Python-Based Supercell Tracking for Coarse Temporal and Spatial Resolution Numerical Model Simulations

• Published in: Journal of atmospheric and oceanic technology Vol. 38; no. 9; p. 1551
• Main Authors: Gropp, Matthew E., Davenport, Casey E.
• Format: Journal Article
• Language: English
• Published: Boston American Meteorological Society 01.09.2021
• Subjects: Algorithms; Atmospheric data; Climate; Climate models; Climatology; Datasets; Helicity; Mathematical models; Mean winds; Methodology; Methods; Modelling; Nowcasting; Numerical models; Numerical simulations; Python; Regional climate models; Regional climates; Resolution; Spatial discrimination; Spatial resolution; Supercell thunderstorms; Supercells; Temporal resolution; Thunderstorms; Tracking; Updraft
• ISSN: 0739-0572; 1520-0426; 1520-0426
• DOI: 10.1175/JTECH-D-20-0122.1

Deep convective thunderstorm tracking methodologies and software have become useful and necessary tools across many applications, from nowcasting to model verification. Despite many available options, many of these pre-existing methods lack a customizable, fast, and flexible methodology that can track supercell thunderstorms within convective-allowing climate datasets with coarse temporal and spatial resolution. This project serves as one option to solve this issue via an all-in-one tracking methodology, built upon several open-source Python libraries, and designed to work with various temporal resolutions, including hourly. Unique to this approach is accounting for varying data availability of different model variables, while still sufficiently and accurately tracking specific convective features; in this case, supercells were the focus. To help distinguish supercells from ordinary cells, updraft helicity and other three-dimensional atmospheric data were incorporated into the tracking algorithm to confirm its supercellular status. Deviant motion from the mean wind was also used identify supercells. The tracking algorithm was tested and performed on a dynamically-downscaled regional climate model dataset with 4 km horizontal grid spacing. Each supercell was tracked for its entire lifetime over the course of 26 years of model output, resulting in a supercell climatology over the central United States. Due to the tracking configuration and dataset used, the tracking performs most consistently for long-lived and strong supercells compared to weak and short-lived supercells. This tracking methodology allows for customizable open-source tracking of supercells in any downscaled convective-allowing dataset, even with coarse temporal resolution.