Mixing to Monsoons: U.S.–Indian–Sri Lankan Partnerships in Upper-Ocean Measurements for Improved Forecasts in the Bay of Bengal

Improved predictive capability of the Indian Ocean monsoons has a direct impact on the livelihood, health, and safety of more than 1 billion people in South Asia. Yet forecast skill is particularly poor at the monsoon intraseasonal timescale. Since coupled ocean-atmosphere models fail to accurately represent upper ocean conditions in the region, particularly sea surface temperature, it is likely that better understanding of ocean physics is needed to improve representation of active and break cycles of the monsoon. The Bay of Bengal has a complex upper ocean temperature and salinity structure, which is characterized by strong salinity stratification and multiple inversions in temperature. Air-sea interactions depend upon both the sea surface temperature and the vertical temperature structure, since the upper ocean heat content represents the energy readily available to drive convection in the atmosphere. To improve understanding of the circulation, upper ocean dynamics, and air-sea interactions in the Bay of Bengal, the United States, India, and Sri Lanka initiated a 5-year effort (2013–2017) that brings together major resources, scientists, and students from more than 20 research institutes and universities across the three nations. Here, I will summarize the approach and major accomplishments of this international collaborative effort.