ENSO and PDO in Two Versions of FGOALS

Abstract

The El Niño–Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) are the most climate variability at the interannual and decadal time scales, respectively. Because the typical time scale of atmospheric dynamics is usually less than one season, the ocean dynamics should play a very important role in ENSO and PDO. This study presents a detailed description of physical mechanisms responsible for ENSO and PDO in two versions of FGOALS. The positive feedback processes for ENSO and PDO are very similar, and both two negative feedback processes for ENSO and PDO are associated with Rossby propagation excited by the tropical SST anomalies. However, the westward propagating Rossby waves off-equator (5–8°N) and corresponding Sverdrup transport are related to ENSO events, while the westward propagating Rossby waves in the extra-tropics (between 15–20°N) are related to PDO events.