Main drivers of Indian Ocean dipole asymmetry revealed by a simple IOD model
- 1Irreversible Climate Change Research Center, Yonsei University, Seodaemun-gu, Seoul, 03722, Republic of Korea
- 2Department of Atmospheric Sciences, Yonsei University, Seodaemun-gu, Seoul, 03722, Republic of Korea
- 3Division of Environmental Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Republic of Korea
- 4CSIRO Environment, Aspendale, Victoria 3195, Australia
- 5Australian Research Council (ARC) Centre of Excellence for Climate Extremes, and Climate Change Research Centre, The University of New South Wales, Sydney 2052, Australia
- 6Department of Atmospheric Sciences, University of Washington at Seattle, U.S.A.
- 7Institute for Convergence Research and Education in Advanced Technology, Yonsei University, Seoul, 03722, Republic of Korea
Indian Ocean Dipole phenomenon (IOD) refers to a dominant zonal contrast pattern of sea surface temperature anomaly (SSTA) over tropical Indian Ocean (TIO) on interannual time scales. Its positive phase, characterized by anomalously warm western TIO and anomalously cold southeastern TIO, is usually stronger than its negative phase, namely a positively skewed IOD. Here, we investigate causes for the IOD asymmetry using a prototype IOD model, of which physical processes include both linear and nonlinear feedback processes, El Nino’s asymmetric impact, and a state-dependent noise. Parameters for the model were empirically obtained using various reanalysis SST data sets. The results reveal that the leading cause of IOD asymmetry without accounting seasonality is a local nonlinear process, and secondly the state-dependent noise, the direct effect by the positively skewed ENSO and its nonlinear teleconnection; the latter two have almost equal contribution. However, the contributions by each process are season dependent. For boreal summer, both local nonlinear feedback process and the state-dependent noise are major drivers of IOD asymmetry with negligible contribution from ENSO. The ENSO impacts become important in boreal fall, along with the other two processes.
This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (NRF-2018R1A5A1024958)
How to cite: Park, H.-J., An, S.-I., Kim, S.-K., Cai, W., Santoso, A., Kim, D., and Kug, J.-S.: Main drivers of Indian Ocean dipole asymmetry revealed by a simple IOD model, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-2165, https://doi.org/10.5194/egusphere-egu23-2165, 2023.
