Oceanic Heat Content as a Predictor of the Indian Ocean Dipole

Indian Ocean Dipole (IOD) prediction is a challenging problem, largely relying on the relationship between IOD and El Nino-Southern Oscillation (ENSO). This study demonstrates that heat content internal to the Indian Ocean can be an effective predictor providing extra IOD predictability, through constructing statistical prediction models with and without heat content as a predictor. Two recently proposed heat content predictors, equatorial heat content (EQHC) and heat content in the eastern pole of the Dipole (SEHC) are compared in this study. Results show that EQHC is more effective partly because it is relatively independent of ENSO and partly because it does not rely on IOD persistence, as does SEHC. The efficacy of EQHC as an IOD predictor is seasonally dependent, being most effective at 5-8-month lead times beginning in the preceding late boreal winter and spring. Plain Language Summary The Indian Ocean Dipole (IOD), a major climate mode in the tropical Indian Ocean, can lead to severe floods and droughts over surrounding continental areas. Prediction of the IOD is very challenging due to the apparent lack of effective predictors besides the El Nino-Southern Oscillation. This study compares two recently proposed predictors for the IOD based on upper ocean heat content, one along the equator and one in the southeastern tropical Indian Ocean. Equatorial heat content proves to be more effective, especially for predictions starting in the late boreal winter and spring. This study helps to improve our understanding of IOD dynamics and its predictability.