Consistent impacts of surface enthalpy and drag coefficient uncertainty between an analytical model and simulated tropical cyclone maximum intensity and storm structure

Several previous studies have demonstrated the significant sensitivity of simulated tropical cyclone structure and intensity to variations in surface-exchange coefficients for enthalpy (C_k) and momentum (C_d), respectively. In this study we investigate the consistency of the estimated peak intensity, intensification rate, and steady-state structure between an analytical model and idealized axisymmetric numerical simulations for both constant C_k and C_d values and various wind speed–dependent representations of C_k and C_d. The present analysis with constant C_k and C_d values demonstrates that the maximum wind speed is similar for identical C_k/C_d values less than 1, regardless of whether changes were made to C_k or C_d. However, for a given C_k/C_d greater than 1, the simulated and theoretical maximum wind speed are both greater if C_d is decreased compared to C_k increased. This behavior results because of a smaller enthalpy disequilibrium at the radius of maximum winds for larger C_k. Additionally, the intensification rate is shown to increase with C_k and C_d and the steady-state normalized wind speed beyond the radius of maximum winds is shown to increase with increasing C_d.