Automatic tool for the precise detection of upwelling and filaments in remote sensing imagery
The upward movement of cool and nutrient-rich waters toward the surface leads to horizontal alterations in the distribution of the physical, chemical, and biological properties. Remote sensing is being extensively applied to detect such coastal upwellings; however, the enormous amount of data daily generated obliges to develop automatic detection and prediction tools. The problem of identifying oceanographic mesoscale structures has been studied using a variety of image processing techniques; however, the outstanding difficulties encountered in the traditional approaches are the presence of noise, the fact that gradients are weak, the strong morphological variation, and the absence of a valid analytical model for the structures. In this context, the proposed automatic upwelling extraction methodology overcomes the preceding detection inconveniences and achieves a highly accurate structure extraction. This automatic technique is based on a coarse-segmentation methodology followed by a fine-detail growing process. The complete system has been validated over a database of 378 multisensorial images of years 2000 to 2003, and it has been applied to the detection and feature extraction of coastal upwellings and filaments in three areas with different characteristics, such as the Canary Islands, Cape Ghir, and the Alboran Sea, using imagery from the Advanced Very High Resolution Radiometer 2 and 3 sensors, the Sea-viewing Wide Field-of-view Sensor, and the Moderate Resolution Imaging Spectroradiometer sensor, demonstrating its effectiveness and robustness in a wide variety of climate conditions.