Versions Compared

Old Version 2

changes.mady.by.user Bob Owens

Saved on

compared with

New Version 3

changes.mady.by.user Bob Owens

Saved on

Key

  • This line was added.
  • This line was removed.
  • Formatting was changed.

The Extreme Forecast Index (EFI is computed from the difference between Cumulative Distribution Function (CDF) curves of the M-climate and the forecast distribution of the current ensemble (ENS).  The calculations are made so that more weight is given to differences in the tails of the (climatological) distribution.

...

where Qf(Q) denotes the proportion of ENS members lying below the Q quantile of the M-climate record.  This is shown diagramatically in Fig8.1.9.2-1 where Q-Qf(Q) is represented by the blue line and the green shaded area. The term Q(1-Q) gives more weight towards the extremes of M-climate.

One can visually estimate the EFI by assessing the area between the M-climate (black) and ENS forecast (red) curves, and dividing this by what the area would be if all the ENS members predicted the M-climate extreme (i.e. a vertical line that meets the black curve at y=100%).  Whilst the answer derived by this method is only approximate it can nonetheless be a very useful aid to understanding.

...