Storm Size Modulates Tropical Cyclone Intensification through an Oceanic Pathway in Global Oceans

Typical tropical cyclone (TC) attributes, including translation speed and intensity, have been demonstrated to affect TC intensification via modulating sea surface temperature (SST) cooling effect underneath TCs, while the effect of storm size is relatively less explored. Using satellite-observed SST during 2004-21, we examine the effect of storm size on TC-induced SST anomalies (SSTAs) and TC intensification in global TC-active oceans (including the western North Pacific, eastern North Pacific, North Atlantic, southern Indian Ocean, and southern Pacific) and compare their interbasin differences. In all basins, SSTAs have the strongest correlation with 34-kt (1 kt 0.51 m s21) wind radius (R34), which is thus utilized as the representative storm size among various TC wind radii. Globally, large TCs induce stronger and more widespread SSTAs, which reduce ocean's enthalpy flux supply and thus suppress TC intensification, as compared to small TCs. This modulating effect emerges in each basin, suggesting a globally consistent effect of storm size on TC intensifica- tion 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. Storm size varies greatly across global basins, and thus its effect on TC intensification through this oceanic pathway exhibits considerable interbasin differences. The interbasin difference in storm size partly contributes to the interbasin difference in SSTA under same TC intensity. Our results suggest that accurately representing storm size in TC coupled models can potentially improve cooling estimation and TC intensity prediction. SIGNIFICANCE STATEMENT: Storm size is an important parameter which characterizes tropical cyclone (TC) wind structure. Existing studies report that storm size influences TC intensification from an atmospheric perspective via modulating vortex dynamics. By examining global TCs, here we propose an explanation from the oceanic perspective: large TCs tend to induce stronger SST cooling, reducing enthalpy supply and suppressing TC intensification compared to small TCs. Consequently, small TCs are more likely to undergo rapid intensification}an extremely TC-intensifying event. Despite interbasin differences, the modulating effect of storm size via this oceanic pathway is universal over global TC-active basins. Therefore, precisely characterizing storm size and this oceanic pathway are essential for evaluating ocean's energy to TCs and forecasting rapid intensification event and TC intensity.