The current version of LIM SST forecasts combines SST data from the Comprehensive Ocean Atmosphere Data Set ( COADS: Woodruff et al. 1993) with data from the NCEP real time surface marine. COADS data is currently available for dates later than the year 2000. However, it is not available in real time. The SST data set prepared in a manner closest to COADS is the NCEP Surface Marine data set, which is provided by NCEP and summarized into COADS-compatible monthly statistics at PSD. The Surface Marine data set begins in 1991. Although the Surface Marine SST data set is extremely similar to COADS in the tropics, the data sets are not identical. Nevertheless, SST statistics in the two data sets are well within the uncertainties of those statistics over their common period, so we developed the LIM prediction model by training it on COADS (1951-2000) and forecast for NCEP Surface Marine (1991-2000).
Model details:
Predictions of Pacific Sea Surface Temperature Anomalies (SSTAs) are made using linear inverse modeling procedure discussed in Alexander, M. A., L. Matrosova, C. Penland, J. D. Scott, and P. Chang, 2007: Forecasting Pacific SSTs: Linear Inverse Model Predictions of the PDO. J. Climate, submitted.
Anomalies were calculated relative to 1951-2000 COADS climatology, smoothed by three months running mean procedure and projected onto the leading EOFs containing about 2/3 of the variance. Predictions of the Pacific SSTs use 15 EOFs.
The Correlation between the Truncated Time Series and the Untruncated Time Series in the Locations Shown (above the color bar). The Fraction of Variance Explained by the First 15 EOFs in Each 4 by 10 Grid Square (below the color bar) 
Description of PDO SST index predictions:
A PDO index was calculated as a time series (PC1) of EOF1 of the North Pacific SST anomalies (15N-65N Poleward). Projecting this index onto 15 EOFs calculated for SSTs in the entire Pacific ocean northward of 30S does not significantly alter the index. We apply LIM to these 15 EOFs, which include tropical variability, to develop a prediction model for the PDO. The prediction model was validated using a jackknifing procedure using six five-year verification periods in the interval between 1970 and 2000. We present the prediction (blue lines) and verification (red lines) time series corresponding to these validation periods for the PDO SST index. Gaps in the prediction time series are due to the lags incurred between verification periods in the jackknifing procedure. Correlation skill scores are between predictions and verifications as shown. Dotted lines are confidence intervals corresponding to one standard deviation of the expected prediction error.
Interpretation of SST maps:
SSTs are consolidated onto a grid 4 degrees (latitude) by 10 degrees (longitude). Values of SST and SST anomalies represent the average value within a grid box. Numerical tables of SST predictions are presented in tabular form, with a latitude-longitude pair representing the center of the grid box. Grid boxes are left blank on the map when the observational record between 1950 and 2000 at that location was considered too sparse to provide useable information in training the statistical prediction model.
Return to the main page.