TC-Ocean interaction: modulating roles of ocean internal tides and storm size

Tropical Cyclones (TCs) are devastating natural disasters. Ocean thermal stratification and TC attributes (e.g., translation speed and intensity) have been demonstrated to affect TC intensification via modulating sea surface temperature (SST) cooling effect. Here, we found that both ocean internal tides and storm size could affect TC intensification. Analyzing decades of global TC data, here we explore the modulating role of ocean internal tides and storm size on TC-induced sea surface temperature anomalies (SSTA) and TC intensification in global TC-active oceans. Originating from complex interplays between astronomic tides and the SCS topography, gigantic ocean internal tides in the South China Sea (SCS) interact with TC-generated oceanic near-inertial waves and induce a strong ocean cooling effect, effectively suppressing the TC intensification. Consequently, among all global TC-active basins, the SCS stands out as a particularly difficult ocean for TCs to intensify, despite favorable atmosphere and ocean conditions. Over the SCS, TC intensification rate and its probability for a rapid intensification are only 1/2 and 1/3, respectively, of those for the rest of the world ocean. Moreover, as a typical TC attribute, storm size can also modulate TC intensification through ocean cooling effect. Large TCs induce stronger and more widespread SSTA, which reduces ocean’s enthalpy flux supply and thus suppresses TC intensification globally, as compared to small TCs. This modulating effect emerges in each basin, suggesting a globally consistent effect of storm size on TC intensification through an oceanic pathway. Small TCs, occupying weaker SST cooling and larger enthalpy flux, are more likely to undergo rapid intensification, with the probability of 1.1–1.8 times larger than large TCs in global TC-active oceans. Inclusion of this interaction between internal tides and storm size and TC in operational weather prediction systems is expected to improve forecast of TC intensity in TC-active basins.