Summer Predictability Barrier of Indian Ocean Dipole Events and Corresponding Error Growth Dynamics

Abstract

AbstractThe effects of sea temperature errors in both tropical Pacific and Indian oceans on the predictability of positive Indian Ocean dipole (IOD) events are explored by using the GFDL CM2p1 coupled model. The results show that the positive IOD events tend to occur with a “winter predictability barrier” (WPB) and a “summer predictability barrier” (SPB). More is known about the WPB, while less is known about the SPB. This study focuses on the SPB. The results demonstrate that two types of initial errors are more likely to cause a significant SPB. One type is of large and negative sea surface temperature anomalies (SSTAs) in the central‐eastern Pacific and a dipole mode‐structured subsurface sea temperature that has negative anomalies in the upper layers of the eastern equatorial Pacific and positive anomalies in the lower layers of the western equatorial Pacific; the other type shows a pattern almost opposite of the former type. By tracking evolutions of both types of initial errors, it is found that their Pacific Ocean (PO) component‐induced northwesterly wind in the east pole of IOD is significantly suppressed by the summer strongest climatological southeasterly and positive IOD‐induced southeasterly wind there, finally causing the considerable suppression of the loss of latent heat flux in the east pole and then favors the fastest growth of a positive SST error in this region during summer. Then a significant SPB for the IOD occurs.