Sensitivity of the Systematic Error of Extended Range Forecasts to Sea Surface Temperature Anomalies

Abstract

The sensitivity of the systematic error of extended-range forecasts to sea surface temperature (SST) anomalies is investigated. General circulation model (GCM) experiments were performed to quantify error patterns for warm, normal, and cold SST anomalies in the equatorial central Pacific. The model underestimates the strength of tropical convection during warm El Niño-Southern Oscillation (ENSO) episodes and has large zonal mean errors in midlatitudes. The model captures the negative Pacific-North American teleconnection (PNA) pattern during the cold ENSO episodes, but the simulated amplitude is too weak. The time-mean errors during warm and cold ENSO events bear little resemblance to the errors estimated from a 10-yr integration, which includes both warm and cold episodes. The time-mean error of a 10-yr integration is a good estimate of the systematic model error only for those years when SSTs are close to climatology.