A tropical cyclone is known to generate geostrophic current and near-inertial wave responses in the upper ocean. The amount of total energy imparted to the ocean and the energies of geostrophic current and wave field are dependent on parameter R - ratio of the storm spatial scale and the Rossby radius of deformation. After some adjustment period the waves leave the area of wind forcing and the geostrophic flow remains. For large R, typical for tropical cyclone conditions, most of the geostrophic energy is accumulated in the potential energy.

Observational studies conducted during the Typhoon-90 field experiment in the western Pacific clearly indicate significant elevations of the isopycnal surfaces in the ocean thermocline induces by tropical cyclones and associated changes in the potential energy. Here we use the hydrological cross-sections made before and after the passage of Typhoon Dot (9017) to a depth of 500 m to estimate the change of the potential energy induced by the storm. Knowing the near-surface wind speeds, the time of the storm impact we can estimate the total amount of energy flux from the tropical cyclone to the ocean. Assuming the continuity of the energy flux across the ocean surface and conservation of energy we can then estimate the drag coefficient. The results of these estimates will be presented and discussed.