The Role of High Frequency Atmosphere-Ocean Interaction In Modulating Tropical Cyclone Activity

The interaction between Tropical Cyclones (TCs) and ocean is a major mechanism responsible for energy exchange between the atmosphere and the ocean. Very few CMIP5 models demonstrated ability in representing TCs, mainly due to their horizontal resolution. We aim to improve TCs representation in next CMIPs experiments through the new fully coupled CMCC-CM2-VHR General Circulation Model, having a horizontal resolution of ¼ degree in both atmospheric and ocean components. The model is capable to represent realistically TCs up to Cat-5 Typhoons. A good representation of the TC-Ocean interaction strongly depends on the coupling frequency between the atmospheric and the ocean components, especially when simulating fast moving TCs. In this work, we investigate the role of the coupling frequency in representing the Atmosphere-Ocean feedbacks during the TC development. A significant role of the negative Sea Surface Temperature feedback, leading to a weakening of the cyclone intensity, is found: a more realistic representation of strong TCs is obtained when coupling Atmosphere and Ocean with hourly frequency instead of daily. In addition, the positive bias (wrt IBTrACS) of the yearly averaged Power Dissipation Index is reduced by one order of magnitude (from 70% to 7%) when coupling at the hourly frequency, compared to what is obtained in forced mode or coupling Atmosphere and Ocean at the daily frequency.