Computing advective velocities from satellite images of sea surface temperature

摘要

A method of employing sequential satellite images of sea surface temperature (SST) patterns to estimate surface advective current velocities is described. SST images are obtained by processing data received twice daily from the Advanced Very High Resolution Radiometer. The current velocities are estimated by applying a maximum cross correlation (MCC) technique on two time-lapsed images. The MCC technique involves computing matrices of cross correlation coefficients and identifying correlation peaks. A two-stage multilevel statistical test over two-dimensional correlations is developed for determining the relative significance levels of velocity estimates. The test also identifies areas where the MCC technique cannot be effective. Aspects of implementation and limitations of the MCC technique for computing current velocity are also discussed. Advective velocity fields computed through MCC for the Chatham Rise area in New Zealand extending from (40.5 degrees S, 173.5 degrees E) to (49 degrees S, 178 degrees W) show good agreement with the known geostrophic flow patterns in this area.