SEAS5 skill of ENSO impact on Northern Benguela Coastal Upwelling Systems

Using seasonal predictions from the ECMWF SEAS-5 System, we analyze the relationship between ENSO and upwelling indices in the regions of Benguela.

We find that reanalysis show correlations between El Niño and the Southern Oscillation phenomenon (ENSO) and upwelling indices in February-March-April. The system performs a very accurate prediction in the Tropics of the Sea Surface Temperature (SST) and wind stress variables leading to a good simulation of El Niño, but to a less realistic simulation of Benguela upwelling.

The simulation of the connection between ENSO and Benguela depends on the latitude studied: Northern Benguela Eastern Boundary Upwelling System (EBUS) is more related with ENSO than Southern Benguela EBUS.

There are also changes in the predictability depending on the period of study. We focus in two periods: 1981-1998 (P1) and 1999-2016.  In SEAS-5 there is a clear relationship between Northern Benguela Upwelling System and ENSO that appears to be consistent and similar for the two periods, while in observations the relation appears to be robust only after the year 2000’s.  This result highlights the importance of taking into account the impact of changes in the background state on predictability.