Observation-Large eddy simulation comparison of ocean mixing under Typhoon Soulik (2018)

Ocean mixing by tropical cyclones (TC) can cool the sea surface and reduce heat flux from the ocean to the atmosphere ahead of the eye. This ahead of eye cooling has been shown to play a significant role in weakening as TCs translate over stratified, continental shelves. Typhoon Soulik weakened over the northern East China Sea prior to landfall at 8/2314:00 UTC on the Korean Peninsula. This weakening was attributed to cooling of the sea surface ahead of the storm. Significant sea surface cooling was corroborated through a collaborative deployment of a Slocum underwater glider with the Korean Institute of Ocean Science and Technology. This glider collected data on the state of the ocean ahead of and throughout the duration of the forcing and observed 8°C of SST cooling. The glider was flown in the vicinity of a Korean Meteorological Association surface meteorological buoy, which collected data on wind and heat flux forcing on the ocean. This study investigates the physical mechanisms driving the ocean’s response to this extreme forcing using the Price-Weller-Pinkel (PWP) one-dimensional ocean mixed layer model and an Oceananigans.jl Large Eddy Simulation (LES). An LES resolves turbulence in the flow field which allows for the study of its onset and evolution throughout the duration of the forcing. The configurations of PWP and the LES in this study are unable to capture the ocean’s response to Typhoon Soulik which implies that there are processes critical to the response that are not captured by the models.