Effects of surface exchange coefficients for high wind speeds on intensity and structure of tropical cyclones: Numerical simulations for typhoon IOKE(2006)

Numerical simulations for Typhoon Ioke (2006) are carried out by using the WRF model and that with the revised formulation of exchange coefficients for momentum (C_d) and enthalpy (C_k), in order to examine the influences of surface exchange coefficients in strong winds upon the structure and intensity of tropical cyclones. The simulated results show that the reduced exchange coefficients in strong winds do not significantly affect the minimum surface pressure of the tropical cyclone while the maximum wind speed at the surface increases significantly. Furthermore, it is found that the convective intensity is significantly decreased in the reduced-C_d case specifically in the eyewall region. It is also shown that in spite of the reduced drag coefficient at high wind speed, the surface convergence does not change.