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The Interaction of Supertyphoon Maemi (2003) With a Warm Ocean Eddy
[[abstract]]Understanding the interaction of ocean eddies with tropical cyclones is critical for improving the understanding
and prediction of the tropical cyclone intensity change. Here an investigation is presented of the
interaction between Supertyphoon Maemi, the most intense tropical cyclone in 2003, and a warm ocean
eddy in the western North Pacific. In September 2003, Maemi passed directly over a prominent (700 km
500 km) warm ocean eddy when passing over the 22°N eddy-rich zone in the northwest Pacific Ocean.
Analyses of satellite altimetry and the best-track data from the Joint Typhoon Warning Center show that
during the 36 h of the Maemi–eddy encounter, Maemi’s intensity (in 1-min sustained wind) shot up from 41
m s 1 to its peak of 77 m s 1. Maemi subsequently devastated the southern Korean peninsula. Based on
results from the Coupled Hurricane Intensity Prediction System and satellite microwave sea surface temperature
observations, it is suggested that the warm eddies act as an effective insulator between typhoons
and the deeper ocean cold water. The typhoon’s self-induced sea surface temperature cooling is suppressed
owing to the presence of the thicker upper-ocean mixed layer in the warm eddy, which prevents the deeper
cold water from being entrained into the upper-ocean mixed layer. As simulated using the Coupled Hurricane
Intensity Prediction System, the incorporation of the eddy information yields an evident improvement
on Maemi’s intensity evolution, with its peak intensity increased by one category and maintained at
category-5 strength for a longer period (36 h) of time. Without the presence of the warm ocean eddy, the
intensification is less rapid. This study can serve as a starting point in the largely speculative and unexplored
field of typhoon–warm ocean eddy interaction in the western North Pacific. Given the abundance of ocean
eddies and intense typhoons in the western North Pacific, these results highlight the importance of a
systematic and in-depth investigation of the interaction between typhoons and western North Pacific eddies.
Mesoscale eddies in the northern South China Sea
[[abstract]]A fine-grid resolution model with realistic bathymetry and forcing has been developed to study the characteristics of the mesoscale eddies for the northern South China Sea (SCS). The SCS model derives its open-boundary conditions from a larger-scale model, which minimizes errors related to the uncertainty of the Kuroshio intrusion at the open boundaries. The model results are consistent with previous observations. Model sea-surface height anomaly demonstrates that the hydrography and circulation in the northern SCS are modulated by westward-propagating mesoscale eddies originating in the vicinity of the Luzon Strait. This explains the observed intra-seasonal fluctuations at the SouthEast Asian Time-series Study (SEATS) station. The mesoscale eddies have the same propagation speed as baroclinic Rossby waves (∼0.1 ms?1). The periods of eddy shedding estimated from Strouhal number are around 40–50 days in December and 80–120 days in August, respectively. The seasonal variability of the Kuroshio intrusion results in more eddies in winter than in summer.