Anomaly Correlation Coefficient ACC

1
Anomaly Correlation Coefficient (ACC) Purpose
Quantify the spatial correlation between forecast
and observed deviations from climatology
Definition

• Interpretation
• Measures pattern similarity, not absolute
  values
• Amplified patterns produce higher ACC skill
  scores than zonal patterns
• Limit of synoptic-scale forecast skill ACC
  0.6 (subjective)
• Source Miyakoda et al. (1972)