Decomposition of the Brier score for weighted forecast-verification pairs

R. M.B. Young

Research output: Contribution to journalComment/debatepeer-review

13 Citations (Scopus)


The Brier score is widely used in meteorology for quantifying probability forecast quality. The score can be decomposed into terms representing different aspects of forecast quality, but this implicitly requires each forecast-verification pair to be allocated equal weight. In this note an expression is derived for the decomposed Brier score that accounts for weighted forecast-verification pairs. A comparison of the unweighted and weighted cases using seasonal forecasts from the ENSEMBLES project shows that when weights are assigned proportional to the area represented by each grid point (weighting by cosine of latitude), the weighted forecasts give improved Brier and reliability scores comparedwith the unweighted case. This result is consistent with what is expected, given that tropical predictability is generally better than extratropical predictability.

Original languageEnglish
Pages (from-to)1364-1370
Number of pages7
JournalQuarterly Journal of the Royal Meteorological Society
Issue number650
Publication statusPublished - Jul 2010
Externally publishedYes


  • Forecast reliability
  • Forecast resolution
  • Numerical weather prediction
  • Observational uncertainty
  • Probability forecasting
  • Seasonal forecasting

ASJC Scopus subject areas

  • Atmospheric Science


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