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The daily ensemble forecasts have been available operationnally since January 24, 1996. They were originally performed with eight members. As of August 24, 1999, eight more members were added creating a 16-member ensemble forecast system. On January 12, 2005, the Optimal Interpolation Technique for the analysis cycle was replaced with the Ensemble Kalman Filter Technique.
Each day, 16 "perturbed" 10-day weather forecasts are performed as well as an unperturbed 10-day control forecast. Of the 16 perturbed forecasts, 8 are performed with the SEF global spectral model and 8 with the GEM global model. The 16 models have different physics parametrizations, data assimilation cycles and sets of perturbed observations. Boundary conditions such as sea surface temperature, albedo and roughness length have been perturbed as well. The control forecast is initiated from the ensemble mean and produced with the SEF spectral model.
View the forecast of the normalised mean temperature anomaly for the next 10 days. The forecast starts at 00Z of the day indicated in the figure. The anomaly is with respect to the climatological mean temperature. The forecast was obtained by applying a regression equation to the ensemble mean 1000-500 hPa thickness. The contours are 0.43 multiples of the standard deviation.
Every 6 hours, we compute the standard deviation in dam of the GZ 500 hPa trial fields from the 16 representative assimilation cycles. Where the standard deviation of the trial field is large, it is important to have good observations. One might target additional observations to such areas. Another option is to manually introduce bogus observations. View.