Ratio limits · February initialization · FMAM and its months
The operational correction limits the spread ratio r = σobs/σmodel to 0.5–2. This study runs the same
screening and confirmation for that correction with wider limits (1/3–3, 1/4–4) and none, all with the same fallback (r = 1 where
the model spread is below 1 mm), to see whether the limits are worth changing. ✓ = better than the operational limits with
Holm-adjusted p < 0.05 across the 3 alternatives × 5 targets and not worse over the test years. Run at
commit fb7425f.
Confirmed better than the operational limits — published (blended) probabilities: none; rainfall amounts: none.
Probabilities
Blended tercile RPSS through the full pipeline, outer leave-one-year-out 1993–2016
| Method | Feb | Mar | Apr | May | FMAM |
|---|
| Mean-Variance Scaling (operational, 0.5–2) | +0.126 | +0.011 | +0.009 | +0.008 | +0.021 |
| MVS, ratio limits 1/3-3 | +0.126 | +0.012 | +0.010 | +0.008 | +0.021 |
| MVS, ratio limits 1/4-4 | +0.125 | +0.012 | +0.010 | +0.008 | +0.021 |
| Variance Scaling (unbounded) | +0.124 | +0.012 | +0.010 | +0.008 | +0.021 |
Amounts
Amount CRPSS, leave-one-year-out 1993–2016
| Method | Feb | Mar | Apr | May | FMAM |
|---|
| Mean-Variance Scaling (operational, 0.5–2) | +0.240 | -0.034 | -0.001 | -0.005 | -0.007 |
| MVS, ratio limits 1/3-3 | +0.245 | -0.032 | -0.000 | -0.005 | -0.007 |
| MVS, ratio limits 1/4-4 | +0.246 | -0.032 | -0.000 | -0.005 | -0.007 |
| Variance Scaling (unbounded) | +0.246 | -0.032 | -0.000 | -0.005 | -0.007 |
Where the operational limits act
Share of the corrected area, mean over the leave-one-year-out folds, 1993–2016
| Target | Lower limit active (r would be < 0.5) | Upper limit active (r would be > 2) | Spread–error, operational | Spread–error, no limits |
|---|
| Feb | 32% | 3% | 0.96 | 0.96 |
| Mar | 4% | 6% | 0.91 | 0.92 |
| Apr | 0% | 5% | 0.95 | 0.95 |
| May | 0% | 4% | 0.96 | 0.97 |
| FMAM | 0% | 3% | 0.91 | 0.92 |