Observations of oceanic mesoscale features and variability in the Canary Islands area from ERS-1 altimeter data, satellite infrared imagery and hydrographic measurements

Piedra-Fernández

IEEE J. Sel. Top. Appl. Earth Observations Remote Sensing

et al. 2015

Abstract-The ocean covers over 70% of the surface of our planet and plays a key role in the global climate. Most ocean circulation is mesoscale (scales of 50-500 km and 10-100 days), and the energy in mesoscale circulation is at least one order of magnitude greater than general circulation; therefore, the study of mesoscale oceanic structures (MOS) is crucial to ocean dynamics, making it especially useful for analyzing global changes. The detection of MOS, such as upwellings or eddies, from satellites images is significant for marine environmental studies and coastal resource management. In this paper, we present an objectbased image analysis (OBIA) system which segments and classifies regions contained in sea-viewing field-of-view sensor (SeaWiFS) and Moderate Resolution Imaging Spectro-radiometer (MODIS)-Aqua sensor satellite images into MOS. After color clustering and hierarchical data format (HDF) file processing, the OBIA system segments images and extracts image descriptors, producing primary regions. Then, it merges regions, recalculating image descriptors for MOS identification and definition. First, regions are labeled by a human-expert, who identifies MOS: upwellings, eddies, cool, and warm eddies. Labeled regions are then classified by learning algorithms (i.e., decision tree, Bayesian network, artificial neural network, genetic algorithm, and near neighbor algorithm) from selected features. Finally, the OBIA system enables images to be queried from the user interface and retrieved by means of fuzzy descriptors and oceanic structures. We tested our system with images from the Canary Islands and the North West African coast.Index Terms-Automatic recognition, fuzzy logic, image retrieval, moderate resolution imaging spectro-radiometer (MODIS), object-based image analysis (OBIA), ocean satellite images, sea-viewing field-of-view sensor (SeaWiFS).

Section: A Ocean Phenomenamentioning

confidence: 99%

“…In this area, there are many MOS throughout the year. Many works have described the MOS in this area [8], [22]- [25].…”

Section: A Ocean Phenomenamentioning

confidence: 99%

OBIA System for Identifying Mesoscale Oceanic Structures in SeaWiFS and MODIS-Aqua Images

Piedra-Fernández

IEEE J. Sel. Top. Appl. Earth Observations Remote Sensing

et al. 2015

“…They may appear rounded near islands or in the open ocean. In cool eddies, cold nutrient-rich water rises to the surface [18], while warm eddies (see Fig. 1) drag water with organic material to the ocean floor and keep in the warm surface.…”

Section: Introductionmentioning

confidence: 99%

Extraction of Knowledge Rules for the Retrieval of Mesoscale Oceanic Structures in Ocean Satellite Images

Hybrid Soft Computing for Image Segmentation

Piedra

et al. 2016

The processing of ocean satellite images has as goal the detection of phenomena related with ocean dynamics. In this context, Mesoscale Oceanic Structures (MOS) play an essential role. In this chapter we will present the tool developed in our group in order to extract knowledge rules for the retrieval of MOS in ocean satellite images. We will describe the implementation of the tool: the workflow associated with the tool, the user interface, the class structure, and the database of the tool. Additionally, the experimental results obtained with the tool in terms of fuzzy knowledge rules as well as labeled structures with these rules are shown. These results have been obtained with the tool analyzing chlorophyll and temperature images of the Canary Islands and North West African coast captured by the SeaWiFS and MODIS-Aqua sensors.

“…The zone selected for our study, the Northwest African area, presents conditions appropriate for the formation of MOS, such as upwellings, filaments, cold and warm eddies, and wakes, throughout the year (García-Weil et al (2000); Barton et al (1998); Arístegui et al (1994); Sangra et al (2005); Tejera et al (2002); Meunier et al (2012)) (see Figure 1).…”

Section: Introductionmentioning

confidence: 99%

“…In cool eddies, cold nutrient-rich water rises to the surface in counterclockwise swirls (Tejera et al (2002)). The opposite, warm eddies (see Figure 1), drag water with organic matter down to the ocean floor, leaving warm water on the surface, and are formed under stronger wind conditions.…”

Section: Introductionmentioning

confidence: 99%

A location-based approach to the classification of mesoscale oceanic structures in SeaWiFS and Aqua-MODIS images of Northwest Africa

Piedra-Fernández

International Journal of Remote Sensing

et al. 2015

Self Cite

This study presents a different approach to the classification of Mesoscale Oceanic Structures (MOS) present in the Northwest African area, based on their location. The main improvement stems from the partition of this area in four large zones perfectly differentiated by their morphological characteristics, with attention to seafloor topography and coastal relief. This decomposition makes it easier to recognize structures under adverse conditions, basically the presence of clouds partly hiding them. This is observed particularly well in upwellings, which are usually very large structures with a different morphology and genesis in each zone. This approach not only improves the classification of the upwellings, but also makes it possible to analyse changes in the MOS over time, thereby improving the prediction of its morphological evolution. To identify and label the MOS classified in the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) and Aqua-MODIS (Moderate Resolution Imaging Spectroradiometer) chlorophyll-a and temperature images, we used a tool specifically designed by our group for this purpose and which has again shown its validity in this new proposal.