Intensity and timing of persistence barriers of global sea surface temperature anomalies

Due to its intrinsic connection to predictability, persistence barrier (PB) has been known as a crucial property of some important phenomena like El Niño-Southern Oscillation (ENSO), typically depicted as a rapid decline of persistence of sea surface temperature (SST) anomalies occurring at a specific season. This study reveals the PB characteristics of the global SST anomalies by extending the ENSO PB diagnosis method to quantify the PB intensity and timing. A general PB intensity index is derived, and the PB timing is newly defined as the calendar month with the highest frequency of PB occurrence. Results show that the strong PBs of global SST anomalies are mainly distributed in the regions of the tropical Pacific and southeastern tropical Indian Ocean, corresponding to the well-known PB features. The PB timing varies globally and particularly shows an evolution along the equatorial Pacific band. These results could provide additional references for oceanic predictions.