As the dominant ocean–atmosphere coupled phenomenon on the interannual time scale in the tropical Indian Ocean, the Indian Ocean Dipole (IOD) affects the climate and weather of nearby regions and distant areas. However, the forecasting skill for IOD events is low. How to improve such forecasts is a major challenge in climate science.

By using a coupled climate model, GFDL CM2p1 (Geophysical Fluid Dynamics Laboratory Climate Model, version 2p1), Prof. DUAN Wansuo and Dr. FENG Rong, from the Institute of Atmospheric Physics, Chinese Academy of Sciences, identified the effects of initial sea temperature errors in the tropical Indian Ocean on the predictability of IOD events and demonstrated that there is a winter predictability barrier (WPB) and a summer predictability barrier (SPB) in IOD predictions.

Furthermore, they also explored the dominant spatial patterns of the initial errors that are most likely to induce significant predictability barriers, and found that both the WPB- and SPB-related initial errors present a west–east dipole pattern, with the large values concentrated within the subsurface eastern tropical Indian Ocean. This indicates that IOD predictions are more sensitive to the initial errors over this area. Therefore, this small area is probably a sensitive area for targeted observations of IOD events. If these target observations are assimilated to the model, the IOD prediction skill could greatly improve.

"Our findings provide a new idea for data assimilation of IOD predictions as well as scientific guidance for targeted observations of IOD events." said the corresponding author DUAN.

These findings have been published in Advances of Atmospheric Sciences.

Reference

Feng, R., and W. Duan, 2019: Indian Ocean Dipole–related predictability barriers induced by initial errors in the tropical Indian Ocean in a CGCM. Adv. Atmos. Sci., 36(6), https://doi.org/10.1007/s00376-019-8224-9.

Media contact: jennylin@mail.iap.ac.cn