Why Do the Maximum Intensities in Modeled Tropical Cyclones Vary Under the Same Environmental Conditions?

In this study w e explored why the different initial tropical cyclone structures can result in different steady-state maximum intensities in model simulations with the same environmental conditions. We discovered a linear relationsh ip between the radius of maximum wind (r_m) and the absolute angular momentum that passes through r_m (M_m) in the model simulated steady-state tropical cyclones that r_m = aM_m+b. This nonnegligible intercept b is found to be the key to making a steady-state storm with a larger M_m more intense. The sensitivity experiments show that this nonzero b results mainly from horizontal turbulent mixing and decreases with decreased horizontal mixing. Using this linear relationship from the simulations, it is also found that the degree of supergradient wind is a function of M_m as well as the turbulent mixing length such that both a larger M_m and/or a reduced turbulent mixing length result in larger supergradient winds.