Evan Mason - Academia.edu (original) (raw)

Papers by Evan Mason

Oceanography of the Mediterranean Sea

Frontiers in Marine Science

After the launch of the Surface Water and Ocean Topography (SWOT) satellite planned for 2022, the... more After the launch of the Surface Water and Ocean Topography (SWOT) satellite planned for 2022, the region around the Balearic Islands (western Mediterranean Sea) will be the target of several in situ sampling campaigns aimed at validating the first available tranche of SWOT data. In preparation for this validation, the PRE-SWOT cruise in 2018 was conceived to explore the three-dimensional (3D) circulation at scales of 20 km that SWOT aims to resolve, included in the fine-scale range (1–100 km) as defined by the altimetric community. These scales and associated variability are not captured by contemporary nadir altimeters. Temperature and salinity observations reveal a front that separates local Atlantic Water in the northeast from recent Atlantic Water in the southeast, and extends from the surface to ~150 m depth with maximum geostrophic velocities of the order of 0.20 m s−1 and a geostrophic Rossby number that ranges between −0.24 and 0.32. This front is associated with a 3D vertic...

Earth System Science Data, 2022

This paper presents the new global Mesoscale Eddy Trajectory Atlases (META3.1exp DT allsatellites,

New Frontiers in Operational Oceanography, 2018

High-resolution regional models of the ocean circulation are now operated on a routine basis usin... more High-resolution regional models of the ocean circulation are now operated on a routine basis using realistic setups in many regions of the world, with the aim to be used for both scientific purposes and practical applications involving decision-making processes. While the evaluation of these simulations is essential for the provision of reliable information to users and allows the identification of areas of model improvement, it also highlights several challenges. Observations are limited and the real state of the ocean is, to a large extent, unknown at the short spatiotemporal scales resolved in these models. The skill of the model also generally varies with the region, variable, depth and the spatiotemporal scale under consideration. Moreover, the increased spatial resolution might require ad hoc metrics to properly reflect the model performance and reduce the impact of so-called "double-penalty" effects occurring when using point-topoint comparisons with features present in the model but misplaced with respect to the observations. Multiplatform observations currently collected through regional and coastal ocean observatories constitute very valuable databases to evaluate the simulations. Gliders, high frequency radars, moorings, Lagrangian surface drifters, and profiling floats all provide, with their own specific sampling capability, partial but accurate information about the ocean and its variability at different scales. This is complementary to the global measurements collected from satellites. Using a case study in the Western Mediterranean Sea, this chapter illustrates the opportunities offered by multi-platform measurements to assess the realism of highresolution regional model simulations.

A high-resolution numerical model study of the Canary Basin in the northeast subtropical Atlantic... more A high-resolution numerical model study of the Canary Basin in the northeast subtropical Atlantic Ocean is presented. A long-term climatological solution from the Regional Oceanic Modeling System (ROMS) reveals mesoscale variability associated with the Azores and Canary Current systems, the northwest African coastal upwelling, and the Canary Island archipelago. The primary result concerns the Canary Current (CanC) which, in the solution, transports ∼3 Sv southward in line with observations. The simulated CanC has a well-defined path with pronounced seasonal variability. This variability is shown to be mediated by the westward passage of two large annually excited counterrotating anomalous structures that originate at the African coast. The anomalies have a sea surface expression, permitting their validation using altimetry and travel at the phase speed of baroclinic planetary (Rossby) waves. The role of nearshore wind stress curl variability as a generating mechanism for the anomalies is confirmed through a sensitivity experiment forced by low-resolution winds. The resulting circulation is weak in comparison to the base run, but the propagating anomalies are still discernible, so we cannot discount a further role in their generation being played by annual reversals of the large-scale boundary flow that are known to occur along the African margin. An additional sensitivity experiment, where the Azores Current is removed by closing the Strait of Gibraltar presents the same anomalies and CanC behavior as the base run, suggesting that the CanC is rather insensitive to upstream variability from the Azores Current.

Trabajo presentado en la Ocean Sciences Meeting, celebrada en Nueva Orleans, Estados Unidos, del ... more Trabajo presentado en la Ocean Sciences Meeting, celebrada en Nueva Orleans, Estados Unidos, del 21 al 26 de febrero de 2016

Trabajo presentado en el Black Sea from Space Workshop, celebrado en Constanta, Rumania, del 28 a... more Trabajo presentado en el Black Sea from Space Workshop, celebrado en Constanta, Rumania, del 28 al 30 de septiembre de 2016

In this study, we evaluate how a new revision of the satellite sea level anomaly maps released by... more In this study, we evaluate how a new revision of the satellite sea level anomaly maps released by AVISO in April 2014 affects the representation of mesoscale eddies in the Eastern Boundary Upwelling Systems (EBUS). Due to a finer effective resolution, the new product enables the detection of more eddies (+37%) and also shows changes in eddy characteristics, most notably a tendency for smaller eddy radius estimates.

IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium, 2018

This work presents EddyNet, a deep learning based architecture for automated eddy detection and c... more This work presents EddyNet, a deep learning based architecture for automated eddy detection and classification from Sea Surface Height (SSH) maps provided by the Copernicus Marine and Environment Monitoring Service (CMEMS). EddyNet consists of a convolutional encoder-decoder followed by a pixelwise classification layer. The output is a map with the same size of the input where pixels have the following labels {'0': Non eddy, '1': anticyclonic eddy, '2': cyclonic eddy}. Keras Python code, the training datasets and EddyNet weights files are open-source and freely available on https://github.com/redouanelg/EddyNet.

Advances in Space Research, 2021

In 2018 we celebrated 25 years of development of radar altimetry, and the progress achieved by th... more In 2018 we celebrated 25 years of development of radar altimetry, and the progress achieved by this methodology in the fields of global and coastal oceanography, hydrology, geodesy and cryospheric sciences. Many symbolic major events have celebrated these developments, e.g., in Venice, Italy, the 15th (2006) and 20th (2012) years of progress and more recently, in 2018, in Ponta Delgada, Portugal, 25 Years of Progress in Radar Altimetry. On this latter occasion it was decided to collect contributions of scientists, engineers and managers involved in the worldwide altimetry community to depict the state of altimetry and propose recommendations for the altimetry of the future. This paper summarizes contributions and recommendations that were collected and provides guidance for future mission design, research activities, and sustainable operational radar altimetry data exploitation. Recommendations provided are fundamental for optimizing further scientific and operational advances of oceanographic observations by altimetry, including requirements for spatial and temporal resolution of altimetric measurements, their accuracy and continuity. There are also new challenges and new openings mentioned in the paper that are particularly crucial for observations at higher latitudes, for coastal oceanography, for cryospheric studies and for hydrology. The paper starts with a general introduction followed by a section on Earth System Science including Ocean Dynamics, Sea Level, the Coastal Ocean, Hydrology, the Cryosphere and Polar Oceans and the ''Green" Ocean, extending the frontier from biogeochemistry to marine ecology. Applications are described in a subsequent section, which covers Operational Oceanography, Weather, Hurricane Wave and Wind Forecasting, Climate projection. Instruments' development and satellite missions' evolutions are described in a fourth section. A fifth section covers the key observations that altimeters provide and their potential complements, from other Earth observation measurements to in situ data. Section 6 identifies the data and methods and provides some accuracy and resolution requirements for the wet tropospheric correction, the orbit and other geodetic requirements, the Mean Sea Surface, Geoid and Mean Dynamic Topography, Calibration and Validation, data accuracy, data access and handling (including the DUACS system). Section 7 brings a transversal view on scales, integration, artificial intelligence, and capacity building (education and training). Section 8 reviews the programmatic issues followed by a conclusion.

Progress in Oceanography, 2020

Journal of Physical Oceanography, 2019

The complex structure of the vertical velocity field inside an anticyclonic eddy located just sou... more The complex structure of the vertical velocity field inside an anticyclonic eddy located just south of the Canary Islands is analyzed through a high-resolution ocean model. Based on the flow divergence, vertical velocity is decomposed into various forcing components. The analysis reveals that advection and stretching of vorticity are the most important forcing contributions to the vertical velocity within the eddy. In the mixed layer, a small-scale multipolar vertical velocity pattern dominates. This is the result of vertical mixing effects that enhance the surface vertical velocity by increasing the ageostrophic velocity profile. As a result, an ageostrophic secondary circulation arises that acts to restore thermal-wind balance, inducing strong vertical motions. Nonlinear Ekman pumping/suction patterns resemble the small-scale vertical velocity field, suggesting that nonlinear Ekman effects are important in explaining the complex vertical velocity, despite an overestimate of its ma...

Ocean Science, 2019

Rapid evolution of operational ocean forecasting systems is driven by advances in numerics and da... more Rapid evolution of operational ocean forecasting systems is driven by advances in numerics and data assimilation schemes, and increase of in situ and satellite observations. The Copernicus Marine Service (CMEMS) is a major provider of operational products that are made available through an online catalogue. The service includes global and regional forecasts in near-real-time and reanalysis modes. Here, we apply an eddy tracker to daily sea surface height (SSH) fields from three such reanalysis products from the CMEMS catalogue, with the objective to evaluate their performance in terms of their eddy properties and three-dimensional composite structures over the 2013-2016 period. The products are (i) the Global Analysis Forecast, (ii) the Mediterranean Analysis Forecast and (iii) the Iberia-Biscay-Ireland Analysis Forecast. The common domain between these reanalyses is the western Mediterranean Sea (WMED) between the Strait of Gibraltar and Sardinia. This is a complex region with strong density gradients, especially in the Alboran Sea in the west where Atlantic and Mediterranean waters compete. Surface eddy property maps over the WMED of eddy radii, amplitudes and nonlinearity are consistent between the models, as well as with gridded altimetric data that serve as a reference. Mean 3-D eddy composites are shown only for three subregions in the Alboran Sea. These are mostly consistent between the models, with minor differences being attributed to details of the respective model configurations. This information can be informative for the ongoing development of these CMEMS operational modeling systems. The mesoscale data provided here may be of interest to CMEMS users and in the future could be a useful addition to a more diverse CMEMS catalogue.

Remote Sensing, 2018

The aim of this study is to assess the capacity of the Surface Water Ocean Topography (SWOT) sate... more The aim of this study is to assess the capacity of the Surface Water Ocean Topography (SWOT) satellite to resolve fine scale oceanic surface features in the western Mediterranean. Using as input the Sea Surface Height (SSH) fields from a high-resolution Ocean General Circulation Model (OGCM), the SWOT Simulator for Ocean Science generates SWOT-like outputs along a swath and the nadir following the orbit ground tracks. Given the characteristic temporal and spatial scales of fine scale features in the region, we examine temporal and spatial resolution of the SWOT outputs by comparing them with the original model data which are interpolated onto the SWOT grid. To further assess the satellite's performance, we derive the absolute geostrophic velocity and relative vorticity. We find that instrument noise and geophysical error mask the whole signal of the pseudo-SWOT derived dynamical variables. We therefore address the impact of removal of satellite noise from the pseudo-SWOT data using a Laplacian diffusion filter, and then focus on the spatial scales that are resolved within a swath after this filtering. To investigate sensitivity to different filtering parameters, we calculate spatial spectra and root mean square errors. Our numerical experiments show that noise patterns dominate the spectral content of the pseudo-SWOT fields at wavelengths below 60 km. Application of the Laplacian diffusion filter allows recovery of the spectral signature within a swath down to the 40-60 km wavelength range. Consequently, with the help of this filter, we are able to improve the observation of fine scale oceanic features in pseudo-SWOT data, and in the estimation of associated derived variables such as velocity and vorticity.

Ocean Science Discussions, 2019

Rapid evolution of operational ocean models is driven by advances in numerics and sophisticated d... more Rapid evolution of operational ocean models is driven by advances in numerics and sophisticated data assimilation schemes, computational power, and storage capacity. The Copernicus Marine Service (CMEMS) is a major provider of operational products that are made available through an online catalogue. The service includes global and regional forecasts in near-real-time and reanalysis modes. Here we apply an eddy tracker to daily SSH fields from three such reanalysis products from the CMEMS catalogue, with the objective to evaluate their performance in terms of their eddy properties and three-dimensional composite structures over the period 2013 through 2016. The products are (i) the Global Analysis Forecast, (ii) the Mediterranean Analysis Forecast, and (iii) the Iberia-Biscay-Ireland Analysis Forecast. The common domain between these reanalyses is the western Mediterranean Sea (WMED) between the Strait of Gibraltar and Sardinia. This is a complex region with strong density gradients, especially in the Alboran Sea in the west where Atlantic and Mediterranean waters compete. Surface eddy property maps over the WMED of eddy radii, amplitudes and nonlinearity are consistent between the models, as well as with gridded altimetric data that serve as a reference. Mean 3D eddy composites are shown only for three subregions in the Alboran Sea. These are mostly consistent between the models, with minor differences being attributed to details of the respective model configurations. This information can be informative for the ongoing development of these CMEMS operational modeling systems.

Oceanography of the Mediterranean Sea

Frontiers in Marine Science

After the launch of the Surface Water and Ocean Topography (SWOT) satellite planned for 2022, the... more After the launch of the Surface Water and Ocean Topography (SWOT) satellite planned for 2022, the region around the Balearic Islands (western Mediterranean Sea) will be the target of several in situ sampling campaigns aimed at validating the first available tranche of SWOT data. In preparation for this validation, the PRE-SWOT cruise in 2018 was conceived to explore the three-dimensional (3D) circulation at scales of 20 km that SWOT aims to resolve, included in the fine-scale range (1–100 km) as defined by the altimetric community. These scales and associated variability are not captured by contemporary nadir altimeters. Temperature and salinity observations reveal a front that separates local Atlantic Water in the northeast from recent Atlantic Water in the southeast, and extends from the surface to ~150 m depth with maximum geostrophic velocities of the order of 0.20 m s−1 and a geostrophic Rossby number that ranges between −0.24 and 0.32. This front is associated with a 3D vertic...

Earth System Science Data, 2022

This paper presents the new global Mesoscale Eddy Trajectory Atlases (META3.1exp DT allsatellites,

New Frontiers in Operational Oceanography, 2018

High-resolution regional models of the ocean circulation are now operated on a routine basis usin... more High-resolution regional models of the ocean circulation are now operated on a routine basis using realistic setups in many regions of the world, with the aim to be used for both scientific purposes and practical applications involving decision-making processes. While the evaluation of these simulations is essential for the provision of reliable information to users and allows the identification of areas of model improvement, it also highlights several challenges. Observations are limited and the real state of the ocean is, to a large extent, unknown at the short spatiotemporal scales resolved in these models. The skill of the model also generally varies with the region, variable, depth and the spatiotemporal scale under consideration. Moreover, the increased spatial resolution might require ad hoc metrics to properly reflect the model performance and reduce the impact of so-called "double-penalty" effects occurring when using point-topoint comparisons with features present in the model but misplaced with respect to the observations. Multiplatform observations currently collected through regional and coastal ocean observatories constitute very valuable databases to evaluate the simulations. Gliders, high frequency radars, moorings, Lagrangian surface drifters, and profiling floats all provide, with their own specific sampling capability, partial but accurate information about the ocean and its variability at different scales. This is complementary to the global measurements collected from satellites. Using a case study in the Western Mediterranean Sea, this chapter illustrates the opportunities offered by multi-platform measurements to assess the realism of highresolution regional model simulations.

A high-resolution numerical model study of the Canary Basin in the northeast subtropical Atlantic... more A high-resolution numerical model study of the Canary Basin in the northeast subtropical Atlantic Ocean is presented. A long-term climatological solution from the Regional Oceanic Modeling System (ROMS) reveals mesoscale variability associated with the Azores and Canary Current systems, the northwest African coastal upwelling, and the Canary Island archipelago. The primary result concerns the Canary Current (CanC) which, in the solution, transports ∼3 Sv southward in line with observations. The simulated CanC has a well-defined path with pronounced seasonal variability. This variability is shown to be mediated by the westward passage of two large annually excited counterrotating anomalous structures that originate at the African coast. The anomalies have a sea surface expression, permitting their validation using altimetry and travel at the phase speed of baroclinic planetary (Rossby) waves. The role of nearshore wind stress curl variability as a generating mechanism for the anomalies is confirmed through a sensitivity experiment forced by low-resolution winds. The resulting circulation is weak in comparison to the base run, but the propagating anomalies are still discernible, so we cannot discount a further role in their generation being played by annual reversals of the large-scale boundary flow that are known to occur along the African margin. An additional sensitivity experiment, where the Azores Current is removed by closing the Strait of Gibraltar presents the same anomalies and CanC behavior as the base run, suggesting that the CanC is rather insensitive to upstream variability from the Azores Current.

Trabajo presentado en la Ocean Sciences Meeting, celebrada en Nueva Orleans, Estados Unidos, del ... more Trabajo presentado en la Ocean Sciences Meeting, celebrada en Nueva Orleans, Estados Unidos, del 21 al 26 de febrero de 2016

Trabajo presentado en el Black Sea from Space Workshop, celebrado en Constanta, Rumania, del 28 a... more Trabajo presentado en el Black Sea from Space Workshop, celebrado en Constanta, Rumania, del 28 al 30 de septiembre de 2016

In this study, we evaluate how a new revision of the satellite sea level anomaly maps released by... more In this study, we evaluate how a new revision of the satellite sea level anomaly maps released by AVISO in April 2014 affects the representation of mesoscale eddies in the Eastern Boundary Upwelling Systems (EBUS). Due to a finer effective resolution, the new product enables the detection of more eddies (+37%) and also shows changes in eddy characteristics, most notably a tendency for smaller eddy radius estimates.

IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium, 2018

This work presents EddyNet, a deep learning based architecture for automated eddy detection and c... more This work presents EddyNet, a deep learning based architecture for automated eddy detection and classification from Sea Surface Height (SSH) maps provided by the Copernicus Marine and Environment Monitoring Service (CMEMS). EddyNet consists of a convolutional encoder-decoder followed by a pixelwise classification layer. The output is a map with the same size of the input where pixels have the following labels {'0': Non eddy, '1': anticyclonic eddy, '2': cyclonic eddy}. Keras Python code, the training datasets and EddyNet weights files are open-source and freely available on https://github.com/redouanelg/EddyNet.

Advances in Space Research, 2021

In 2018 we celebrated 25 years of development of radar altimetry, and the progress achieved by th... more In 2018 we celebrated 25 years of development of radar altimetry, and the progress achieved by this methodology in the fields of global and coastal oceanography, hydrology, geodesy and cryospheric sciences. Many symbolic major events have celebrated these developments, e.g., in Venice, Italy, the 15th (2006) and 20th (2012) years of progress and more recently, in 2018, in Ponta Delgada, Portugal, 25 Years of Progress in Radar Altimetry. On this latter occasion it was decided to collect contributions of scientists, engineers and managers involved in the worldwide altimetry community to depict the state of altimetry and propose recommendations for the altimetry of the future. This paper summarizes contributions and recommendations that were collected and provides guidance for future mission design, research activities, and sustainable operational radar altimetry data exploitation. Recommendations provided are fundamental for optimizing further scientific and operational advances of oceanographic observations by altimetry, including requirements for spatial and temporal resolution of altimetric measurements, their accuracy and continuity. There are also new challenges and new openings mentioned in the paper that are particularly crucial for observations at higher latitudes, for coastal oceanography, for cryospheric studies and for hydrology. The paper starts with a general introduction followed by a section on Earth System Science including Ocean Dynamics, Sea Level, the Coastal Ocean, Hydrology, the Cryosphere and Polar Oceans and the ''Green" Ocean, extending the frontier from biogeochemistry to marine ecology. Applications are described in a subsequent section, which covers Operational Oceanography, Weather, Hurricane Wave and Wind Forecasting, Climate projection. Instruments' development and satellite missions' evolutions are described in a fourth section. A fifth section covers the key observations that altimeters provide and their potential complements, from other Earth observation measurements to in situ data. Section 6 identifies the data and methods and provides some accuracy and resolution requirements for the wet tropospheric correction, the orbit and other geodetic requirements, the Mean Sea Surface, Geoid and Mean Dynamic Topography, Calibration and Validation, data accuracy, data access and handling (including the DUACS system). Section 7 brings a transversal view on scales, integration, artificial intelligence, and capacity building (education and training). Section 8 reviews the programmatic issues followed by a conclusion.

Progress in Oceanography, 2020

Journal of Physical Oceanography, 2019

The complex structure of the vertical velocity field inside an anticyclonic eddy located just sou... more The complex structure of the vertical velocity field inside an anticyclonic eddy located just south of the Canary Islands is analyzed through a high-resolution ocean model. Based on the flow divergence, vertical velocity is decomposed into various forcing components. The analysis reveals that advection and stretching of vorticity are the most important forcing contributions to the vertical velocity within the eddy. In the mixed layer, a small-scale multipolar vertical velocity pattern dominates. This is the result of vertical mixing effects that enhance the surface vertical velocity by increasing the ageostrophic velocity profile. As a result, an ageostrophic secondary circulation arises that acts to restore thermal-wind balance, inducing strong vertical motions. Nonlinear Ekman pumping/suction patterns resemble the small-scale vertical velocity field, suggesting that nonlinear Ekman effects are important in explaining the complex vertical velocity, despite an overestimate of its ma...

Ocean Science, 2019

Rapid evolution of operational ocean forecasting systems is driven by advances in numerics and da... more Rapid evolution of operational ocean forecasting systems is driven by advances in numerics and data assimilation schemes, and increase of in situ and satellite observations. The Copernicus Marine Service (CMEMS) is a major provider of operational products that are made available through an online catalogue. The service includes global and regional forecasts in near-real-time and reanalysis modes. Here, we apply an eddy tracker to daily sea surface height (SSH) fields from three such reanalysis products from the CMEMS catalogue, with the objective to evaluate their performance in terms of their eddy properties and three-dimensional composite structures over the 2013-2016 period. The products are (i) the Global Analysis Forecast, (ii) the Mediterranean Analysis Forecast and (iii) the Iberia-Biscay-Ireland Analysis Forecast. The common domain between these reanalyses is the western Mediterranean Sea (WMED) between the Strait of Gibraltar and Sardinia. This is a complex region with strong density gradients, especially in the Alboran Sea in the west where Atlantic and Mediterranean waters compete. Surface eddy property maps over the WMED of eddy radii, amplitudes and nonlinearity are consistent between the models, as well as with gridded altimetric data that serve as a reference. Mean 3-D eddy composites are shown only for three subregions in the Alboran Sea. These are mostly consistent between the models, with minor differences being attributed to details of the respective model configurations. This information can be informative for the ongoing development of these CMEMS operational modeling systems. The mesoscale data provided here may be of interest to CMEMS users and in the future could be a useful addition to a more diverse CMEMS catalogue.

Remote Sensing, 2018

The aim of this study is to assess the capacity of the Surface Water Ocean Topography (SWOT) sate... more The aim of this study is to assess the capacity of the Surface Water Ocean Topography (SWOT) satellite to resolve fine scale oceanic surface features in the western Mediterranean. Using as input the Sea Surface Height (SSH) fields from a high-resolution Ocean General Circulation Model (OGCM), the SWOT Simulator for Ocean Science generates SWOT-like outputs along a swath and the nadir following the orbit ground tracks. Given the characteristic temporal and spatial scales of fine scale features in the region, we examine temporal and spatial resolution of the SWOT outputs by comparing them with the original model data which are interpolated onto the SWOT grid. To further assess the satellite's performance, we derive the absolute geostrophic velocity and relative vorticity. We find that instrument noise and geophysical error mask the whole signal of the pseudo-SWOT derived dynamical variables. We therefore address the impact of removal of satellite noise from the pseudo-SWOT data using a Laplacian diffusion filter, and then focus on the spatial scales that are resolved within a swath after this filtering. To investigate sensitivity to different filtering parameters, we calculate spatial spectra and root mean square errors. Our numerical experiments show that noise patterns dominate the spectral content of the pseudo-SWOT fields at wavelengths below 60 km. Application of the Laplacian diffusion filter allows recovery of the spectral signature within a swath down to the 40-60 km wavelength range. Consequently, with the help of this filter, we are able to improve the observation of fine scale oceanic features in pseudo-SWOT data, and in the estimation of associated derived variables such as velocity and vorticity.

Ocean Science Discussions, 2019

Rapid evolution of operational ocean models is driven by advances in numerics and sophisticated d... more Rapid evolution of operational ocean models is driven by advances in numerics and sophisticated data assimilation schemes, computational power, and storage capacity. The Copernicus Marine Service (CMEMS) is a major provider of operational products that are made available through an online catalogue. The service includes global and regional forecasts in near-real-time and reanalysis modes. Here we apply an eddy tracker to daily SSH fields from three such reanalysis products from the CMEMS catalogue, with the objective to evaluate their performance in terms of their eddy properties and three-dimensional composite structures over the period 2013 through 2016. The products are (i) the Global Analysis Forecast, (ii) the Mediterranean Analysis Forecast, and (iii) the Iberia-Biscay-Ireland Analysis Forecast. The common domain between these reanalyses is the western Mediterranean Sea (WMED) between the Strait of Gibraltar and Sardinia. This is a complex region with strong density gradients, especially in the Alboran Sea in the west where Atlantic and Mediterranean waters compete. Surface eddy property maps over the WMED of eddy radii, amplitudes and nonlinearity are consistent between the models, as well as with gridded altimetric data that serve as a reference. Mean 3D eddy composites are shown only for three subregions in the Alboran Sea. These are mostly consistent between the models, with minor differences being attributed to details of the respective model configurations. This information can be informative for the ongoing development of these CMEMS operational modeling systems.

Filaments are narrow, shallow structures of cool water originating from the coast. They are typic... more Filaments are narrow, shallow structures of cool water originating from the coast. They are typical features of the four main eastern boundary upwelling systems (EBUS). In spite of their significant biological and chemical roles, through the offshore exportation of nutrient-rich waters, the physical processes that generate them are still not completely understood. This paper is a process-oriented study of filament generation mechanisms. Our goal is twofold: firstly, to obtain a numerical solution able to correctly represent the characteristics of the filament off Cape Ghir (30°38′N, northwest Africa) in the Canary EBUS and secondly, to explain its formation by a simple mechanism based on the balance of potential vorticity.The first goal is achieved by the use of the ROMS model (Regional Ocean Modeling System) with embedded domains around Cape Ghir, with a horizontal resolution going up to 1.5 km for the finest domain. The latter gets its initial and boundary conditions from a parent solution and is forced by climatological, high-resolution atmospheric fields. The modeled filaments display spatial, temporal and physical characteristics in agreement with the available in situ and satellite observations. This model solution is used as a reference to compare the results with a set of process-oriented experiments. These experiments allow us to reach the second objective. The solutions serve to highlight the contributions of various processes on the filament generation. Since the study is focused on general processes present under climatological forcing conditions, inter-annual forcing is not necessary.The underlying idea for the filament generation is the balance of potential vorticity in the Canary EBUS: the upwelling jet is characterized by negative relative vorticity and flows southward along a narrow band of uniform potential vorticity. In the vicinity of the cape, an injection of relative vorticity induced by the wind breaks the existing vorticity balance. The upwelling jet is prevented from continuing its way southward and has to turn offshore to follow lines of equal potential vorticity.The model results highlight the essential role of wind, associated with the particular topography (coastline and bottom) around the cape. The mechanism presented here is general and thus can be applied to other EBUS.► The results of a regional model around Cape Ghir are presented and validated. ► An original mechanism based on potential vorticity balance is proposed to explain the filament generation. ► Process-oriented experiments underline the role of the wind in the filament generation.

AbstractWe investigate the extent to which the recently upgraded version of the Ssalto/Duacs sea ... more AbstractWe investigate the extent to which the recently upgraded version of the Ssalto/Duacs sea level anomaly product affects the description of mesoscale activity in the Eastern Boundary Upwelling Systems (EBUS). Drifter observations confirm that the new data set released by Archiving, Validation and Interpretation of Satellite Oceanographic data (AVISO) in April 2014 (DT14) offers an enhanced description of mesoscale activity for the four EBUS. DT14 returns significantly higher eddy kinetic energy levels (+80%) within a 300 km coastal band, where mesoscale structures are known to induce important lateral physical and biogeochemical fluxes. When applied to DT14, an automatic eddy detection algorithm detects more eddies in the EBUS (+37%), and lower eddy radius estimates, in comparison with results using the former altimetry product (DT10). We show that despite higher eddy densities, the smaller eddy radii result in westward eddy transport estimates that are smaller than those obtained from DT10 (−12%).