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

Abstract

A new free modular 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 mimics the expected 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 among multiple overlaps. Modifications to track other physical features are possible, with each application requiring evaluation.

What caused the unseasonal extreme dust storm in Uzbekistan during November 2021?

“…In addition, we examine the role of tropopause polar vortices (TPVs) in the CAO development using the TPVTrack method [15]. TPVs are subsynopticscale, coherent tropopause-based vortices with typical radii of 100 to 1000 km and lifetimes of days to months, characterized by a local minimum of dynamic tropopause potential temperature, a cyclonic PV anomaly in the Arctic lower stratosphere, and a lowered tropopause often to the 500 hPa level or below [16][17][18].…”

Comment on wcd-2021-70

“…These objects are then tracked over time using horizontal and vertical correspondences between time steps to create unified TPV tracks, including a consideration of vortex splits and mergers. TPVTrack's efficacy as a tracking software and advantages over existing methods are verified by Szapiro and Cavallo (2018). Still, TPVTrack has noted limitations, including sensitivity to user-defined parameters and an elevated false-negative rate in temporal associations with respect to some existing methods.…”

“…To study long-lived TPVs, we utilize TPV tracks generated with the TPVTrack 1.0 software, described in depth by Szapiro and Cavallo (2018). A brief description of TPVTrack highlighting the relevant features of the package is provided here for convenience.…”

“…This information could be especially beneficial from a long-term forecasting perspective and could prove applicable to all TPVs, regardless of lifetime. Many TPVs form via splits, in which an existing TPV deforms to a point where two distinct vortices with their own closed circulations materialize (Szapiro and Cavallo, 2018). So, it is likely that a large percentage of long-track TPVs also form in this manner (note that when a vortex splits, TPVTrack associates the existing track with the one of the resulting vortices and begins a new track for the other).…”

Examining Atmospheric River Life Cycles in East Antarctica

“…TPV tracks are generated using the TPVTrack (v1.0) software, described in detail by Szapiro & Cavallo (2018) and described in its application to Southern Hemisphere TPVs in Gordon et al (2022). We briefly summarize its key aspects here for convenience.…”