The Tropical Composite Cyclones: the integrated effect of hurricanes on the ocean-­‐atmosphere coupled system

Abstract

In recent years increasing interest has been put on the role that intense Tropical Cyclones (hurricanes and typhoons) can play in modulating the climate system. Here we present a new approach to highlight strong Tropical Cyclones (TCs) fingerprint on the mean climate. Their composite effect on the surface winds is manifested through a wide cyclonic perturbation that affect a large portion of the Pacific and Atlantic tropical Oceans, as revealed by the ERA-Interim reanalysis dataset. The relationship between the resulting Tropical Composite Cyclones and the Northern hemispheric Ocean Heat Transport (OHT) is then investigated through a fully coupled atmosphere-ocean-seaice coupled global model, with high-resolution in the atmosphere (T159). The TCs activity increases significantly the poleward OHT out of the tropics, but also increases the heat transport into the deep tropics on the time scale of weeks. This effect, investigated looking at the 100 most intense Northern hemisphere TCs, is strongly correlated to the TC-induced momentum flux at the surface of the ocean: the winds associated to the TCs significantly weaken the Trade Winds in the 5-18oN latitude belt and reinforce them in the 18-30oN band. A comparison between two simulations with and without TCs effect on the wind stress over the ocean is also performed in order to better understand the role of TCs on the annually averaged OHT. The effect of the TCs induced OHT does not significantly change during the whole 1950-2069 (following 20C3M and A1B scenario) simulated period.