The global optimal surface velocity field near shoreline from infrared images

Abstract

The Global Optimal Solution (GOS) provides surface velocities from Advanced Very High Resolution Radiometer (AVHRR) remote image sequences by using bilinear interpolation algorithms. A highly accurate velocity field can be estimated by GOS with infrared image sequence, but the field has only first order continuity. This paper deals with the use of GOS, but with higher order continuity and smoothed cutouts around coastland edges to estimate surface velocities. Since an actual coastal ocean has a complex, irregular coastland, and some ocean studies need vorticity and divergence analysis which must be extracted from the velocity field, the development of generic GOS algorithms with higher order continuity and smoothed cutouts around these edges is very important. In this paper, the GOS bilinear polynomials, formerly applied only to square tiles with first order continuity, are replaced by surface B-Splines functions. The new GOS algorithms can be applied to AVHRR images containing complicated coastal land boundaries - or even clouds - to yield smooth velocity fields next to land, and higher order continuity velocity field can be obtained. The main advantages of the new GOS are that the highly accurate solution is global optimized, linear, and high order smoothed. The high order GOS velocity fields with those from the numerical model and from the first order GOS technique are compared. Results of applying these methods to two real image sequences are presented. It is demonstrated in this paper that this high order GOS technique to two sequences of NOAA satellite AVHRR images taken in the New York Bight to calculate a velocity field adjacent to the land. I found that all results of the angular and magnitude errors of the velocity by 1 st and 3 rd order GOS are quite close for both numerical model data and AVHRR image sequences, but velocity field estimated by 3 rd order GOS is global smoothed.