Upper‐level trajectories in the prototype problem for tropical cyclone intensification

Abstract

Data from an idealized three-dimensional numerical simulation of tropical cyclone intensification are used to calculate Lagrangian air parcel trajectories emanating from the inflow layer that develops beneath the upper-tropospheric outflow layer. It is found that about half of these trajectories end up in the outflow layer itself. The other half slowly subside to the mid-to upper troposphere, below the outflow layer, and drift slowly outwards as a result of a relatively weak overturning circulation in that region. Calculations show that pseudo-equivalent potential temperature is not approximately conserved along the air parcel trajectories, indicating that the turbulent diffusion of heat and moisture and/or the latent heat changes by freezing or melting along the trajectories is appreciable in the mid-and upper troposphere.

Tropical cyclone life cycle in a three‐dimensional numerical simulation

“…There are prominent layers of inflow sandwiching the upper-tropospheric outflow layer, the strongest one beneath the outflow in the height range of about 9-12 km has a maximum inflow of 3.3 m⋅s −1 at a height of 10.3 km. These inflow layers have been the subject of recent investigations by Montgomery et al (2020), Wang et al (2020) and Wang and Smith (2021).…”