Effects of the Cold Core Eddy on Tropical Cyclone Intensity and Structure under Idealized Air―Sea Interaction Conditions

The impacts of ocean feedback on tropical cyclones (TCs) are investigated using a coupled atmosphere–ocean model under idealized TC and cold core eddy (CCE) conditions. Results reveal negative impacts of the ocean coupling on TC development. The cold wake induced by a TC not only weakens the TC intensity but also limits the expansion of the storm circulation. The presence of CCE has boosted the TC-induced sea surface temperature cooling, which conversely inhibits the TC development. The TC appears to be weakened as it encounters the CCE edge. The intensity reduction attains a maximum shortly after the TC passes over the CCE center, and simultaneously the CCE-induced asymmetry of the storm structure is most significant as well. The TC undergoes a period of recovery after departure from the CCE, lasting about 36–48 h. During this time the residual asymmetry caused by the CCE is smoothed gradually by storm axisymmetrization. The CCE has induced smaller TC size throughout the simulation even after the TC intensity has completely recovered, an indication of longer recovery time for the TC size. Notably cooler and moister eye air in the lower troposphere, just under the warm-core height, is found in the experiment with CCE. The water vapor mixing ratio budget analysis indicates that it is primarily attributed to changes in vertical advection that occurred in the eye, that is, the undermined eye subsidence associated with the suppressed eyewall convection. The horizontal patterns of vertical motion in the boundary layer are also distinctly changed by the CCE.