Towards developing an operational Indian ocean dipole warning system for Southeast Asia

Area of Science:

• Climatology and Meteorology
• Oceanography
• Disaster Risk Reduction

Background:

• Strong positive Indian Ocean Dipole (IOD) events in 2019 and 2023 caused significant disasters in Southeast Asia.
• Existing criteria for IOD monitoring and prediction require refinement to improve early warning capabilities.

Purpose of the Study:

• To evaluate current Indian Ocean Dipole (IOD) monitoring and prediction criteria.
• To develop an improved IOD warning system tailored for Southeast Asia.
• To assess the impact of methodological choices on IOD event identification and prediction accuracy.

Main Methods:

• Analysis of subjective choices in IOD event identification, including observational datasets, baseline periods, and time averaging.
• Evaluation of the Dipole Mode Index (DMI) sensitivity to different sea-surface temperature datasets and averaging periods.
• Assessment of climate model skill in capturing IOD strength and phase, identifying prediction errors.

Main Results:

• Methodological choices significantly impact DMI calculations and IOD state assessments.
• The southern Maritime Continent experiences IOD rainfall impacts even below operational thresholds, indicating a need for impact-based criteria.
• Models generally capture the active IOD phase but often overestimate its strength, necessitating calibration.

Conclusions:

• Current IOD monitoring methods show variability; an objective standard operating procedure is proposed for timely alerts.
• Calibration of DMI-based products is recommended for more accurate IOD predictions.
• An impact-based threshold for IOD events is suggested to better capture regional climate impacts.