Automated Temporal Tracking of Coherently Evolving Density Fronts in Numerical Models

Abstract

Oceanic density fronts can evolve, be advected, or propagate as gravity currents. Frontal evolution studies require methods to temporally track evolving density fronts. We present an automated method to temporally track these fronts from numerical model solutions. First, at all time steps contiguous density fronts are detected using an edge detection algorithm. A front event, defined as a set of sequential-in-time fronts representing a single time-evolving front, is then identified. At time step i, a front is compared to each front at time step i + 1 to determine if the two fronts are matched. An i front grid point is trackable if the minimum distance to the i + 1 front falls within a range. The i front is forward-matched to the i + 1 front when a sufficient number of grid points are trackable and the front moves onshore. A front event is obtained via forward tracking a front for multiple time steps. Within an event, the times that a grid point can be tracked is its connectivity and a pruning algorithm using a connectivity cutoff is applied to extract only the coherently evolving components. This tracking method is applied to a realistic 3-month San Diego Bight model solution yielding 81 front events with duration ≥ 7 hours, allowing analyses of front event properties including occurrence frequency and propagation velocity. Sensitivity tests for the method’s parameters support that this method can be straightforwardly adapted to track evolving fronts of many types in other regions from both models and observations.

Performance of a One-Dimensional Model of Wave-Driven Nearshore Alongshore Tracer Transport and Decay with Applications for Dry Weather Coastal Pollution

“…The SD Bight model grid covers a 30 km stretch of coastline from 32.45 N (south of PB) to 32.75 N (around Point Loma) and extends 10 km offshore (Figure b). The SD Bight model has been used in other recent studies investigating the transport of tracers across the surf zone and inner shelf in the US/MX border region. ,,− The model uses the COAWST (Coupled-Ocean-Atmosphere-Wave-Sediment-Transport) modeling system. , The SD Bight model couples Regional Ocean Modeling Systems (ROMS), a 3D hydrostatic ocean model with terrain-following vertical coordinates, with the Simulating WAves Nearshore (SWAN) model . The resulting model resolves surf zone, estuary, and shelf dynamics.…”

“…The SD Bight model has been used in other recent studies investigating the transport of tracers across the surf zone and inner shelf in the US/MX border region. 14 , 16 , 23 − 25 The model uses the COAWST (Coupled-Ocean-Atmosphere-Wave-Sediment-Transport) modeling system. 26 , 27 The SD Bight model couples Regional Ocean Modeling Systems (ROMS), a 3D hydrostatic ocean model with terrain-following vertical coordinates, 28 with the Simulating WAves Nearshore (SWAN) model.…”

Kinematics of an Ebb Plume Front in a Tidal Crossflow

“…Honegger, 2015;D. A. Honegger et al, 2017;Rijnsburger et al, 2018;Spydell et al, 2021;X. Wu et al, 2021) are becoming more common.…”

“…Through the use of remote sensing technologies, spatially and temporally dense observations of surface fronts and internal bores (or jumps) (D. A. Honegger, 2015; D. A. Honegger et al., 2017; Rijnsburger et al., 2018; Spydell et al., 2021; X. Wu et al., 2021) are becoming more common. The water surface manifestations of the front, such as enhanced surface roughness and wave breaking (Lyzenga, 1991; Orton & Jay, 2005; O’Donnell et al., 1998), enable the time‐resolved tracking of plume fronts via X‐band marine radar (Kilcher & Nash, 2010; Pritchard, 2000; Rijnsburger et al., 2018).…”