Dynamical tropopause based on isentropic potential vorticity gradients

Conceptually, significant isentropic gradients shown on the middle world PV maps reflect the underlying transport barrier associated with the tropopause, formed by jet streams that separate tropospheric air masses at low latitudes and stratospheric air masses at high latitudes. Largely owing to the lack of a general method, the dynamical tropopause has often been represented by a PV value chosen ad hoc without any temporal or spatial differentiation.

In this work, we present a method for determining the PV isoline of the dynamical tropopause based on the isentropic PV gradients. Using 1 year of data from the European Centre for Medium–Range Weather Forecasts, the spatial and temporal variability of this PV gradient-based dynamical tropopause is examined. The results show that in general there is a broad distribution of PV values at the dynamical tropopause, ranging from 1.5 to 5 potential vorticity units.