Meeting Abstracts
A mixed Lagrangian-Eulerian advection scheme for estimating the trajectories of tracers in ocean models
Nathan Paldor, Yona Dvorkin
The Hebrew University of Jerusalem
(Abstract received 05/14/2012 for session D)
ABSTRACT
In forecasting the trajectory of tracers on the ocean one often employs an Ocean General Circulation Model (OGCM) to advect the tracer with the model's calculated velocity. This straightforward procedure imposes the continuity equation, satisfied by the calculated water velocity on the tracer trajectory even though the latter does not have to satisfy this equation. In order to improve the calculation of the tracer's trajectory without resorting to sophisticated diffusion terms a simple algorithm that combines the model (Eulerian) velocity with a Lagrangian velocity calculated from the model's pressure field and Coriolis force has been developed. The only free parameter of this algorithm is the relative weight of the two velocities that are used in forming the velocity with which the tracer is advected. Application of the proposed algorithm to subsurface floats in the ocean demonstrate drastic improvement in the calculate trajectory compared to advection by the fluid velocity. It is hoped that further development of this idea using data gathered as part the Gulf of Mexico Research Initiative will yield a concrete basis for the general use of the proposed algorithm in similar cases of oil spills. In my talk I'll discuss the possible inclusion of surface forcing (wind) in the algorithm by comparing its performance in cases of surface drifters to that of subsurface ones.