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 speeddependent 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. Experiments with wind speed-dependent C-k and C-d were found to be generally consistent, in terms of the intensification rate and the simulated and analytical-model-estimated maximum wind speed, with the experiments with constant C-k and C-d.