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Anomaly Correlation Coefficient
ECMWF primary headline score for HRES
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The Anomaly Correlation Coefficient is the spacial correlation between the forecast anomaly and the verifying analysis anomaly where the anomalies are computed with respect to a model climate (M-climate, ER-M-climate, S-M-climate). Plots show the lead-time that ACC falls to a given skill threshold.
High ACC indicates good effectiveness of the model.
Current Anomaly Correlation Coefficient diagram.
Continuous ranked probability score (CRPS)
ECMWF primary headline score for medium range
The 12-month running mean percentage of continuous ranked probability score (CRPS) values for 2 m temperature exceeding 5 K at day 5 in the extratropics extra-tropics (poleward of 30° latitude), verified against SYNOP observations.
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- CRPSS = 1 the forecast has perfect skill compared to climatology;.
- CRPSS = 0 the forecast has no skill compared to climatology;.
- CRPSS = a negative value the forecast is less accurate than climatology.
Discrete Ranked Probability Skill Score (RPSS-D)
ECMWF Primary headline score for extended range
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The score is based on the evaluation of re-forecasts against SYNOP observations. Discrete Ranked Probability Skill Score (RPSS) is the deviation of the forecast values placed within a category against corresponding observations that actually lie within that category (e.g. tercile, quintile, etc.) when compared with model climate (M-climate). The words "discrete" and "ranked" refer to the discrete nature of the ranks or categories.
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- RPSS = 1 the forecast has perfect skill compared to the reference (observations, analyses or climatology) - forecast beneficial;
- RPSS = 0 the forecast has no skill compared to the reference (observations, analyses or climatology) - forecast has no benefit over climatology;
- RPSS = a negative value the forecast is less accurate than the reference (observations, analyses or climatology) - forecast misleading.
Stable equity error in probability space (1-SEEPS)
ECMWF supplementary headline score
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This score for the extra-tropics is a supplementary headline score for the ECMWF HRES.
EFI ROC skill (10m wind at day4)
ECMWF supplementary headline score
Extreme Forecast Index (EFI) is verified against analysis where an extreme event is taken as an observation exceeding 95th percentile of station climate.
Current EFI ROC skill diagram.
Fraction of large CRPS (2m temperature)
ECMWF complementary headline score
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The CRPS for the forecast temperature is calculated comparing the Cumulative Distribution Functions (CDF) for the forecast temperature against observations (or analyses) of temperature over a given period and here has the dimensions of temperature.