Abstract

We explore the potential of computing coastal ocean surface currents from Moderate-Resolution Imaging Spectroradiometer (MODIS) and Visible Infrared Imaging Radiometer Suite (VIIRS) satellite imagery using the maximum cross-correlation (MCC) method. To improve on past versions of this method, we evaluate combining MODIS and VIIRS thermal infrared (IR) and ocean color (OC) imagery to map the coastal surface currents and discuss the benefits of this combination of sensors and optical channels. By combining these two sensors, the total number of vectors increases by 58.3 % . In addition, we also make use of the different surface patterns of IR and OC imagery to improve the tracking performance of the MCC method. By merging the MCC velocity fields inferred from IR and OC products, the spatial coverage of each individual MCC field is increased by 65.8 % relative to the vectors derived from OC images. The root mean square (RMS) error of the merged currents is 18 cm · s − 1 compared with coincident HF radar surface currents. A 5-year long time serious of merged MCC computed currents was used to investigate the current structure of the California Current (CC). Weekly, seasonal, and 5-year mean flows provide a unique space-time picture of the oceanographic variability of the CC.

Highlights

  • Mapping of costal surface currents, and their space-time variability, is one of the major challenges in physical oceanography

  • Wi = wi − wi where i is the index of the corresponding pixel of the two datasets; wi is scalar value that represents the u- component, v- component, magnitude and direction of the current vector or the complex correlation coefficient estimated with the maximum cross-correlation (MCC) method; wi is the corresponding value estimated from HF radar

  • We explore the potential to map the coastal currents using the improved MCC method from the combination of Moderate-Resolution Imaging Spectroradiometer (MODIS) and Visible Infrared Imaging Radiometer Suite (VIIRS) imagery

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Summary

Introduction

Mapping of costal surface currents, and their space-time variability, is one of the major challenges in physical oceanography. Sequential synthetic aperture radar (SAR) images derived from ERS-2, Envisat [16], TerraSAR-X (TSX) [17], TanDEM-X (TDX) and COSMO-SkyMed (CSK) [18] have been used with the MCC method to map the space-time variations of coastal currents. The MODIS and VIIRS provide global thermal IR and OC satellite datasets, which can be used to compute coastal surface currents with the MCC method. We explore the potential of mapping the coastal surface currents by combining MODIS and VIIRS satellite imagery.

Study Region
Satellite Imagery
HF Radar Currents
MCC Method
Combination of MODIS and VIIRS Imagery
Comparison with HF Radar Currents
Multiple MCC Source Image Current Merging
Routine MCC Current Computation
Number of Vectors
MCC Current Composites
California Current System Observation
Seasonal MCC Mean Flows
Findings
Discussion and Conclusions
Full Text
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