Abstract:
Prediction skill for southern African (16 –
33 E, 22 –35 S) summer precipitation in the Scale Interaction
Experiment-Frontier coupled model is assessed for
the period of 1982–2008. Using three different observation
datasets, deterministic forecasts are evaluated by anomaly
correlation coefficients, whereas scores of relative operating
characteristic and relative operating level are used to
evaluate probabilistic forecasts. We have found that these
scores for December–February precipitation forecasts initialized
on October 1st are significant at 95 % confidence
level. On a local scale, the level of prediction skill in the
northwestern and central parts of southern Africa is higher
than that in northeastern South Africa. El Nin˜o/Southern
Oscillation (ENSO) provides the major source of predictability,
but the relationship with ENSO is too strong in the
model. The Benguela Nin˜o, the basin mode in the tropical
Indian Ocean, the subtropical dipole modes in the South
Atlantic and the southern Indian Oceans and ENSO Modoki
may provide additional sources of predictability.
Within the wet season from October to the following April,
the precipitation anomalies in December-February are the most predictable. This study presents promising results for
seasonal prediction of precipitation anomaly in the extratropics,
where seasonal prediction has been considered a
difficult task.
