ESTIMACIÓN DE PATRONES DE CIRCULACIÓN SUPERFICIAL EN EL GOLFO DE CALIFORNIA A PARTIR DE IMÁGENES DE SENSORES REMOTOS PASIVOS

Abstract

xx Abstract Ocean surface currents play influence in the distribution of suspended and dissolved material, so the study of the ocean circulation as a dispersal mechanism is a relevant topic in Oceanology. The first estimations of the surface circulation in the Gulf of California were based on reports of drifting ships, and later estimated from hydrographic data, lagrangian measurements, and more recently interpreting satellite images and the development of numerical models. Here is examined the potential of estimating surface velocities using a feature tracking method applied to sea surface temperature images to generate high spatial resolution vector fields. Ocean color images were also analyzed in order to detect mesoscale structures. For this purpose a pattern recognition algorithm applied to pairs of sub-images corresponding to common regions in sequential scenes was developed, which allowed inferring displacement speeds of such sub-images. To implement this algorithm, a database of 360 images of sea surface temperature was formed. The temperature values correspond to daily data (2009-2010) from 6 satellites, interpolated at 1 km spatial to eliminate cloud cover. In addition, ~5500 (2004-2008) ocean color images from MODIS/Aqua sensor were processed, applying algorithms to estimate the relative distribution of total suspended material (TSM), with a spatial resolution of 500 m. As a result of the feature tracking algorithm an average of ~18,000 vectors for each pair of scenes of surface temperature were obtained. Based on these data, monthly averages of direction and speed by geographic location were calculated, generating a spatially dense grid in order to trace trajectories of advective transport. The traced trajectories reproduced some circulation patterns described with numerical models, and speeds are of the same order of magnitude. Compared with displacements of drifting buoys, estimated speeds with this method were ~30% lower. The obtained vector fields can be incorporated as the initial state of numerical models, as well as the simulation of particle surface advective transport. Structures detected with MODIS images were most evident during periods of increased runoff from the drainage basins, revealing TSM plumes that reach extensions up to 44,000 km2, filaments crossing the Gulf from East to West, as well as cyclonic and anticyclonic gyres on the order of 10 to 100 km in diameter. These observations