Satellite-driven observational and numerical modeling evidence of negative surge by typhoon Talim 2017 over the Shelf of the East China Sea

Abstract

The typhoon Talim was generated in the Northwest Pacific (NWP), propagating northwest in the NWP, entering into the East China Sea off the northeastern Taiwan, and keeps propagating northeastwardly before crossing the Kyushu, Japan, from Sep.9 to 17, 2017. Its intensity in the East China Sea (ECS) increases from category 2 to category 4, and it rapidly weakens to category 1, after its eastward turning on the shelf of the East China Sea. The satellite altimeter data revealed the particularly dominant feature of surge in the ECS, while the surge pattern is not clearly shown in the open ocean of the NWP, south of the Ryukyu Islands, due to the superposition of the surge and the sea surface disturbance from the dominant eddy features by existence of warm and cold eddies in the NWP. Meanwhile the clear negative feature newly appears to exist in the ECS off the northeast Taiwan. The broad negative surge didn’t exist several days before typhoon Talim approaches toward the ECS, suggesting that the negative surge is driven by Talim. Such a clear generation over the broad region has never been reported with observational evidence. In order to see the generation process in the area the numerical modelling was carried out to simulate the surge pattern during the propagation of typhoon Talim using the surge model of the NWP (Kang et al., 2017). The model results reveal the intensive generation of the negative surge when p.9 to 17, 2017. Its intensity in the East China Sea (ECS) increases from category 2 to category 4, and it rapidly weakens to category 1, after its eastward turning on the shelf of the East China Sea. The satellite altimeter data revealed the particularly dominant feature of surge in the ECS, while the surge pattern is not clearly shown in the open ocean of the NWP, south of the Ryukyu Islands, due to the superposition of the surge and the sea surface disturbance from the dominant eddy features by existence of warm and cold eddies in the NWP. Meanwhile the clear negative feature newly appears to exist in the ECS off the northeast Taiwan. The broad negative surge didn’t exist several days before typhoon Talim approaches toward the ECS, suggesting that the negative surge is driven by Talim. Such a clear generation over the broad region has never been reported with observational evidence. In order to see the generation process in the area the numerical modelling was carried out to simulate the surge pattern during the propagation of typhoon Talim using the surge model of the NWP (Kang et al., 2017). The model results reveal the intensive generation of the negative surge when