TPVTrack v1.0: A watershed segmentation and overlap correspondence method for tracking tropopause polar vortices

Abstract

Abstract. A new modular, free software package is described for tracking tropopause polar vortices (TPVs) natively on structured or unstructured grids. Motivated by limitations in spatial characterization and time tracking within existing approaches, TPVTrack leverages the dynamics of TPVs to represent their (1) spatial structure, with variable shapes and intensities and (2) time evolution, with mergers and splits. TPVs are segmented from the gridded flow field into spatial objects as restricted regional watershed basins on the tropopause, described by geometric metrics, associated over time by overlap similarity into major and minor correspondences, and tracked along major correspondences. Simplified segmentation and correspondence test cases illustrate some of the appeal, sensitivities, and limitations of TPVTrack, including effective representation of spatial shape and reduced false positive associations in time. Tracked TPVs in more realistic historical conditions are consistent in bulk with expectations of life cycle and mean structure. Individual tracks are less reliable when discriminating between multiple overlaps. Modifications to track other physical features are possible, with each application requiring evaluation.

A potential vorticity diagnostics package for MPAS-Atmosphere

“…These versions-collectively referred to as the original version of the PV diagnostics package-contained calculations for the 3D PV field and instantaneous tendencies from diabatic and frictional processes. Additionally, an iterative flood-fill procedure (Foley et al, 1990;Szapiro, 2019) was implemented to identify the level of the dynamic tropopause (DT; defined as the 2-PVU isosurface, where 1 PVU = 10 −6 m 2 K s −1 kg −1 ) from the diagnosed PV field, and several model variables-including θ and the diabatic and frictional PV tendencies-were interpolated onto the identified DT.…”