Drag Coefficient and Its Sea State Dependence under Tropical Cyclones

Abstract The drag coefficient under tropical cyclones and its dependence on sea states are investigated by combining upper-ocean current observations [using electromagnetic autonomous profiling explorer (EM-APEX) floats deployed five cyclones] a coupled ocean–wave (Modular Ocean Model 6–WAVEWATCH III) model. estimated averaged over all storms is around 2–3 × 10 −3 for wind speeds of 25–55 m s −1 . While the weakly depends speed in this range, it shows stronger states. In particular, significantly reduced when misalignment angle between dominant wave direction exceeds about 45°, feature that underestimated models state–dependent coefficient. Since misaligned swell more common far front left-front quadrant storm (in Northern Hemisphere), also tends to be lower these areas distinct spatial distribution. Our results therefore support ongoing efforts develop implement parameterizations cyclone conditions.