PROGRAMME

International Workshop on
Tropical Cyclone
Ocean Interaction

In the Northwest Pacific

19-21 June 2019
Hotel Seogwipo Kal, Jeju, Korea

Abstract Submission

[Oceanic and Atmosphere-Ocean Interaction Processes] Effects of ocean surface waves on tropical cyclone – ocean interaction

Tetsu Hara 2019.05.31 05:26

Presentation Type* (Oral/Poster) :Oral

Author(Affiliation) :

Tetsu Hara, Isaac Ginis, Xuanyu Chen, Xiaohui Zhou

Graduate School of Oceanography, University of Rhode Island, USA

Brandon Reichl

Princeton University and Geophysical Fluid Dynamics Laboratory, USA

 

Ocean surface waves affect the tropical cyclone (TC) – ocean interactions in a variety of ways. In particular, (1) surface waves (sea states) modify the exchange of momentum, heat, and moisture at the air-sea interface under TCs, (2) surface waves modify the upper ocean turbulence (Langmuir turbulence), deepening of the ocean mixed layer, and the sea surface temperature cooling under TCs, and (3) surface waves modify the upper ocean currents by modifying the effective wind forcing (when waves are growing or decaying) and by applying additional forces (e.g., Coriolis-Stokes, Stokes-vortex, Stokes-shear). In this presentation we focus on the first two effects.

 

Our modeling results in deep water predict enhanced sea state dependence of the drag coefficient for a fast moving TC than for a slow moving storm or for simple fetch-dependent seas. This may be attributed to swell that is significantly misaligned with local wind. The sea state dependence is further enhanced in finite to shallow waters. In particular, the drag coefficient may increase by as much as 30-40% in shallow water under a landfalling storm.

 

Our modeling study shows that the sea-state-dependent Langmuir turbulence parameterization significantly modifies the three-dimensional ocean response to a TC. This is due to the reduction of upwelling and horizontal advection where the near-surface currents are

reduced by Langmuir turbulence. The scheme without the sea state dependence not only misses the impact of sea-state dependence on the surface cooling, but it also misrepresents the impact of the Langmuir turbulence on the Eulerian advection.

 

These studies suggest that explicitly resolving the sea-state-dependence of the drag coefficient and the Langmuir turbulence will lead to increased accuracy in predicting the ocean response in coupled tropical cyclone–ocean models.