -58 -22 -37 -44 -27 16
1949 -69 -13 -4 48 24 -37 -19 -47 -86 -109 -121 -62
1950 -123 -143 -33 -52 -85 -66 -109 -41 -96 -82 -102 -37
1951 -56 -65 -47 49 50 48 130 101 51 109 143 83
1952 42 34 -4 23 -18 -64 -54 -67 -24 -33 -26 -22
1953 38 35 32 85 59 47 46 9 85 19 27 -10
1954 -33 -18 5 -127 -110 -121 -116 -100 -96 -113 -88 -101
1955 -43 0 -65 -55 -115 -105 -104 -85 -129 -147 -185 -147
1956 -120 -54 -46 -28 -43 -24 -27 -63 -53 -50 -65 -66
1957 -72 -14 20 57 101 116 122 111 94 74 121 137
1958 124 119 78 32 15 29 31 4 -32 -1 -6 2
1959 -1 -15 27 34 14 -19 -34 -26 -35 36 10 -1
1960 -12 -20 0 7 -18 -25 -33 -18 13 -37 -56 -21
1961 -13 42 -3 -2 -11 12 -69 -66 -94 -99 -37 -39
1962 -22 -12 -29 -82 -42 -26 -26 -20 -43 -50 -60 -80
1963 -46 -31 6 9 12 21 73 79 77 72 84 93
1964 59 11 -14 -65 -123 -116 -47 -56 -48 -45 -81 -87
1965 -6 18 35 54 114 145 149 173 167 167 172 155
1966 133 80 27 17 -5 1 21 -3 -22 -5 -43 -36
1967 -40 -12 -21 -19 25 36 -21 -99 -84 -74 -54 -44
1968 -65 -70 -62 -36 -43 -4 44 66 57 51 65 87
1969 77 28 56 60 123 76 40 69 77 100 113 133
1970 124 46 3 27 -16 -64 -128 -112 -80 -73 -121 -116
1971 -80 -74 -46 -28 -23 -31 -29 -54 -41 -64 -49 -65
1972 2 22 28 69 112 121 173 201 186 218 217 222
1973 181 89 28 -36 -50 -85 -92 -90 -79 -78 -100 -95
1974 -100 -59 -27 -7 14 20 9 6 -5 -34 -23 -55
1975 -34 -32 -18 17 -26 -72 -53 -58 -69 -98 -99 -120
1976 -91 -24 -7 2 54 104 108 146 126 141 143 94
1977 107 66 54 -17 14 31 15 11 21 59 67 62
1978 64 46 3 -29 -23 -33 -40 -49 -23 -22 -5 40
1979 7 10 22 40 42 47 18 27 96 56 39 38
1980 39 4 27 10 50 48 -1 -5 26 -4 53 61
1981 -56 -48 -6 -36 4 4 -26 -60 14 16 -12 49
1982 29 14 13 41 84 111 101 122 164 198 223 246
1983 245 199 157 127 154 126 85 60 32 -31 -51 -53
1984 -65 -33 -13 -13 -27 -59 -35 -33 -13 -51 -58 -108
1985 -69 -95 -73 -59 -54 -57 -51 -34 -31 -43 -28 -33
1986 -48 -39 -19 -11 -6 2 21 31 72 86 109 102
1987 119 115 114 102 108 122 135 137 156 125 116 101
1988 63 21 7 -47 -97 -137 -142 -133 -91 -147 -156 -155
1989 -140 -92 -94 -65 -45 -38 -37 -41 -22 -25 -26 -11
1990 -4 14 18 27 33 8 -7 11 27 22 13 26
1991 29 11 14 6 58 79 72 44 44 88 126 146
1992 143 131 124 127 130 56 40 18 12 11 16 32
1993 27 37 56 94 113 73 57 33 55 53 39 36
1994 21 -6 3 -8 23 30 6 21 44 73 102 109
1995 91 67 26 -5 -18 -14 -20 -47 -53 -68 -78 -71
1996 -61 -68 -33 -49 -44 -38 -21 -27 -25 -28 -30 -57
1997 -48 -29 0 35 95 127 167 199 220 233 252 248
1998 232 182 136 85 60 -40 -67 -71 -63 -96 -98 -126
1999 -129 -96 -65 -80 -51
Modern record (1950-present):
Historical record (1854-present):
Index values for the years 1854 to 1981 were calculated in the following manner. SST anomalies were calculated for each month and year by subtracting the smoothed climatology from the COADS SST data. CTI and global-mean SST values were calculated as the average anomaly in the two averaging regions, weighted by the number of observations. The global-mean SST was then subtracted from the CTI to remove the spurious step jump in SST in December 1941.
The sensitivity of the CTI to the choice of climatology periods was explored by calculating CTI anomalies with respect to both the 1900-79 and 1950-79. CTI anomalies with respect to 1900-79 and 1950-79 are shown on the top and bottom of the following figure, respectively, and are largely the same for the two calculations.
Index values for the years beginning in 1982 were calculated in the following manner. Optimal interpolation (OI) monthly-mean SST values were obtained from NOAA NCEP (Reynolds and Smith, 1994, J. Climate, 7, 929-948). The 1-degree latitude-longitude data were averaged into 2-degree latitude-longitude regions, and the smoothed COADS climatology (1950-79) subtracted to produced anomalies. The global-average SST was subtracted from the CTI values as in the calculation for the earlier period.
COADS- and OI-based CTI values for the common period 1982-92 are shown in red and black, respectively, below, with the OI values extended through 1996. The two time series are correlated at 0.96 . A similar comparison for the "Nino3" SST index is shown in Fig. 14 of Smith et al. (1996, J. Climate, 7, 1403-1420; hereafter SRLS).
The largest discrepancy between the COADS- and OI-based CTI is found between August 1988 and February 1989. Average SST anomaly maps for these fields are shown below. The shading interval is 0.4C, with gray for SST anomalies < 0.4C in magnitude. The OI analysis looks plausible. The evolution of the cold SST anomalies in OI and ship data are shown in a longitude-time diagram in SRLS (their Fig. 17).
As the final step, anomalies of the CTI were recalculated with respect to the period 1950-79.
The number of observations time series is available in MATLAB ".dat" format. ["load ctinob18541995.dat" will read the data into the variable "ctinob18541995" . ] The file is written in ASCII and can probably be easily read with any software.
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
1854 1 0 0 0 0 0 0 22 17 0 38 20
1855 0 0 0 0 0 0 0 0 0 0 0 0
1856 0 0 0 0 0 0 0 0 0 0 1 37
1857 0 0 17 17 0 8 0 0 22 22 0 0
1858 37 0 0 42 6 28 0 0 0 0 21 27
1859 29 7 27 46 34 0 0 0 0 0 0 0
1860 67 0 0 31 6 0 0 0 0 0 21 24
1861 0 0 30 0 0 0 1 0 20 0 0 0
1862 0 0 51 0 0 0 5 0 5 0 42 0
1863 0 0 0 5 14 0 0 0 0 0 0 0
1864 0 0 0 0 0 11 0 13 0 0 67 0
1865 0 0 0 0 0 0 0 0 0 0 1 0
1866 0 0 0 0 0 0 0 0 0 0 0 0
1867 0 0 0 0 0 13 0 0 0 0 0 0
1868 4 0 2 10 0 10 11 0 10 10 10 0
1869 0 0 0 0 0 16 4 0 28 12 5 5
1870 13 29 9 12 0 21 60 1 5 0 20 8
1871 0 18 29 11 2 45 4 7 33 4 6 5
1872 16 36 6 9 56 0 5 13 38 16 39 23
1873 12 139 10 0 0 7 48 55 0 41 136 28
1874 13 66 39 8 0 24 8 34 6 98 41 4
1875 7 52 162 102 45 6 86 2 77 17 37 68
1876 1 45 19 30 0 13 27 54 38 106 99 18
1877 42 66 11 7 53 4 3 28 61 23 1 21
1878 32 1 0 90 10 0 18 59 31 74 4 92
1879 1 65 48 10 1 35 14 71 50 61 149 39
1880 25 118 47 1 0 87 10 35 88 88 92 75
1881 49 89 74 140 23 3 158 118 19 153 110 72
1882 126 84 26 60 77 45 69 21 65 39 85 77
1883 85 105 58 25 27 96 112 57 100 103 117 124
1884 154 80 21 29 90 122 50 30 160 62 128 109
1885 115 129 55 75 104 63 146 33 132 25 86 8
1886 35 103 66 16 0 144 65 63 82 306 159 115
1887 72 40 24 156 26 108 163 111 57 74 148 125
1888 128 36 181 130 293 86 130 167 107 282 101 75
1889 85 113 116 114 98 83 85 161 14 38 39 87
1890 25 8 17 42 73 75 38 76 176 42 105 72
1891 141 102 204 156 156 115 113 7 74 94 35 186
1892 25 82 215 77 22 82 0 103 45 95 75 25
1893 16 94 90 64 37 23 35 97 86 10 79 29
1894 206 148 136 23 63 51 21 73 73 162 62 135
1895 11 144 79 11 21 47 39 94 35 150 125 116
1896 78 271 19 120 176 90 11 66 103 86 146 82
1897 92 90 44 67 398 248 85 93 360 112 71 107
1898 117 25 180 58 125 141 57 80 96 62 139 128
1899 72 82 24 108 53 60 53 102 181 26 93 73
1900 109 153 83 103 57 87 80 39 49 92 93 107
1901 76 288 108 125 256 123 64 68 99 83 102 143
1902 102 53 156 147 102 57 78 80 79 147 201 180
1903 44 54 92 93 96 59 58 106 83 59 44 122
1904 69 61 111 66 100 105 108 33 112 82 84 76
1905 36 63 17 31 120 24 66 41 37 37 78 43
1906 33 53 89 41 103 66 19 59 46 24 30 76
1907 45 33 27 37 24 35 11 23 45 14 45 65
1908 45 48 80 51 58 17 83 62 39 91 164 113
1909 28 54 91 124 47 165 238 124 141 132 194 64
1910 179 172 71 26 41 116 175 225 63 209 54 127
1911 335 234 117 81 83 55 180 131 4 143 190 67
1912 143 97 29 161 88 86 152 156 79 152 34 206
1913 89 234 217 84 47 238 162 23 125 168 54 191
1914 103 30 147 61 17 57 45 27 0 34 0 0
1915 8 0 0 14 0 0 2 0 28 0 0 5
1916 0 0 30 0 10 1 0 20 20 8 28 70
1917 185 0 5 0 13 30 6 0 7 8 0 0
1918 0 0 56 0 6 0 11 16 0 0 25 4
1919 0 9 0 2 20 0 23 0 9 18 15 8
1920 0 0 21 21 9 16 22 26 26 33 17 20
1921 20 35 68 55 79 40 48 91 32 47 50 55
1922 117 51 47 18 51 36 43 84 49 47 69 83
1923 101 54 66 86 63 94 109 60 76 94 107 67
1924 71 63 59 65 65 44 43 78 139 26 141 143
1925 79 33 52 45 135 82 63 29 79 70 101 58
1926 46 56 73 78 63 73 71 141 83 125 120 131
1927 111 196 110 112 136 173 168 109 158 164 124 112
1928 68 150 166 164 45 90 71 109 136 107 191 92
1929 94 83 142 106 72 89 126 176 99 220 181 113
1930 195 171 203 150 100 56 139 152 116 114 137 167
1931 188 99 150 215 73 112 105 132 127 72 140 176
1932 119 221 152 111 101 161 84 72 188 114 101 121
1933 166 95 133 134 127 148 100 134 174 67 161 133
1934 115 102 194 141 85 114 128 132 117 140 109 100
1935 158 164 106 79 119 91 135 81 88 151 83 101
1936 126 140 192 65 91 80 61 106 94 71 73 76
1937 137 84 62 64 75 122 85 58 94 29 94 32
1938 78 32 45 16 57 51 9 22 7 1 7 31
1939 57 2 0 14 40 0 8 12 35 36 21 19
1940 42 20 12 4 37 17 59 0 0 2 3 29
1941 48 8 2 4 5 9 27 139 71 168 73 19
1942 192 331 415 135 249 100 225 112 87 210 178 127
1943 123 193 124 164 184 183 161 160 472 238 336 246
1944 426 261 215 185 141 92 139 209 358 199 217 117
1945 138 108 120 34 68 0 35 47 32 44 53 19
1946 0 9 20 36 23 12 104 52 18 32 45 88
1947 217 191 127 85 94 113 71 146 81 42 74 52
1948 159 85 88 134 56 73 73 97 70 112 59 38
1949 74 59 139 96 89 142 406 110 164 137 101 160
1950 142 412 258 151 261 137 310 261 204 212 319 182
1951 296 360 161 148 128 111 157 152 460 164 177 202
1952 222 233 284 295 297 756 266 503 215 228 169 135
1953 209 374 213 91 302 208 145 264 187 188 268 223
1954 119 115 172 159 170 268 174 242 134 244 137 239
1955 162 205 157 184 246 229 171 253 214 291 363 295
1956 197 233 316 257 153 250 239 452 458 372 457 277
1957 453 315 530 515 338 329 294 204 326 686 450 419
1958 298 528 396 916 549 373 431 373 378 559 458 312
1959 339 387 408 458 397 395 392 310 325 215 412 528
1960 417 381 484 401 343 378 483 399 424 450 556 680
1961 512 462 765 572 692 590 589 575 583 949 586 565
1962 557 489 580 790 725 675 577 499 514 650 544 533
1963 559 356 644 568 584 559 486 583 433 514 423 614
1964 651 738 745 462 445 528 602 701 681 669 639 603
1965 713 422 685 577 603 610 420 634 606 524 616 575
1966 653 656 803 666 701 514 515 546 770 685 939 581
1967 730 880 954 984 669 641 791 840 740 717 755 656
1968 825 572 894 847 881 753 679 581 759 852 568 658
1969 619 659 773 632 639 632 766 586 693 606 1050 616
1970 608 615 766 746 824 684 581 560 672 733 614 495
1971 643 737 691 816 630 676 690 572 660 675 630 609
1972 681 579 672 749 596 535 556 945 711 567 743 666
1973 772 876 965 617 669 768 658 623 798 735 835 743
1974 841 758 731 706 1157 597 735 774 797 1262 1067 858
1975 748 707 674 827 904 919 874 693 886 679 577 538
1976 599 606 734 644 742 679 774 799 680 651 802 729
1977 646 628 753 800 600 660 530 733 590 675 647 573
1978 620 557 595 652 558 329 673 531 477 424 503 614
1979 738 792 483 588 559 608 589 589 579 597 582 584
1980 1472 1377 1100 892 998 751 664 881 1011 1145 882 765
1981 725 672 980 548 957 653 957 633 767 736 754 875
1982 941 1059 757 877 662 719 714 1044 887 796 1442 2419
1983 1488 690 1025 834 763 742 757 771 600 722 752 676
1984 863 1509 1403 627 599 861 711 740 738 774 1061 918
1985 796 779 655 1047 664 936 783 786 673 1085 1700 1345
1986 1330 1229 1492 905 1137 1623 1579 1736 1589 1719 1757 1705
1987 3051 2124 2133 1773 1850 2188 2001 2014 1546 2370 3082 3350
1988 2859 1541 1913 2014 1572 1753 2378 2891 3140 2653 2482 2486
1989 3227 2326 2100 2686 2509 2091 2532 2158 2248 2328 2400 2941
1990 4013 3433 3154 3077 4200 3465 3348 3964 5537 5281 4476 8362
1991 6842 5239 4527 4684 4175 1766 1511 1455 1687 1296 2122 2537
1992 2486 2361 2534 2653 2354 1772 1548 1101 1861 1525 2003 2648
1993 2594 1694 2649 3121 3288 3647 3047 3891 3248 4404 2430 2362
1994 2369 2033 1408 1594 1837 3154 2737 3454 3901 4357 4335 3654
1995 2878 3421 2672 2159 2582 2704 2951 3982 4820 4896 4748 5168