Lagrangian assessment of simulated surface current dispersion in the coastal ocean

Abstract

A purely Lagrangian assessment of dispersion from modeled surface current trajectories in the coastal ocean is presented. Modeled trajectories come from ROMS simulations for the Southern California Bight during the 1996 through 1999 period. Data are from surface current trajectories collected primarily in the Santa Barbara Channel with CODE style drifters. Distributions of particle positions from trajectories emanating from launch locations within 10 kilometers of the coast throughout the Santa Barbara Channel that advect for one through four days (Lagrangian PDFs) are evaluated descriptively and quantitatively. The two dimensional Kolmogorov‐Smirnov (K‐S) statistical test for comparing discrete sampled data with a known probability distribution is the quantitative basis. In general, dispersion distributions from observations are similar to Lagrangian PDFs computed from modeled trajectories and the K‐S statistic quantifies this accordingly. A few specific regions of poor model‐data agreement are indicated and discussed. The purely Lagrangian assessment, elucidates an improved understanding of model performance and ocean circulation beyond that offered in a Eulerian sense, and is necessary when modeled trajectories are utilized for applied oceanographic and marine ecology problems.