Self-stratification of tropical cyclone outflow. Part I: Implications for storm structure

These isentropic surfaces generally lie just above the tropopause, where the vertical temperature structure is approximately isothermal, so it has been assumed that the absolute temperature of the outflow is nearly constant.

Here we show that this assumption is not justified, at least when applied to storms simulated by a convection-resolving axisymmetric numerical model, in which much of the outflow occurs below the ambient tropopause and develops its own stratification, unrelated to that of the unperturbed environment. We here propose that this stratification is set in the storm's core by the requirement that the Richardson Number remain near its critical value for the onset of small-scale turbulence.