Detiding Shipboard ADCP Data in Eastern Boundary Current

Abstract

Spatiotemporal fitting by the least squares method is commonly applied to distinguish the mean flow from the tidal current from shipboard ADCP data in coastal ocean. To analyze this technique in a pelagic region of an eastern boundary current system, a 6-yr period of shipboard ADCP data off Baja California is examined. A diverse set of basis functions is studied and a global tidal model is used for comparison purposes. The Gaussian function together with a nodal configuration of one node in the middle and close to the coast of the region is the best option. However, to obtain the optimal solution, the geostrophic flow, which is stronger than the tidal flow and highly variable off Baja California, might be removed prior to fitting the data. In general, the semimajor axis of the tidal ellipse (M2) is parallel to the coast and the phase speed is poleward and parallel to the coast, in agreement with Kelvin wave dynamics. Because the tides in eastern boundary currents are explained by Kelvin wave dynamics, the use of both the velocity field without geostrophic variability and the Gaussian function in the spatiotemporal fitting by least squares technique is a promising tool for detiding shipboard ADCP data from these systems.