COMPARISON OF SATELLITE AND DRIFTER SURFACE FLOW ESTIMATES IN THE NORTHWESTERN GULF-OF-MEXICO

A comparison of flow observations has been made with drifting buoys and infrared satellite images for northwestern Gulf of Mexico surface waters during the interval from 10 March to 23 April, 1989. Each drifter was drogued to a depth of 2.7 m and reported four-nine positions along its trajectory every 24 h through the NOAA satellite Argos data collection system. Corresponding flow observations were computed from sequential infrared imagery obtained by Advanced Very-High Resolution Radiometer (AVHRR) on the same satellites. Vector estimates of advective motion were extracted from surface temperature pattern displacements between images paired at 24 and 12 h intervals without knowledge of the drifter trajectories. Twenty-two blind test cases at 24 h intervals formed the data base for examining the relative accuracy between trajectories simulated with satellite flow estimates and those obtained with the drifters. The comparison of actual and computed velocities for 24 h displacements resulted in a counterclockwise regression angle of simulated to actual velocities of -1.7-degrees, a standard error in estimates of simulated speeds from actual speeds of 5.5 cm s-1 for actual speeds in the range from 0 to 60 cm s-1, and a regression complex coefficient of determination (rho2) of 0.936. The study indicates a convergence of results for the satellite image and Argos drifter methods of surface flow estimation and a combined capacity to investigate inertial range circulation variability.