Influence of air–sea coupling on Indian Ocean tropical cyclones

International audienceThis paper assesses the impact of air-sea coupling on Indian Ocean Tropical Cyclones (TCs) by comparing a 20-year long simulation of a ¼° regional coupled ocean-atmosphere model with a twin experiment, where the atmospheric component is forced by sea surface temperature from the coupled simulation. The coupled simulation reproduces the observed spatio-temporal TCs distributions and TC-induced surface cooling reasonably well, but overestimates the number of TCs. Air-sea coupling does not affect the cyclogenesis spatial distribution but reduces the number of TCs by ~20% and yields a better-resolved bimodal seasonal distribution in the northern hemisphere. Coupling also affects intensity distribution, inducing a four-fold decrease in the proportion of intense TCs (stronger than Cat-1). Air-sea coupling damps TC growth through a reduction of the inner-core upward enthalpy fluxes due to the TC-induced cooling. This reduction is particularly large for the most intense TCs of the northern Indian Ocean (up to 250W.m-2), due to higher ambient surface temperatures and larger TC-induced cooling there. The negative feedback of air-sea coupling on strongest TCs is mainly associated with slow-moving storms. Sensitivity experiments using a different convective parameterization yield qualitatively similar results, with a Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporatio