Interactions of tropical cyclone with river plumes

Ocean supplies energy, i.e., surface heat flux, to tropical cyclones (TCs), which is fundamental to their development, maintenance and intensification; ocean, in turn, can give a negative feedback to the TC intensity by the sea surface cooling, which is induced by the mixing and upwelling processes near the storm core. The strength of the surface cooling depends on upper ocean thermal structures as well as the storm translation speed (STP) and wind speed (WS). During a TC event, another important factor controlling the surface cooling is the upper ocean stratification, which is determined by the vertical density gradient and prevents the cooling of the mixed layer by underlying waters. Although the density is determined by both sea temperature and salinity, the vertical gradient is mainly controlled by temperature over most of the world ocean due to relatively homogenous vertical salinity profile. However, fresh surface water may induce a marked halocline (high vertical gradient of salt), producing a strong pycnocline and preventing the mixing process. In particular, for TCs passing over river plumes where a great density gradient is induced, this effect may be critical since the TCs are very sensitive to variations of the surface cooling due to the mixing. This study investigates the impact of river plumes on tropical cyclone intensity, particularly focusing on the variation of the sea surface cooling by the salinity's effect, as well as the response of river plumes to TCs.