TNI (Trans-Niño Index) and N3.4 (Niño 3.4 Index)

The Climate Diagnostics Center (CDC) creates a downloadable ASCII file of area-averaged SSTs for Niño 3.4 region that is updated on a monthly basis.

Note: the CDC values are area-averaged SSTs. See below for the up-to-date CAS file.


Regression of global SST anomalies with TNI for 1900-1976 in °C. Values exceeding 0.10°C are hatched and less than -0.10°C are stippled. The contours are ±0.05°C, ±0.10°C, ±0.15°C, etc. (The TNI is defined and discussed below.)

(For a view of the first printed map of the Pacific Ocean, see Ortelius's Maris Pacifici.)


 

Indices, statistics, and selected figures from

Indices of El Niño Evolution

Kevin E. Trenberth¹, and David P. Stepaniak¹

J. Climate, 14, 1697-1701.

Abstract

To characterize the nature of El Niño-Southern Oscillation (ENSO), sea surface temperature (SST) anomalies in different regions of the Pacific have been used. We suggest that an optimal characterization of both the distinct character and the evolution of each El Niño or La Niña event requires at least two indices: (i) SST anomalies in the Niño 3.4 region (referred to as N3.4), and (ii) a new index we call the Trans-Niño Index (TNI), which is given by the difference in normalized anomalies of SST between Niño 1+2 and Niño 4 regions. The first index can be thought of as the mean SST throughout the equatorial Pacific east of the dateline and the second index is the gradient in SST across the same region. Consequently they are approximately orthogonal. TNI leads N3.4 by 3 to 12 months prior to the climate shift in 1976/77 and also follows N3.4 but with opposite sign 3 to 12 months later. However, after the 1976/77 shift, the sign of the TNI leads and lags are reversed.

(A link to an online version of the full text is provided here.)


¹National Center for Atmospheric Research
P. O. Box 3000
Boulder, CO 80307

The National Center for Atmospheric Research is sponsored by the National Science Foundation.

In addition to NCAR's postal address, Kevin E. Trenberth may be contacted via:

email: trenbert@cgd.ucar.edu
voice: (303) 497 1318
fax: (303) 497 1333


Contents


SST Data

For the period January 1871 to October 1981 we employed the HADISST data set developed by the Hadley Centre for Climate Prediction and Research, The Meteorological Office, United Kingdom. HADISST may be obtained (under a proprietary, though at no cost, licensed agreement) through the Data Support Section (DSS) of the Scientific Computing Division (SCD) at the National Center for Atmospheric Research (NCAR) (see ds277.3). The HADISST data set represents monthly total SSTs archived on a 1°x1° 360x180 grid beginning at 0.5°E and 89.5°N. The precursor of HADISST is GISST2.3b – GISST2.3b is discussed at length by Hurrell and Trenberth (1999) (see references below).

For the period November 1981 to September 2000² we employed the optimum interpolation (OI) analyses from the National Centers for Environmental Prediction (NCEP) (Reynolds and Smith 1994, see also Hurrell and Trenberth 1999). The NCEP OI data set represents monthly total SSTs archived on a 1°x1° 360x180 grid beginning at 179.5°W and 89.5°S, and may be obtained from DSS at NCAR (see ds277.0).

We reordered the HADISST and NCEP data to a common 1°x1&deg grid beginning at 0.5°E and 89.5°S, which allows for straight forward calculation of area averages across the International Dateline and the Equator. All calculations reported here were carried out at full spatial (1°x1&deg) and temporal (monthly) resolution. (A netCDF file containing these combined data sets may be made available upon request. However, it is a large file, on the order of 400Mb.)

² The period November 1981 to September 2000 has been updated though October 2001. See below.

Up to Contents


Geographic Extent of Currently Defined Niño Regions

The following table lists the geographic extent of Niño regions described in the NCEP Climate Diagnostics Bulletin (and also at the NCEP CPC web site Monthly Atmospheric and SST Indices. (What is reported as Niño 3.5 at the CPC website is a typo – it should read Niño 3.4) The outlines of the Niño 1+2, 3.4 and 4 regions are shown in the figure at the top of this web page.

Niño Region Range Longitude Range Latitude
1+2 90°W-80°W 10°S-0°
3 150°W-90°W 5°S-5°N
3.4 170°W-120°W 5°S-5°N
4 160°E-150°W 5°S-5°N

Up to Contents


Standard Deviations of Raw and Smoothed Time Series

The standard deviations listed below are for area-averaged anomalies over the climatological period 1950-1979, before (`Raw'), and after a 5-month running mean is applied ('Smoothed'). (The corresponding means are for all practical purposes identically zero.)

 

Standard Deviation (°C)
Niño Region Raw Smoothed
1+2 0.917 0.822
3.4 0.745 0.697
4 0.567 0.534

Up to Contents


TNI (Trans-Niño Index)

Computational Recipe:
  • Compute area averaged total SST from Niño 1+2 region.
  • Compute area averaged total SST from Niño 4 region.
  • Compute monthly climatologies (1950-1979) for area averaged total SST from Niño 1+2 region, and Niño 4 region, and subtract climatologies from area averaged total SST time series to obtain anomalies.
  • Normalize each time series of anomalies by their respective standard deviations over the climatological period 1950-1979.
  • Define the raw TNI as Niño 1+2 normalized anomalies minus Niño 4 normalized anomalies.
  • Smooth the raw TNI with a 5-month running mean.
  • Normalize the smoothed TNI by its standard deviation over the climatological period 1950-1979. (The smoothed TNI has a standard deviation of 0.818 over the climatological period 1950-1979.)
  • Thus, TNI = (Niño 1+2N - Niño 4N) S,N where N indicates normalized and S smoothed.
The value -9.999 denotes `missing' data.

TNI
        Jan    Feb    Mar    Apr    May    Jun    Jul    Aug    Sep    Oct    Nov    Dec
1871  0.013  0.089  0.042  0.117  0.195  0.285  0.250  0.279  0.266  0.177  0.144  0.115
1872 -0.114 -0.125 -0.161 -0.120 -0.050  0.235  0.327  0.404  0.479  0.638  0.580  0.475
1873  0.320  0.219 -0.046 -0.029 -0.002  0.125  0.041  0.168  0.086 -0.026 -0.140 -0.131
1874 -0.080 -0.102  0.157  0.213  0.286  0.201  0.380  0.422  0.743  0.947  1.056  0.948
1875  0.707  0.633  0.530  0.562  0.531  0.574  0.384  0.265 -0.023 -0.087 -0.206 -0.304
1876 -0.418 -0.276 -0.244 -0.273 -0.199 -0.047  0.103  0.360  0.707  0.832  0.814  0.548
1877  0.190 -0.174 -0.508 -0.950 -0.973 -0.932 -0.742 -0.426  0.122  0.409  0.593  0.610
1878  0.377  0.163 -0.124 -0.572 -0.772 -0.698 -0.625 -0.364 -0.093  0.073  0.089  0.105
1879 -0.108 -0.042 -0.045  0.176  0.475  0.787  0.918  1.131  1.226  1.276  1.197  1.283
1880  1.032  0.769  0.561  0.507  0.468  0.652  0.880  0.980  1.063  0.848  0.572  0.197
1881 -0.269 -0.662 -0.807 -0.893 -0.826 -0.758 -0.622 -0.363 -0.111 -0.071  0.040  0.147
1882  0.006 -0.221 -0.396 -0.638 -0.886 -1.219 -1.166 -0.970 -0.598 -0.315 -0.162 -0.301
1883 -0.565 -0.715 -0.670 -0.409 -0.357 -0.303 -0.302 -0.260 -0.192 -0.078  0.057  0.037
1884 -0.030 -0.060 -0.129 -0.030 -0.136 -0.318 -0.487 -0.375 -0.275  0.130  0.406  0.520
1885  0.287  0.024 -0.554 -1.029 -1.291 -1.297 -1.372 -1.213 -1.018 -0.959 -1.130 -1.353
1886 -1.635 -1.772 -1.720 -1.494 -1.140 -0.696 -0.249  0.070  0.507  0.843  0.951  0.722
1887  0.480  0.321  0.184  0.194  0.314  0.419  0.392  0.275  0.235  0.253  0.320  0.137
1888  0.011  0.074  0.123  0.268  0.321  0.310  0.748  0.813  0.606  0.700  0.863  0.359
1889  0.168  0.201  0.100  0.021  0.002 -0.056 -0.150  0.077  0.324  0.780  1.588  2.201
1890  2.221  2.084  1.704  1.013  0.463  0.588  0.821  1.018  1.140  1.177  0.960  0.702
1891  0.504  0.482  0.652  0.759  0.923  0.932  0.725  0.386  0.111 -0.137 -0.072 -0.012
1892  0.054  0.186  0.120 -0.132 -0.198 -0.245 -0.282 -0.025  0.290  0.322  0.252  0.209
1893  0.133  0.171  0.446  0.773  1.120  1.351  1.481  1.690  2.029  2.075  2.185  2.272
1894  2.116  1.867  1.756  1.557  1.345  1.227  1.255  1.261  1.238  1.146  1.132  0.872
1895  0.517  0.331  0.225  0.042  0.015  0.029 -0.005  0.175  0.311  0.437  0.707  0.866
1896  0.628  0.584  0.571  0.644  0.480  0.531  0.498  0.361  0.266  0.431  0.407  0.382
1897  0.512  0.510  0.487  0.509  0.400  0.197 -0.127 -0.130  0.024  0.217  0.460  0.703
1898  0.621  0.372  0.160 -0.143 -0.091  0.120  0.105  0.322  0.728  0.953  1.153  1.555
1899  1.739  1.670  1.396  1.126  0.698  0.610  0.760  0.725  0.473  0.354  0.165 -0.057
1900  0.014  0.156  0.402  0.415  0.154 -0.203 -0.502 -0.781 -0.966 -1.143 -1.280 -1.212
1901 -1.226 -1.291 -1.299 -1.207 -1.295 -1.258 -1.109 -0.721 -0.132  0.423  1.002  1.312
1902  1.600  1.293  0.938  0.630  0.431  0.018 -0.087  0.118  0.181  0.069 -0.112 -0.602
1903 -1.290 -1.795 -1.944 -1.979 -1.632 -1.527 -1.456 -1.429 -1.163 -0.918 -0.042  0.383
1904  0.472  0.368  0.591  0.078 -0.041  0.225  0.431  0.205  0.585  0.465  0.216 -0.211
1905 -0.363 -0.873 -0.557 -0.249 -0.021  0.113 -0.033 -0.271 -0.319 -0.456 -0.496 -0.264
1906 -0.702 -1.183 -1.019 -1.123 -1.428 -1.489 -1.340 -1.303 -1.295 -0.910 -0.315 -0.036
1907 -0.038  0.078 -0.124 -0.327 -0.763 -1.141 -1.209 -1.069 -1.001 -0.814 -0.322 -0.212
1908 -0.028 -0.175 -0.302 -0.256 -0.380 -0.556 -0.527 -0.230 -0.334 -0.112  0.189  0.444
1909  0.491  0.418  0.017 -0.364 -0.500 -0.664 -0.775 -0.355 -0.020  0.216  0.374  0.640
1910  0.591  0.674  0.671  0.670  0.634  0.651  0.630  0.658  0.692  0.642  0.613  0.466
1911  0.352  0.285  0.238  0.324  0.394  0.917  1.382  1.852  1.949  2.170  1.680  1.216
1912  0.672  0.384  0.078 -0.058 -0.433 -0.396 -0.374 -0.453 -0.506 -0.121  0.195  0.230
1913 -0.009 -0.186 -0.372 -0.555 -0.461  0.077  0.508  1.055  1.231  1.436  1.349  1.083
1914  0.678  0.084 -0.392 -0.689 -0.554 -0.632 -0.139  0.279  0.562  0.739  0.838  0.628
1915  0.270  0.151  0.119  0.225  0.219  0.164 -0.126 -0.523 -0.793 -0.935 -0.913 -0.934
1916 -0.948 -1.101 -1.371 -1.729 -1.841 -1.768 -1.596 -1.238 -0.763 -0.282  0.037  0.114
1917  0.195  0.398  0.492  0.457  0.772  0.965  0.851  0.601  0.583  0.256  0.151  0.216
1918  0.396  0.689  1.230  1.639  2.022  2.236  2.119  1.872  1.633  1.271  0.855  0.479
1919 -0.052 -0.395 -0.604 -0.595 -0.556 -0.493 -0.399 -0.252 -0.092 -0.009  0.418  0.613
1920  0.472  0.409  0.404 -0.103 -0.864 -1.139 -1.528 -2.084 -1.780 -0.980 -0.715 -0.281
1921  0.512  0.395  0.311  0.326  0.093 -0.491 -0.658 -0.848 -0.657 -0.628 -0.327  0.056
1922 -0.014 -0.089 -0.150 -0.326 -0.837 -0.953 -1.311 -1.245 -1.329 -0.950 -0.570 -0.129
1923 -0.144  0.261  0.288  0.357  0.440  0.425  0.166 -0.109 -0.560 -0.942 -1.060 -1.127
1924 -1.339 -1.323 -1.435 -1.477 -1.439 -1.017 -0.842 -0.530 -0.050  0.077  0.401  1.022
1925  1.441  1.664  1.950  2.162  1.738  1.359  0.960  0.785  0.278  0.157  0.206  0.065
1926 -0.145 -0.111 -0.305 -0.724 -0.695 -0.789 -0.993 -0.737 -0.375 -0.185  0.102  0.305
1927  0.296  0.105  0.078 -0.095 -0.293 -0.506 -0.478 -0.714 -0.534 -0.500 -0.588 -0.652
1928 -0.531 -0.681 -0.672 -0.707 -0.846 -1.013 -1.133 -1.148 -1.075 -0.901 -0.739 -0.497
1929 -0.322  0.076  0.317  0.349  0.146  0.026 -0.180 -0.451 -0.573 -0.685 -0.981 -1.240
1930 -1.363 -1.260 -0.905 -0.515 -0.279  0.072  0.080  0.234  0.256  0.439  0.366  0.183
1931 -0.110 -0.172 -0.611 -1.038 -1.056 -1.284 -1.268 -0.868 -0.544 -0.250  0.401  0.845
1932  0.883  1.128  1.408  1.371  1.269  1.209  0.979  0.669  0.280  0.077 -0.135  0.086
1933  0.110  0.200  0.081  0.357  0.053  0.057  0.177  0.493  0.613  1.088  1.390  1.484
1934  1.621  1.636  1.581  1.479  1.226  1.124  1.088  0.856  0.522  0.409 -0.022 -0.683
1935 -0.748 -0.370  0.031  0.137  0.466  0.363  0.085 -0.305 -0.317 -0.141 -0.178 -0.224
1936 -0.178 -0.234 -0.481 -0.443 -0.491 -0.525 -0.441 -0.265 -0.078 -0.308 -0.092 -0.201
1937 -0.675 -0.743 -0.664 -0.903 -1.030 -0.751 -0.822 -0.745 -0.948 -0.845 -0.867 -0.979
1938 -1.050 -1.033 -0.772 -0.771 -1.064 -0.957 -0.736 -0.630 -0.325  0.073  0.328  0.669
1939  0.485  0.376  0.609  0.566  0.221  0.191 -0.282 -0.158 -0.278 -0.284 -0.428 -0.137
1940 -0.670 -0.770 -0.757 -0.846 -0.914 -0.750 -0.707 -0.704 -0.763 -0.823 -0.950 -0.891
1941 -0.849 -0.684 -0.522 -0.586 -0.943 -1.005 -0.979 -0.926 -0.643 -0.265 -0.169 -0.249
1942 -0.355 -0.802 -0.904 -1.153 -1.362 -1.467 -1.129 -1.065 -0.755 -0.174  0.713  1.219
1943  1.365  1.548  1.450  0.930  0.613  0.452  0.163  0.277  0.287  0.293  0.244  0.400
1944  0.200  0.171 -0.002  0.092 -0.116 -0.230 -0.284 -0.268 -0.462 -0.558 -0.598 -0.310
1945 -0.056  0.430  1.049  1.401  1.281  1.364  1.438  1.443  1.508  1.585  1.325  0.720
1946  0.124 -0.241 -0.559 -1.094 -1.174 -1.264 -1.385 -1.474 -1.136 -1.121 -0.960 -0.848
1947 -0.847 -0.689 -0.535 -0.927 -1.092 -1.101 -0.895 -0.507  0.365  0.571  0.667  0.727
1948  0.454  0.045 -0.138 -0.472 -0.953 -1.006 -1.111 -0.912 -0.416 -0.311 -0.355 -0.305
1949  0.015  0.045  0.247  0.551  0.434 -0.133 -0.235 -0.462 -0.501 -0.090  0.117  0.281
1950  0.622  0.444  0.381  0.308  0.121  0.211  0.291  0.313  0.561  0.688  0.993  1.242
1951  1.320  1.467  1.596  1.462  1.619  1.628  1.522  1.492  1.254  0.797  0.490  0.295
1952  0.169 -0.292 -0.364 -0.367 -0.565 -0.716 -0.700 -0.703 -0.708 -0.452 -0.568 -0.170
1953 -0.031  0.147  0.322  0.544  0.425  0.531  0.409  0.196  0.122  0.128 -0.429 -0.542
1954 -0.659 -1.254 -1.793 -1.707 -1.843 -1.804 -1.342 -0.984 -0.609 -0.465 -0.190  0.081
1955  0.317  0.490  0.617  0.357  0.396  0.315  0.041  0.146  0.342  0.407  0.542  0.836
1956  1.086  1.116  0.975  0.991  0.979  0.719  0.700  0.759  0.654  0.336 -0.039 -0.112
1957  0.088  0.257  0.647  1.406  1.729  1.616  1.605  1.415  0.985  0.633  0.141 -0.270
1958 -0.642 -0.527 -0.571 -0.265 -0.013 -0.051 -0.240 -0.256 -0.349 -0.604 -0.510 -0.603
1959 -0.468 -0.320 -0.127  0.106  0.096 -0.244 -0.386 -0.383 -0.310 -0.112  0.181  0.360
1960  0.434  0.093 -0.056 -0.265 -0.519 -0.600 -0.406 -0.489 -0.486 -0.511 -0.360 -0.081
1961  0.145  0.325  0.469  0.228 -0.237 -0.396 -0.584 -0.490 -0.312  0.059  0.369  0.618
1962  0.332 -0.101 -0.279 -0.705 -0.993 -0.847 -0.491 -0.607 -0.537 -0.484 -0.327 -0.311
1963 -0.130 -0.109  0.065  0.011 -0.090 -0.242 -0.165 -0.360 -0.623 -0.722 -0.933 -1.279
1964 -1.351 -1.315 -1.555 -1.435 -1.187 -1.000 -0.530  0.015  0.470  0.779  0.910  0.878
1965  1.119  1.391  1.837  2.174  2.209  2.021  1.487  0.759  0.213 -0.107 -0.337 -0.562
1966 -1.130 -1.489 -1.814 -2.186 -2.372 -2.019 -1.877 -1.708 -1.417 -1.187 -0.782 -0.231
1967 -0.080 -0.022 -0.138 -0.458 -0.969 -1.254 -1.450 -1.545 -1.675 -1.725 -1.618 -1.541
1968 -1.330 -1.167 -1.102 -1.242 -1.198 -1.070 -0.689 -0.530 -0.435 -0.392 -0.780 -1.503
1969 -1.510 -1.157 -0.714  0.048  0.616  0.487  0.188 -0.102 -0.462 -0.499 -0.302 -0.350
1970 -0.776 -1.029 -1.392 -1.732 -2.005 -1.878 -1.737 -1.297 -0.965 -0.281  0.226  0.450
1971  0.564  0.860  0.692  0.402  0.400  0.214  0.100  0.096  0.144  0.084  0.217  0.253
1972  0.439  0.567  0.656  0.849  1.134  1.522  1.661  1.643  1.484  1.188  0.599  0.121
1973 -0.298 -0.683 -1.119 -1.232 -1.132 -0.869 -0.574 -0.049  0.496  1.149  1.720  1.976
1974  2.153  2.136  1.971  1.741  1.716  1.513  1.240  0.899  0.831  0.639  0.481  0.360
1975  0.596  0.744  0.853  0.946  1.334  1.458  1.498  1.728  1.927  1.980  1.944  1.908
1976  1.725  1.727  1.696  1.812  2.058  2.357  2.214  1.889  1.360  0.815  0.308  0.072
1977 -0.159 -0.260 -0.438 -0.651 -0.904 -1.183 -1.524 -1.729 -1.943 -2.102 -1.909 -1.633
1978 -1.568 -1.281 -0.999 -0.982 -0.906 -0.787 -0.735 -0.617 -0.350 -0.083  0.026 -0.184
1979 -0.338 -0.303 -0.342 -0.183  0.072  0.340  0.450  0.472  0.312  0.017 -0.278 -0.753
1980 -1.071 -1.201 -1.041 -0.998 -1.040 -1.040 -1.018 -1.136 -1.283 -1.291 -1.390 -1.423
1981 -1.348 -1.093 -0.831 -0.554 -0.492 -0.462 -0.534 -0.607 -0.680 -0.575 -0.543 -0.607
1982 -0.926 -1.298 -1.723 -2.177 -2.203 -1.795 -1.337 -0.791  0.225  1.041  1.560  1.802
1983  1.977  2.170  2.502  3.135  4.016  4.553  4.424  4.069  3.314  2.526  1.830  1.431
1984  1.109  0.968  0.662  0.425  0.218 -0.101 -0.432 -0.457 -0.188  0.258  0.286  0.334
1985  0.410  0.168 -0.497 -0.645 -0.850 -1.297 -1.531 -1.370 -1.479 -1.475 -1.115 -0.760
1986 -0.742 -0.631 -0.579 -0.947 -1.370 -1.476 -1.672 -1.797 -1.754 -1.686 -1.690 -1.410
1987 -1.088 -0.642 -0.282 -0.236 -0.325 -0.623 -1.042 -1.212 -1.331 -1.401 -1.484 -1.515
1988 -1.647 -1.534 -1.429 -1.360 -1.228 -1.139 -0.994 -0.652  0.127  0.807  1.548  2.359
1989  2.704  2.613  2.092  1.480  0.710  0.099 -0.405 -0.480 -0.487 -0.682 -0.901 -1.074
1990 -1.367 -1.620 -1.647 -1.609 -1.694 -1.758 -1.877 -2.187 -2.408 -2.411 -2.430 -2.274
1991 -1.929 -1.916 -1.794 -1.600 -1.712 -1.884 -1.849 -2.066 -2.108 -2.078 -2.009 -1.857
1992 -1.464 -0.992 -0.505 -0.368 -0.532 -0.812 -1.377 -1.801 -1.813 -1.637 -1.630 -1.271
1993 -1.064 -0.910 -0.657 -0.436 -0.697 -0.867 -1.173 -1.346 -1.468 -1.506 -1.468 -1.229
1994 -1.348 -1.493 -1.573 -1.809 -2.280 -2.770 -2.865 -2.683 -2.604 -2.340 -1.803 -1.604
1995 -1.812 -2.004 -2.283 -2.433 -2.382 -2.151 -1.651 -1.082 -0.600 -0.352 -0.143  0.060
1996  0.161 -0.228 -0.413 -0.753 -1.371 -1.840 -1.849 -1.868 -1.767 -1.647 -1.606 -1.401
1997 -1.152 -0.981 -0.314  0.556  1.279  1.947  2.667  2.979  3.072  3.194  3.107  2.924
1998  2.737  2.864  3.038  3.009  3.212  3.272  2.824  2.508  2.422  2.316  2.279  2.516
1999  2.492  2.138  1.745  1.193  0.519 -0.029 -0.248 -0.312 -0.154  0.192  0.518  1.115
2000  1.513  1.908  1.949  1.590  0.875  0.252 -0.402 -0.995 -1.633 -9.999 -9.999 -9.999 

Update to Trans-Niño Index:

2000  1.513  1.908  1.949  1.590  0.875  0.252 -0.402 -0.656 -0.743 -0.319 -0.037  0.424

The NOAA CDC is updating the Trans-Niño Index regularly using the CAS computational recipe (above): www.cdc.noaa.gov/Pressure/Timeseries/Data/tni.long.data

Up to Contents


N3.4 (Niño 3.4 Index)

Computational Recipe:
  • Compute area averaged total SST from Niño 3.4 region.
  • Compute monthly climatology (1950-1979) for area averaged total SST from Niño 3.4 region, and subtract climatology from area averaged total SST time series to obtain anomalies.
  • Smooth the anomalies with a 5-month running mean.
  • Normalize the smoothed N3.4 by its standard deviation over the climatological period 1950-1979.
As of May 2008, this data has been updated. Please note due to computational rounding differences, numbers do not agree exactly with original data. (The original data can be accessed below.)

N34
        Jan    Feb    Mar    Apr    May    Jun    Jul    Aug    Sep    Oct    Nov    Dec
1871 -0.442 -0.470 -0.458 -0.506 -0.477 -0.470 -0.382 -0.323 -0.278 -0.312 -0.423 -0.563
1872 -0.586 -0.718 -0.676 -0.589 -0.466 -0.588 -0.646 -0.788 -0.884 -1.086 -1.068 -1.097
1873 -1.177 -1.140 -0.989 -0.867 -0.707 -0.464 -0.356 -0.472 -0.577 -0.653 -0.810 -1.048
1874 -1.205 -1.252 -1.247 -1.154 -1.103 -1.021 -1.062 -1.218 -1.409 -1.488 -1.390 -1.203
1875 -0.993 -0.862 -0.797 -0.781 -0.884 -0.967 -0.964 -0.937 -0.921 -0.934 -0.974 -1.088
1876 -1.148 -1.301 -1.342 -1.163 -0.882 -0.625 -0.278  0.019  0.166  0.288  0.435  0.542
1877  0.683  0.785  0.991  1.204  1.514  1.788  2.161  2.455  2.752  3.017  3.264  3.429
1878  3.271  2.937  2.515  2.120  1.532  1.102  0.760  0.323 -0.164 -0.495 -0.621 -0.612
1879 -0.502 -0.406 -0.375 -0.377 -0.509 -0.659 -0.775 -0.851 -1.004 -1.121 -1.209 -1.214
1880 -1.102 -0.939 -0.797 -0.652 -0.557 -0.467 -0.298 -0.093  0.132  0.294  0.447  0.490
1881  0.559  0.607  0.655  0.671  0.565  0.405  0.207 -0.010 -0.267 -0.338 -0.420 -0.514
1882 -0.520 -0.320 -0.157 -0.110 -0.081 -0.043 -0.204 -0.443 -0.611 -0.705 -0.744 -0.769
1883 -0.672 -0.475 -0.312 -0.207 -0.035  0.052  0.083  0.024  0.000 -0.079 -0.104 -0.089
1884  0.054  0.194  0.403  0.427  0.547  0.586  0.580  0.501  0.605  0.581  0.556  0.548
1885  0.525  0.435  0.515  0.559  0.539  0.580  0.749  0.782  0.947  1.178  1.130  0.923
1886  0.711  0.375 -0.108 -0.382 -0.600 -0.883 -1.110 -1.244 -1.392 -1.566 -1.467 -1.444
1887 -1.429 -1.381 -1.244 -1.180 -1.008 -0.869 -0.614 -0.369 -0.215 -0.056  0.165  0.421
1888  0.597  0.673  0.819  0.923  0.929  1.059  1.154  1.379  1.877  2.156  2.458  2.685
1889  2.539  2.039  1.705  1.196  0.590  0.046 -0.336 -0.854 -1.211 -1.393 -1.823 -2.196
1890 -2.124 -2.139 -2.013 -1.516 -1.140 -1.225 -1.254 -1.379 -1.458 -1.431 -1.166 -0.899
1891 -0.531 -0.179  0.107  0.349  0.490  0.505  0.453  0.360  0.275  0.205  0.045 -0.061
1892 -0.193 -0.394 -0.553 -0.540 -0.586 -0.619 -0.726 -1.009 -1.332 -1.531 -1.705 -1.762
1893 -1.650 -1.556 -1.543 -1.499 -1.507 -1.543 -1.521 -1.583 -1.636 -1.586 -1.528 -1.518
1894 -1.406 -1.295 -1.242 -1.137 -1.031 -0.978 -1.016 -1.014 -1.059 -0.983 -0.962 -0.815
1895 -0.669 -0.452 -0.272 -0.092  0.005  0.201  0.385  0.437  0.608  0.782  0.725  0.599
1896  0.576  0.447  0.348  0.275  0.410  0.646  0.961  1.241  1.713  1.992  2.119  2.117
1897  1.982  1.488  1.045  0.642  0.369  0.153  0.161  0.001 -0.187 -0.360 -0.466 -0.592
1898 -0.632 -0.629 -0.630 -0.534 -0.517 -0.530 -0.396 -0.372 -0.497 -0.581 -0.578 -0.758
1899 -0.801 -0.710 -0.421 -0.147  0.085  0.411  0.646  0.854  1.176  1.574  1.795  2.014
1900  2.057  1.878  1.654  1.500  1.377  1.295  1.280  1.198  0.998  0.916  0.929  0.823
1901  0.740  0.665  0.492  0.215  0.080 -0.060 -0.095 -0.179 -0.238 -0.295 -0.331 -0.351
1902 -0.313 -0.142  0.147  0.542  1.067  1.473  1.842  2.059  2.261  2.205  2.237  2.060
1903  1.911  1.574  1.200  0.935  0.565  0.224 -0.037 -0.179 -0.502 -0.696 -0.816 -0.901
1904 -1.002 -0.988 -0.757 -0.471  0.008  0.391  0.614  0.943  0.927  0.914  0.952  1.124
1905  1.150  1.190  1.307  1.314  1.380  1.395  1.736  1.700  1.747  1.806  1.761  1.515
1906  1.449  1.342  1.063  0.880  0.579  0.224 -0.123 -0.423 -0.577 -0.624 -0.684 -0.597
1907 -0.448 -0.515 -0.450 -0.371 -0.377 -0.462 -0.250 -0.234 -0.210 -0.122 -0.015 -0.064
1908 -0.147 -0.231 -0.280 -0.230 -0.397 -0.350 -0.327 -0.389 -0.597 -0.788 -0.759 -0.893
1909 -0.878 -0.822 -0.541 -0.741 -0.741 -0.886 -0.921 -1.221 -1.357 -1.419 -1.407 -1.378
1910 -1.226 -1.132 -1.173 -1.171 -1.203 -1.251 -1.268 -1.181 -1.053 -1.026 -0.934 -0.761
1911 -0.703 -0.870 -0.934 -0.922 -0.781 -0.648 -0.253  0.056  0.462  0.759  1.284  1.429
1912  1.595  1.520  1.298  0.814  0.582  0.250  0.126  0.039  0.138 -0.013  0.042  0.034
1913  0.143 -0.124 -0.013  0.031 -0.026 -0.117  0.132  0.174  0.427  0.670  0.894  1.078
1914  1.188  1.158  0.971  0.826  0.783  0.936  0.947  0.971  1.016  1.020  1.006  0.967
1915  1.059  1.107  1.111  1.204  1.073  0.927  0.855  0.727  0.353  0.228  0.177 -0.075
1916 -0.273 -0.411 -0.358 -0.397 -0.506 -0.797 -0.993 -1.367 -1.776 -1.970 -1.992 -1.978
1917 -1.745 -1.332 -0.894 -0.425 -0.058  0.150  0.241  0.288  0.158 -0.076 -0.363 -0.623
1918 -0.884 -0.922 -0.711 -0.331 -0.081  0.210  0.502  0.767  0.996  1.350  1.772  1.979
1919  1.997  1.841  1.700  1.446  1.242  1.143  1.105  0.917  0.620  0.561  0.564  0.562
1920  0.700  0.759  0.655  0.588  0.490  0.356  0.494  0.644  0.516  0.429  0.513  0.258
1921 -0.264 -0.397 -0.604 -0.758 -0.655 -0.350 -0.227  0.001 -0.253 -0.358 -0.431 -0.434
1922 -0.399 -0.256  0.004  0.065 -0.006 -0.272 -0.209 -0.395 -0.379 -0.444 -0.337 -0.480
1923 -0.626 -0.693 -0.559 -0.451 -0.253  0.026  0.385  0.633  0.904  1.209  1.284  1.248
1924  1.159  0.906  0.426  0.134 -0.290 -0.648 -0.875 -0.811 -0.953 -0.903 -0.974 -0.893
1925 -0.890 -0.724 -0.596 -0.319 -0.004  0.322  0.706  1.014  1.334  1.608  1.850  1.971
1926  2.092  2.094  1.923  1.692  1.537  1.223  0.927  0.529  0.258 -0.031 -0.047  0.011
1927  0.097  0.099  0.050  0.011 -0.110 -0.106 -0.057  0.139  0.149  0.268  0.429  0.502
1928  0.378  0.329  0.299  0.123  0.105  0.075  0.115  0.042  0.049 -0.008  0.031  0.017
1929  0.034  0.039  0.053  0.163  0.215  0.267  0.410  0.524  0.522  0.667  0.736  0.731
1930  0.726  0.791  0.652  0.659  0.765  0.858  1.125  1.413  1.831  2.013  2.243  2.226
1931  2.264  2.028  1.855  1.595  1.362  1.045  0.663  0.371  0.138 -0.099 -0.262 -0.227
1932 -0.066  0.085  0.297  0.501  0.559  0.494  0.442  0.320  0.235  0.110  0.019 -0.041
1933 -0.081 -0.064 -0.011 -0.161 -0.293 -0.525 -0.735 -0.983 -1.062 -1.259 -1.258 -1.318
1934 -1.248 -1.063 -0.805 -0.600 -0.437 -0.278 -0.293 -0.271 -0.227 -0.217 -0.216 -0.153
1935 -0.135 -0.193 -0.226 -0.219 -0.313 -0.238 -0.109  0.079  0.258  0.391  0.587  0.674
1936  0.620  0.622  0.667  0.384  0.180  0.066 -0.032  0.050  0.123  0.363  0.366  0.450
1937  0.436  0.507  0.256  0.292  0.269  0.118  0.123  0.168  0.295  0.288  0.286  0.269
1938  0.307  0.272  0.167  0.005 -0.308 -0.542 -0.634 -0.802 -0.775 -0.762 -0.724 -0.947
1939 -0.950 -0.819 -0.610 -0.371  0.011  0.253  0.471  0.363  0.422  0.322  0.642  0.880
1940  1.377  1.514  1.651  1.503  1.202  1.059  0.858  0.805  0.826  1.126  1.302  1.644
1941  1.980  2.171  2.202  2.094  1.951  1.751  1.570  1.427  1.492  1.608  1.557  1.483
1942  1.297  1.124  0.781  0.490  0.215 -0.152 -0.637 -1.035 -1.337 -1.574 -1.645 -1.679
1943 -1.590 -1.330 -1.023 -0.678 -0.331 -0.020  0.100  0.027 -0.103 -0.237 -0.377 -0.296
1944 -0.204 -0.030  0.182  0.347  0.358  0.399  0.293  0.142  0.014 -0.122 -0.228 -0.305
1945 -0.442 -0.561 -0.564 -0.600 -0.603 -0.639 -0.643 -0.808 -0.778 -0.800 -0.684 -0.546
1946 -0.376 -0.391 -0.297 -0.098  0.014 -0.051  0.046  0.110 -0.003 -0.048  0.211  0.198
1947  0.304  0.338  0.228  0.166  0.126 -0.080 -0.347 -0.472 -0.717 -0.593 -0.475 -0.098
1948  0.341  0.622  0.710  0.745  0.656  0.448  0.385  0.056 -0.069  0.015 -0.110 -0.061
1949 -0.003  0.140  0.064  0.022 -0.127 -0.077 -0.304 -0.538 -0.732 -1.006 -1.218 -1.493
1950 -1.570 -1.450 -1.428 -1.344 -1.189 -1.081 -1.122 -1.035 -1.202 -1.230 -1.373 -1.300
1951 -1.260 -0.911 -0.587 -0.256  0.180  0.640  0.895  1.100  1.331  1.307  1.161  1.007
1952  0.818  0.711  0.449  0.180 -0.024 -0.177 -0.382 -0.329 -0.253 -0.280 -0.056  0.083
1953  0.180  0.495  0.804  0.852  0.875  0.801  0.786  0.670  0.620  0.566  0.668  0.507
1954  0.505  0.326  0.185 -0.127 -0.448 -0.780 -0.970 -1.129 -1.251 -1.227 -1.109 -1.068
1955 -1.010 -0.948 -1.018 -1.140 -1.257 -1.311 -1.406 -1.560 -1.782 -1.881 -1.972 -1.900
1956 -1.688 -1.364 -1.044 -0.899 -0.856 -0.840 -0.864 -0.943 -1.013 -0.949 -0.876 -0.715
1957 -0.468 -0.056  0.291  0.636  0.938  1.120  1.165  1.204  1.343  1.442  1.657  1.876
1958  1.971  1.749  1.559  1.236  0.880  0.646  0.482  0.331  0.241  0.277  0.329  0.530
1959  0.640  0.702  0.664  0.479  0.292  0.081 -0.135 -0.148 -0.123 -0.099  0.022  0.074
1960  0.043  0.097  0.179  0.146  0.180  0.184  0.207  0.125  0.054  0.087  0.045  0.014
1961  0.028  0.177  0.225  0.329  0.260  0.196  0.023 -0.228 -0.333 -0.363 -0.363 -0.290
1962 -0.178 -0.213 -0.197 -0.156 -0.161 -0.103 -0.158 -0.179 -0.261 -0.358 -0.411 -0.356
1963 -0.256 -0.147  0.047  0.206  0.524  0.781  0.999  1.192  1.351  1.401  1.356  1.297
1964  1.036  0.670  0.213 -0.222 -0.529 -0.723 -0.824 -0.948 -1.033 -1.196 -1.140 -1.005
1965 -0.789 -0.497 -0.085  0.240  0.608  1.042  1.443  1.803  2.097  2.242  2.208  2.054
1966  1.853  1.566  1.186  0.932  0.794  0.508  0.353  0.308  0.143 -0.039 -0.170 -0.348
1967 -0.445 -0.489 -0.427 -0.270 -0.104 -0.077 -0.077 -0.168 -0.247 -0.358 -0.443 -0.520
1968 -0.603 -0.641 -0.613 -0.356 -0.018  0.273  0.436  0.604  0.752  0.839  1.003  1.253
1969  1.360  1.236  1.180  1.029  0.797  0.752  0.806  0.836  0.955  1.083  1.092  1.030
1970  0.941  0.779  0.638  0.424  0.077 -0.292 -0.554 -0.791 -0.964 -1.046 -1.195 -1.369
1971 -1.530 -1.565 -1.428 -1.197 -0.976 -0.812 -0.735 -0.771 -0.812 -0.929 -0.908 -0.784
1972 -0.609 -0.302  0.101  0.490  0.826  1.254  1.549  1.915  2.244  2.592  2.676  2.614
1973  2.295  1.738  1.000  0.326 -0.276 -0.809 -1.176 -1.517 -1.885 -2.223 -2.454 -2.514
1974 -2.448 -2.139 -1.689 -1.278 -0.996 -0.694 -0.494 -0.530 -0.623 -0.725 -0.741 -0.767
1975 -0.698 -0.592 -0.579 -0.801 -1.025 -1.205 -1.435 -1.620 -1.699 -1.855 -2.041 -1.960
1976 -1.708 -1.407 -1.026 -0.477 -0.095  0.167  0.465  0.805  1.039  1.137  1.290  1.253
1977  1.145  0.820  0.681  0.576  0.582  0.523  0.735  0.948  1.122  1.264  1.396  1.385
1978  1.173  0.771  0.371  0.065 -0.181 -0.396 -0.448 -0.452 -0.385 -0.269 -0.079  0.091
1979  0.249  0.343  0.348  0.375  0.324  0.330  0.433  0.503  0.574  0.790  0.886  0.812
1980  0.772  0.731  0.624  0.602  0.550  0.440  0.362  0.245  0.149  0.202  0.134  0.008
1981  0.057 -0.018 -0.097  0.025  0.065  0.000  0.043  0.016 -0.037  0.064  0.102  0.057
1982  0.086  0.231  0.451  0.760  1.012  1.263  1.607  1.947  2.255  2.701  3.132  3.340
1983  3.277  3.006  2.713  2.226  1.592  1.051  0.603 -0.065 -0.588 -0.868 -1.063 -1.105
1984 -0.921 -0.767 -0.627 -0.623 -0.552 -0.550 -0.465 -0.567 -0.666 -1.032 -1.172 -1.363
1985 -1.375 -1.318 -1.081 -1.011 -0.887 -0.774 -0.643 -0.618 -0.545 -0.527 -0.612 -0.663
1986 -0.600 -0.592 -0.561 -0.325 -0.061  0.132  0.433  0.779  1.082  1.275  1.548  1.687
1987  1.810  1.767  1.800  1.844  1.925  1.975  2.172  2.257  2.252  2.130  1.901  1.532
1988  1.245  0.736  0.187 -0.397 -0.902 -1.417 -1.644 -1.990 -2.215 -2.386 -2.532 -2.574
1989 -2.333 -2.027 -1.635 -1.229 -0.933 -0.740 -0.516 -0.449 -0.367 -0.312 -0.139  0.043
1990  0.241  0.401  0.583  0.611  0.585  0.557  0.531  0.426  0.427  0.434  0.530  0.556
1991  0.574  0.613  0.701  0.774  0.895  0.967  0.987  1.075  1.194  1.439  1.778  2.149
1992  2.344  2.424  2.377  2.100  1.747  1.254  0.824  0.314  0.100 -0.008  0.114  0.243
1993  0.502  0.805  1.111  1.248  1.256  1.148  0.976  0.765  0.643  0.561  0.521  0.370
1994  0.272  0.200  0.239  0.341  0.467  0.617  0.737  0.908  1.136  1.398  1.563  1.670
1995  1.578  1.330  1.043  0.783  0.576  0.308  0.080 -0.182 -0.451 -0.711 -0.790 -0.847
1996 -0.752 -0.624 -0.478 -0.293 -0.110 -0.077 -0.063 -0.073 -0.146 -0.269 -0.308 -0.308
1997 -0.224 -0.038  0.388  0.875  1.437  1.992  2.511  2.868  3.214  3.373  3.511  3.474
1998  3.271  2.834  2.423  1.649  0.877  0.190 -0.290 -0.877 -1.136 -1.399 -1.599 -1.800
1999 -1.696 -1.576 -1.342 -1.143 -0.942 -0.981 -0.976 -1.069 -1.222 -1.468 -1.700 -1.929
2000 -1.969 -1.792 -1.523 -1.194 -0.884 -0.645 -0.514 -0.492 -0.508 -0.647 -0.799 -0.899
2001 -0.853 -0.724 -0.493 -0.239 -0.018  0.078  0.098  0.059 -0.012 -0.188 -0.208 -0.158
2002 -0.029  0.094  0.337  0.605  0.806  0.956  1.165  1.390  1.578  1.777  1.858  1.776
2003  1.607  1.196  0.692  0.390  0.283  0.138  0.204  0.437  0.585  0.595  0.656  0.631
2004  0.496  0.401  0.388  0.384  0.490  0.689  0.878  1.011  1.130  1.175  1.144  0.995
2005  0.892  0.797  0.730  0.665  0.625  0.511  0.422  0.248  0.037 -0.220 -0.489 -0.701
2006 -0.844 -0.802 -0.561 -0.222  0.025  0.322  0.603  0.802  1.039  1.307  1.368  1.190
2007  0.955  0.627  0.251  0.065 -0.038 -0.177 -0.416 -0.753 -1.179 -1.577 -1.858 -1.993

Up to Contents


Example Fortran 90 Code to Read Data


!>=========================================================================<

  PROGRAM READ_TNI

! Substitute N34 for TNI if you want to read the N3.4 dataset. (In this
! case make sure you have the N34.ASCII file.)

!>=========================================================================<

  IMPLICIT NONE

  CHARACTER(LEN=100)                :: TNI_FILE
                                    ! Character variable to store file name.
  INTEGER, PARAMETER                :: yr1d = 1871
                                    ! Integer parameter to store  first year
                                    ! of data.
  INTEGER, PARAMETER                :: yrnd = 2000
                                    ! Integer parameter to store  last  year
                                    ! of data.
  INTEGER, PARAMETER                :: nmpy = 12
                                    ! Integer parameter  to  store number of
                                    ! months per year.
  CHARACTER(LEN=3)                  :: DUM_CINDEX
                                    ! Character variable to store first line
                                    ! of formatted data file.
  CHARACTER(LEN=88)                 :: DUM_HEADER
                                    ! Character variable to store second line
                                    ! of formatted data file.
  INTEGER                           :: DUM_YEAR
                                    ! Integer variable  to  store first ele-
                                    ! ment of a formatted row of data.
  REAL, DIMENSION(yr1d:yrnd,1:nmpy) :: TNI
                                    ! 2D real array to store TNI data.
  INTEGER                           :: YEAR
                                    ! DO loop control variable.

!>=========================================================================<

  TNI_FILE = "TNI.ASCII"

  OPEN(UNIT=10,FILE=TRIM(TNI_FILE),ACCESS="SEQUENTIAL",FORM="FORMATTED")

  READ(10,100) DUM_CINDEX

  READ(10,200) DUM_HEADER

  DO YEAR = yr1d, yrnd

   READ(10,300) DUM_YEAR, TNI(YEAR,1:nmpy)

  END DO

  CLOSE(10)

!>=========================================================================<

  100 FORMAT( A3 )
  200 FORMAT( A88 )
  300 FORMAT( I4, 12(F7.3) )

!>=========================================================================<

  END PROGRAM READ_TNI

!>=========================================================================<

Up to Contents


Selected Figures

Fig. 1. Time series of SSTs from Niño 3.4 (N3.4 top), and TNI (bottom) from 1871 to 2000. Both time series are normalized by the standard deviation s, as given. In the top panel, shading is included to show where thesholds of ±0.4°C are exceeded, indicating ENSO events (see Trenberth, 1997). A low pass spline fit is given to highlight interdecadal variations.

 

Fig. 2. Moving cross correlations of TNI with N3.4 as 241 month running means (about 20 years). Negative lead means that TNI leads, and positive lead means N3.4 leads. Values exceeding 0.3 in magnitude are shaded.

 

Fig. 3. Correlations of SST anomalies with N3.4 for 1900-1976 and 1977-2000. Values exceeding 0.3 are hatched and less than -0.3 are stippled. The contours are ±0.1, ±0.3, ±0.5, etc.

 

Fig. 4. Correlations of SST anomalies with TNI for 1900-1976 and 1977-2000. Values exceeding 0.3 are hatched and less than -0.3 are stippled. The contours are ±0.1, ±0.3, ±0.5, etc. (The regression of SST anomalies with TNI for 1900-1976 is shown in the figure at the top of this web page.)

 

Up to Contents


References

  • Hurrell, J. W., and K. E. Trenberth, 1999: Global sea surface temperature analyses: Multiple problems and their implications for climate analysis, modeling, and reanalysis. Bull. Amer. Meteor. Soc., 80, 2661-2678.

  • Reynolds, R. W., and T. M. Smith, 1994: Improved global sea surface temperature analyses using optimum interpolation. J. Climate, 7, 929-948.

  • Trenberth, K. E., 1997: The Definition of El Niño. Bull. Amer. Meteor. Soc., 78, 2771-2777.

Up to Contents


For questions or comments, contact CAS Data Manager .

Up to Contents