Main drivers of Indian Ocean Dipole asymmetry revealed by a simple IOD model

Abstract Indian Ocean Dipole phenomenon (IOD) refers to a dominant zonal contrast pattern of sea surface temperature anomaly (SSTA) over tropical (TIO) on interannual time scales. Its positive phase, characterized by anomalously warm western TIO and cold southeastern TIO, is usually stronger than its negative namely positively skewed IOD. Here, we investigate causes for the IOD asymmetry using prototype model, which physical processes include both linear nonlinear feedback processes, El Nino’s asymmetric impact, state-dependent noise. Parameters model were empirically obtained various reanalysis SST data sets. The results reveal that leading cause without accounting seasonality local process, secondly noise, direct effect ENSO teleconnection; latter two have almost equal contribution. However, contributions each process are season dependent. For boreal summer, noise major drivers with negligible contribution from ENSO. impacts become important in fall, along other processes.