Abstract
Abstract. Maximum Cross Correlation (MCC) technique have been used to derive coastal currents from sequential OCM derived suspended sediment concentration (SSC) maps and the MCC currents are integrated with the Ocean surface current analysis-Real time (OSCAR) ocean currents along the coastal regions of the Southern India. OSCAR currents are mainly depended on the oceanographic measurements from the satellite altimeter which have limitations in the coastal region and in representing the mesoscale properties dominating the coastal ocean. Sequential pair of atmospherically corrected and georeferenced OCM image is used to derive SSC, along the southern coast of India. Maximum Cross-Correlation (MCC) method is applied on the sequential time lapsed images of OCM for matching the suspended sediment dispersion patterns. The MCC technique involves computing of cross-correlation coefficients and identifying correlation peaks. The spatial change of the sediment pattern occurs due to the advection by the currents and the extent of the change corresponds to the speed and direction of the current. From the first image, template window is selected, which is searched in the second image within large region defined as the search window. The movement of the SSC pattern is calculated based on the maximum cross correlation in successive images. Error statistics are calculated between the spatially coherent MCC vectors and OSCAR currents. Based on statistical analysis, an error threshold of 30 degree for current direction and 0.06m/sec for current speed was given to MCC currents and MCC currents beyond the error limit are rejected, while the MCC current within the error limit is merged with the OSCAR ocean currents. The merging of MCC currents has spatially enhanced the OSCAR currents. MCC method is significant in calculating the coastal currents and its mesoscale properties, which dominate the coastal surface flow field and can be used in supplementing the OSCAR ocean currents. Merging of both the currents, have effectively resulted in preparing contiguous maps of coastal ocean currents.
Highlights
Under the present state of art remote sensing capabilities, synoptic observation of ocean current from satellite born data is from altimeter observations
Satellite altimeter observation forms the major component in the Ocean surface current analysis-Real time (OSCAR) ocean current, which is used by the scientific community in studying the ocean surface current patterns
The study shows a practical approach towards the use of sequential Ocean Colour Monitor (OCM) data for deriving current vectors through Maximum Cross Correlation (MCC) method
Summary
Under the present state of art remote sensing capabilities, synoptic observation of ocean current from satellite born data is from altimeter observations. Satellite altimeter observation forms the major component in the Ocean surface current analysis-Real time (OSCAR) ocean current, which is used by the scientific community in studying the ocean surface current patterns. Oceanographic measurements from the satellite altimeter are unable to yield the relatively small scale currents at the coast. Currents derived from nadir sampling altimeters has limited representations of the actual surface flow, since the along-track-only measurements of sea surface heights estimates only the cross-track component of the surface geostrophic velocity. The altimeter derived currents are not valid along the coast due to the proximity of the land features. The satellite altimeters are unable to measure the velocity of geostrophic currents
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