Articles | Volume 20, issue 6
https://doi.org/10.5194/os-20-1567-2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Special issue:
https://doi.org/10.5194/os-20-1567-2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
02 Dec 2024
Research article |
| 02 Dec 2024
| 02 Dec 2024
Ensemble reconstruction of missing satellite data using a denoising diffusion model: application to chlorophyll a concentration in the Black Sea
GeoHydrodynamics and Environment Research (GHER), FOCUS, University of Liège, Liège, Belgium
Julien Brajard
Nansen Environmental and Remote Sensing Center and Bjerknes Centre for Climate Research, Bergen 5007, Norway
Aida Alvera-Azcárate
GeoHydrodynamics and Environment Research (GHER), FOCUS, University of Liège, Liège, Belgium
Bayoumy Mohamed
GeoHydrodynamics and Environment Research (GHER), FOCUS, University of Liège, Liège, Belgium
Charles Troupin
GeoHydrodynamics and Environment Research (GHER), FOCUS, University of Liège, Liège, Belgium
Jean-Marie Beckers
GeoHydrodynamics and Environment Research (GHER), FOCUS, University of Liège, Liège, Belgium
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Cyril Palerme, Thomas Lavergne, Jozef Rusin, Arne Melsom, Julien Brajard, Are Frode Kvanum, Atle Macdonald Sørensen, Laurent Bertino, and Malte Müller
The Cryosphere, 18, 2161–2176, https://doi.org/10.5194/tc-18-2161-2024, https://doi.org/10.5194/tc-18-2161-2024, 2024
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Pamela Linford, Iván Pérez-Santos, Paulina Montero, Patricio A. Díaz, Claudia Aracena, Elías Pinilla, Facundo Barrera, Manuel Castillo, Aida Alvera-Azcárate, Mónica Alvarado, Gabriel Soto, Cécile Pujol, Camila Schwerter, Sara Arenas-Uribe, Pilar Navarro, Guido Mancilla-Gutiérrez, Robinson Altamirano, Javiera San Martín, and Camila Soto-Riquelme
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Georges Baaklini, Roy El Hourany, Milad Fakhri, Julien Brajard, Leila Issa, Gina Fifani, and Laurent Mortier
Ocean Sci., 18, 1491–1505, https://doi.org/10.5194/os-18-1491-2022, https://doi.org/10.5194/os-18-1491-2022, 2022
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We use machine learning to analyze the long-term variation of the surface currents in the Levantine Sea, located in the eastern Mediterranean Sea. We decompose the circulation into groups based on their physical characteristics and analyze their spatial and temporal variability. We show that most structures of the Levantine Sea are becoming more energetic over time, despite those of the western area remaining the most dominant due to their complex bathymetry and strong currents.
Alexander Barth, Aida Alvera-Azcárate, Charles Troupin, and Jean-Marie Beckers
Geosci. Model Dev., 15, 2183–2196, https://doi.org/10.5194/gmd-15-2183-2022, https://doi.org/10.5194/gmd-15-2183-2022, 2022
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Short summary
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Sylvain Watelet, Øystein Skagseth, Vidar S. Lien, Helge Sagen, Øivind Østensen, Viktor Ivshin, and Jean-Marie Beckers
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Ocean Sci. Discuss., https://doi.org/10.5194/os-2020-79, https://doi.org/10.5194/os-2020-79, 2020
Revised manuscript not accepted
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In this study, we use a numerical hindcast at high resolution (1/12°) to examine the occurrence and properties of Rossby waves in the North Atlantic between 1970–2015. We show evidence of Rossby waves travelling at 39° N at a speed of 4.17 cm s−1. These results are consistent with baroclinic Rossby waves generated by the North Atlantic Oscillation in the central North Atlantic and travelling westward before interacting with the Gulf Stream transport with a time lag of about 2 years.
Khalil Yala, N'Dèye Niang, Julien Brajard, Carlos Mejia, Mory Ouattara, Roy El Hourany, Michel Crépon, and Sylvie Thiria
Ocean Sci., 16, 513–533, https://doi.org/10.5194/os-16-513-2020, https://doi.org/10.5194/os-16-513-2020, 2020
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The paper is a contribution to the study of phytoplankton pigment climatology from satellite ocean-color observations in the Senegalo–Mauritanian upwelling, which is a very productive region where in situ observations are lacking. We processed the satellite data with an efficient new neural network classifier. We were able to provide the climatological cycle of diatoms. This study may have an economic impact on fisheries thanks to better knowledge of phytoplankton dynamics.
Alexander Barth, Aida Alvera-Azcárate, Matjaz Licer, and Jean-Marie Beckers
Geosci. Model Dev., 13, 1609–1622, https://doi.org/10.5194/gmd-13-1609-2020, https://doi.org/10.5194/gmd-13-1609-2020, 2020
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DINCAE is a method for reconstructing missing data in satellite datasets using a neural network. Satellite observations working in the optical and infrared bands are affected by clouds, which obscure part of the ocean underneath. In this paper, a neural network with the structure of a convolutional auto-encoder is developed to reconstruct the missing data based on the available cloud-free pixels in satellite images.
Marc Bocquet, Julien Brajard, Alberto Carrassi, and Laurent Bertino
Nonlin. Processes Geophys., 26, 143–162, https://doi.org/10.5194/npg-26-143-2019, https://doi.org/10.5194/npg-26-143-2019, 2019
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This paper describes an innovative way to use data assimilation to infer the dynamics of a physical system from its observation only. The method can operate with noisy and partial observation of the physical system. It acts as a deep learning technique specialised to dynamical models without the need for machine learning tools. The method is successfully tested on chaotic dynamical systems: the Lorenz-63, Lorenz-96, and Kuramoto–Sivashinski models and a two-scale Lorenz model.
Julien Brajard, Alberto Carrassi, Marc Bocquet, and Laurent Bertino
Geosci. Model Dev. Discuss., https://doi.org/10.5194/gmd-2019-136, https://doi.org/10.5194/gmd-2019-136, 2019
Revised manuscript not accepted
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We explore the possibility of combining data assimilation with machine learning. We introduce a new hybrid method for a two-fold scope: (i) emulating hidden, possibly chaotic, dynamics and (ii) predicting its future states. Numerical experiments have been carried out using the chaotic Lorenz 96 model, proving both the convergence of the hybrid method and its statistical skills including short-term forecasting and emulation of the long-term dynamics.
Luc Vandenbulcke and Alexander Barth
Ocean Sci., 15, 291–305, https://doi.org/10.5194/os-15-291-2019, https://doi.org/10.5194/os-15-291-2019, 2019
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In operational oceanography, regional and local models use large-scale models (such as those run by CMEMS) for their initial and/or boundary conditions, but unfortunately there is no feedback that improves the large-scale models. The present study aims at replacing normal two-way nesting by a data assimilation technique. This
upscalingmethod is tried out in the north-western Mediterranean Sea using the NEMO model and shows that the basin-scale model does indeed benefit from the nested model.
Charles Troupin, Ananda Pascual, Simon Ruiz, Antonio Olita, Benjamin Casas, Félix Margirier, Pierre-Marie Poulain, Giulio Notarstefano, Marc Torner, Juan Gabriel Fernández, Miquel Àngel Rújula, Cristian Muñoz, Eva Alou, Inmaculada Ruiz, Antonio Tovar-Sánchez, John T. Allen, Amala Mahadevan, and Joaquín Tintoré
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The AlborEX (the Alboran Sea Experiment) consisted of an experiment in the Alboran Sea (western Mediterranean Sea) that took place between 25 and 31 May 2014, and use a wide range of oceanographic sensors. The dataset provides information on mesoscale and sub-mesoscale processes taking place in a frontal area. This paper presents the measurements obtained from these sensors and describes their particularities: scale, spatial and temporal resolutions, measured variables, etc.
Athanasia Iona, Athanasios Theodorou, Sarantis Sofianos, Sylvain Watelet, Charles Troupin, and Jean-Marie Beckers
Earth Syst. Sci. Data, 10, 1829–1842, https://doi.org/10.5194/essd-10-1829-2018, https://doi.org/10.5194/essd-10-1829-2018, 2018
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The paper introduces a new product composed of a set of climatic indices from 1950 to 2015 for the Mediterranean Sea. It is produced from a high-resolution decadal climatology of temperature and salinity on a 1/8 degree regular grid based on the SeaDataNet V2 historical data collection. The climatic indices can contribute to the studies of the long-term variability of the Mediterranean Sea and the better understanding of the complex response of the region to the ongoing global climate change.
Athanasia Iona, Athanasios Theodorou, Sylvain Watelet, Charles Troupin, Jean-Marie Beckers, and Simona Simoncelli
Earth Syst. Sci. Data, 10, 1281–1300, https://doi.org/10.5194/essd-10-1281-2018, https://doi.org/10.5194/essd-10-1281-2018, 2018
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We compute a new, high-resolution hydrographic atlas for the Mediterranean Sea using the Data-Interpolating Variational Analysis technique and the latest SeaDataNet aggregated data collection in an effort to contribute to the studies of the long-term variability of the hydrological characteristics of the Mediterranean region and its climate change.
Hector Simon Benavides Pinjosovsky, Sylvie Thiria, Catherine Ottlé, Julien Brajard, Fouad Badran, and Pascal Maugis
Geosci. Model Dev., 10, 85–104, https://doi.org/10.5194/gmd-10-85-2017, https://doi.org/10.5194/gmd-10-85-2017, 2017
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The objective of this work is to deliver the adjoint model of SECHIBA obtained with software called YAO, in order to perform 4D-VAR data assimilation. The SECHIBA module of the ORCHIDEE land surface model describes the exchanges of water and energy between the surface and the atmosphere. A distributed version is available when only the land surface temperature is used as an observation, with two examples and documentation.
Marcos García Sotillo, Emilio Garcia-Ladona, Alejandro Orfila, Pablo Rodríguez-Rubio, José Cristobal Maraver, Daniel Conti, Elena Padorno, José Antonio Jiménez, Este Capó, Fernando Pérez, Juan Manuel Sayol, Francisco Javier de los Santos, Arancha Amo, Ana Rietz, Charles Troupin, Joaquín Tintore, and Enrique Álvarez-Fanjul
Earth Syst. Sci. Data, 8, 141–149, https://doi.org/10.5194/essd-8-141-2016, https://doi.org/10.5194/essd-8-141-2016, 2016
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An intensive drifter deployment was carried out in the Strait of Gibraltar: 35 satellite tracked drifters were released, coordinating to this aim 4 boats, covering an area of about 680 NM2 in 6 hours. This MEDESS-GIB Experiment is the most important exercise in the Mediterranean in terms of number of drifters released. The MEDESS-GIB dataset provides a complete Lagrangian view of the surface inflow of Atlantic waters through the Strait of Gibraltar and its later evolution along the Alboran Sea.
J.-M. Beckers, A. Barth, I. Tomazic, and A. Alvera-Azcárate
Ocean Sci., 10, 845–862, https://doi.org/10.5194/os-10-845-2014, https://doi.org/10.5194/os-10-845-2014, 2014
J. Marmain, A. Molcard, P. Forget, A. Barth, and Y. Ourmières
Nonlin. Processes Geophys., 21, 659–675, https://doi.org/10.5194/npg-21-659-2014, https://doi.org/10.5194/npg-21-659-2014, 2014
A. Barth, J.-M. Beckers, C. Troupin, A. Alvera-Azcárate, and L. Vandenbulcke
Geosci. Model Dev., 7, 225–241, https://doi.org/10.5194/gmd-7-225-2014, https://doi.org/10.5194/gmd-7-225-2014, 2014
Related subject area
Approach: Remote Sensing | Properties and processes: Coastal and near-shore processes
Surface circulation characterization along the middle southern coastal region of Vietnam from high-frequency radar and numerical modeling
A new airborne system for simultaneous high-resolution ocean vector current and wind mapping: first demonstration of the SeaSTAR mission concept in the macrotidal Iroise Sea
Drivers of Laptev Sea interannual variability in salinity and temperature
Thanh Huyen Tran, Alexei Sentchev, Thai To Duy, Marine Herrmann, Sylvain Ouillon, and Kim Cuong Nguyen
Ocean Sci., 21, 1–18, https://doi.org/10.5194/os-21-1-2025, https://doi.org/10.5194/os-21-1-2025, 2025
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For the first time, high-resolution surface current data from high-frequency radar have been obtained along the central and southern coasts of Vietnam, and combined with a modelling approach, this is helping scientists to understand coastal processes. The research showed that the surface circulation is driven not only by winds, but also by other factors. This can enrich public knowledge of the coastal dynamics that govern other environmental impacts along the coasts.
David L. McCann, Adrien C. H. Martin, Karlus A. C. de Macedo, Ruben Carrasco Alvarez, Jochen Horstmann, Louis Marié, José Márquez-Martínez, Marcos Portabella, Adriano Meta, Christine Gommenginger, Petronilo Martin-Iglesias, and Tania Casal
Ocean Sci., 20, 1109–1122, https://doi.org/10.5194/os-20-1109-2024, https://doi.org/10.5194/os-20-1109-2024, 2024
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This paper presents the results of the first scientific campaign of a new method to remotely sense the small-scale, fast-evolving dynamics that are vital to our understanding of coastal and shelf sea processes. This work represents the first demonstration of the simultaneous measurement of current and wind vectors from this novel method. Comparisons with other current measuring systems and models around the dynamic area of the Iroise Sea are presented and show excellent agreement.
Phoebe A. Hudson, Adrien C. H. Martin, Simon A. Josey, Alice Marzocchi, and Athanasios Angeloudis
Ocean Sci., 20, 341–367, https://doi.org/10.5194/os-20-341-2024, https://doi.org/10.5194/os-20-341-2024, 2024
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Satellite salinity data are used for the first time to study variability in Arctic freshwater transport from the Lena River and are shown to be a valuable tool for studying this region. These data confirm east/westerly wind is the main control on fresh water and sea ice transport rather than the volume of river runoff. The strong role of the wind suggests understanding how wind patterns will change is key to predicting future Arctic circulation and sea ice concentration.
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Short summary
Most satellite observations have gaps, for example, due to clouds. This paper presents a method to reconstruct missing data in satellite observations of the chlorophyll a concentration in the Black Sea. Rather than giving a single possible reconstructed field, the discussed method provides an ensemble of possible reconstructions using a generative neural network. The resulting ensemble is validated using techniques from numerical weather prediction and ocean modelling.
Most satellite observations have gaps, for example, due to clouds. This paper presents a method...
