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Last updated:
Singular spectrum analysis (SSA: Vautard and Ghil 1989) and the maximum entropy method (MEM: Penland et al.1991) are combined to produce long-lead forecasts of sea-surface temperature (SST) anomalies averaged over the Nino-34 area. The forecast is for up to one year ahead based on data from January 1950 through May 2012.
Detailed information on the forecast method can be found in Keppenne and Ghil (1992) and in the March 1995 issue of of the Center for Ocean-Land-Atmosphere Studies's Experimental Long-Lead Forecast Bulletin (ELLFB) (also Jiang et al. 1995). Briefly, the time series is filtered by SSA so that only the statistically significant low-frequency components are retained, specifically the quasi-quadrennial (QQ) and the quasi-biennial (QB) components of ENSO variability (Rasmusson et al. 1990; Keppenne and Ghil 1992; Jiang et al. 1995). Next, MEM is applied to advance these components in time. The extended components are then used in the SSA-reconstruction to produce the forecast values.
The current SSA-MEM forecast for Nino-34 SST anomalies (Fig. 1) is for a near-neutral conditions through 2012.
Fig. 1. Forecast Nino-34 SSTAs for the next 12 months using the SSA-MEM scheme. The red line is Nino-34 SSTAs, data-adaptively filtered by SSA, and it's prediction; the solid blue line is raw SST data.
Ghil, M., and N. Jiang, 1998: Recent forecast skill for the El Nino/Southern
Oscillation. Geophys. Res. Lett.,25, 171-174.
Ghil, M., M. R. Allen, M. D. Dettinger, K. Ide, D. Kondrashov, M. E. Mann,
A. W. Robertson, A. Saunders, Y. Tian, F. Varadi, and P. Yiou, 2002:
Advanced spectral methods for climatic time series, Rev. Geophys.,
40(1), pp. 3.1-3.41, 10.1029/2000RG000092.
Jiang, N., D. Neelin and M. Ghil, 1995: Quasi-quadrennial and quasi-biennial
variability in the equatorial Pacific. Clim. Dyn., 12, 101-112.
Keppenne, C.L. and M. Ghil, 1992: Adaptive filtering and prediction of the
Southern Oscillation Index. J. Geophys. Res, 97,20449-20454.
Penland, C., M. Ghil and K. M. Weickmann, 1991: Adaptive filtering and
maximum entropy spectra, with application to changes in atmospheric angular
momentum. J. Geophys. Res., 96, 22, 659-22, 671.
Vautard, R., and M. Ghil, 1989: Singular spectrum analysis in nonlinear
dynamics with applications to paleoclimatic time series. Physica D, 35,
395-424.
