Numerical experiments for tropical cyclone intensity to the ocean around the warm strong currents

The ocean affects tropical cyclones (TCs) through the sea surface and greatly controls intensity of TCs (e.g., central pressure, rain rate, wind speed). The intensity control by the ocean has been explained with the sea surface temperature (SST), or, the ocean heat content near the surface. The distribution of the SST or heat content varies by air sea interaction through mixing/upwelling in the upper layer in the ocean produced by TCs passing on the ocean surface, and then, cooler SST/ less heat content makes suppression of the intensity of the TCs. The suppression of the intensity is observed evident in the TCs of slow moving because of cooling in the upper ocean layer by mixing/upwelling. It is possible, however, that the intensity suppression of a TC is weakened if the TC moves slowly or stays long around the strong warm currents.

To investigate the intensity of TCs with considering the air-sea interaction around the warm strong currents, numerical experiments utilizing with atmosphere-ocean coupled model were performed; slab ocean model was for vertically one-dimensional coupled experiments and CReSS-NHOES was for three-dimensional coupled experiments. Experiments were performed for TCs which moved/stayed around the Kuroshio currents in the western North Pacific, which had warm strong horizontal flow. Sensitivity experiments employed with idealized oceanic flows were also performed to make sure the contribution of the warm strong currents to the intensity of TCs.