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| Titel |
Relative impact of model quality and ensemble deficiencies on the performance of ensemble based probabilistic forecasts evaluated through the Brier score |
| VerfasserIn |
F. Atger |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1023-5809
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| Digitales Dokument |
URL |
| Erschienen |
In: Nonlinear Processes in Geophysics ; 11, no. 3 ; Nr. 11, no. 3 (2004-09-14), S.399-409 |
| Datensatznummer |
250009245
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| Publikation (Nr.) |
 copernicus.org/npg-11-399-2004.pdf |
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| Zusammenfassung |
| The relative impact of model quality and ensemble deficiencies, on the
performance of ensemble based probabilistic forecasts, is investigated from
a set of idealized experiments. Data are generated according to a
statistical model, the validation of which is achieved by comparing
generated data to ECMWF ensemble forecasts and analyses. The performance of
probabilistic forecasts is evaluated through the reliability and resolution
terms of the Brier score. Results are as follows. (i) Resolution appears
essentially attributable to the average level of forecast skill. (ii) The
lack of reliability comes primarily from forecast bias, and to a lower
extent from the ensemble being systematically under-dispersive (or
over-dispersive). (iii) Forecast skill contributes very little to
reliability in the absence of forecast bias, and this impact is entirely due
to the finiteness of the ensemble population. (iv) In the presence of
forecast bias, reducing forecast skill leads to improve the reliability.
This unexpected feature comes from the fact that lower forecast skill leads
to a larger ensemble spread, that compensates for the strong proportion of
outliers consequent to forecast bias. (v) The lack of ensemble skill, i.e.
non systematic errors affecting both ensemble mean and ensemble spread,
contributes little, but significantly, to the lack of reliability and
resolution. |
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