ENSO PDO and Rainfall over Strong SST Gradients

ENSO, PDO and Rainfall over Strong SST Gradients and Ocean Currents in Minerva Hindcasts Bohua Huang Jieshun Zhu Mike Fennessy Xuelei Feng

1 -mon lead Mean SST, November 7 -mon lead

1 -mon lead SST Correlation Skill, November 7 -mon lead

1 -mon lead SST RMSE, November 7 -mon lead

Hindcast for November, 7 -mon Lead, 2000 -2011

ENSO Prediction Skill: • Based on May ICs during 1982 -2011 • SST observations: OISST More ensembles or higher resolution (AGCM)?

Jul Sep N

Jul Sep N

Prediction Skills of Nino 3. 4 index (Lead Months)

Using 5 Probability Bins • All three predictions are the same • “Overconfident”

Forecasting PDO: Can we get anything in a region of low skill (low correlation and high RMSE)? What is predictable? Looking for predictable patterns while allowing bias

Need larger ensemble size?

Rainfall over Kuroshio and Gulf Stream Does higher AGCM resolution enhance the effects of warm western boundary currents and large SST gradients ? Do we need higher OGCM resolution?

Seasonal Climate, Precipitation & SST

Seasonal Climate, Precipitation & SST

Seasonal Climate, Precipitation & SST

Seasonal Climate, Precipitation & SST

ERA 40 Athena Minerva Athena

ERA 40 Athena Minerva Athena

Minerva

Summary • SST prediction skill does not change significantly from T 319 to T 639 (T 1279). • Compared with T 319, SST RMSE is reduced for T 639 in the western equatorial Pacific. • Categorical estimate of the reliability does not change with resolution. • A PDO pattern can be predicted with skill up to 7 months (allowing for weaker strength). At same ensemble size, T 639 shows better pattern and smaller spread. Larger ensemble size may be helpful. • CGCM improves precipitation over Kuroshio near coast. Higher AGCM resolution (T 1279) enhances rainfall there, especially off the eastern coast of Japan. • AGCM produces stronger precipitation over Gulf Stream Extension and North Atlantic Current, implying stronger SST gradient forcing. • Model Kuroshio and Gulf Stream are comparable to GODAS but stay coastal too longer. Their extension flows are also weaker. High AGCM resolutions do not show a major impact.