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1. Probabilistic Models and Deep Learning Models Assessed to Estimate Design and Operational Ocean Wave Statistics to Reduce Coastal Hazards

Author

Mourani Sinha, Mrinmoyee Bhattacharya, M. Seemanth, and Suchandra A. Bhowmick

Subjects
deep learning, probability distributions, design wave parameters, operational wave parameters, numerical wave models, Indian Ocean, Geology, QE1-996.5
Abstract

Probabilistic models for long-term estimations and deep learning models for short-term predictions have been evaluated and analyzed for ocean wave parameters. Estimation of design and operational wave parameters for long-term return periods is essential for various coastal and ocean engineering applications. Three probability distributions, namely generalized extreme value distribution (EV), generalized Pareto distribution (PD), and Weibull distribution (WD), have been considered in this work. The design wave parameter considered is the maximal wave height for a specified return period, and the operational wave parameters are the mean maximal wave height and the highest occurring maximal wave height. For precise location-based estimation, wave heights are considered from a nested wave model, which has been configured to have a 10 km spatial resolution. As per availability, buoy-observed data are utilized for validation purposes at the Agatti, Digha, Gopalpur, and Ratnagiri stations along the Indian coasts. At the stations mentioned above, the long short-term memory (LSTM)-based deep learning model is applied to provide short-term predictions with higher accuracy. The probabilistic approach for long-term estimation and the deep learning model for short-term prediction can be used in combination to forecast wave statistics along the coasts, reducing hazards.

Published
2023
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2. The Benefits of the Ka-Band as Evidenced from the SARAL/AltiKa Altimetric Mission: Scientific Applications

Author

Jacques Verron, Pascal Bonnefond, Lofti Aouf, Florence Birol, Suchandra A. Bhowmick, Stéphane Calmant, Taina Conchy, Jean-François Crétaux, Gérald Dibarboure, A. K. Dubey, Yannice Faugère, Kevin Guerreiro, P. K. Gupta, Mathieu Hamon, Fatma Jebri, Raj Kumar, Rosemary Morrow, Ananda Pascual, Marie-Isabelle Pujol, Elisabeth Rémy, Frédérique Rémy, Walter H. F. Smith, Jean Tournadre, and Oscar Vergara

Subjects
altimetry, Ka-band, oceanography, hydrology, ice, geodesy, Science
Abstract

The India–France SARAL/AltiKa mission is the first Ka-band altimetric mission dedicated primarily to oceanography. The mission objectives were firstly the observation of the oceanic mesoscales but also global and regional sea level monitoring, including the coastal zone, data assimilation, and operational oceanography. SARAL/AltiKa proved also to be a great opportunity for inland waters applications, for observing ice sheet or icebergs, as well as for geodetic investigations. The mission ended its nominal phase after three years in orbit and began a new phase (drifting orbit) in July 2016. The objective of this paper is to highlight some of the most remarkable achievements of the SARAL/AltiKa mission in terms of scientific applications. Compared to the standard Ku-band altimetry measurements, the Ka-band provides substantial improvements in terms of spatial resolution and data accuracy. We show here that this leads to remarkable advances in terms of observation of the mesoscale and coastal ocean, waves, river water levels, ice sheets, icebergs, fine scale bathymetry features as well as for the many related applications.

Published
2018
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4. Generation of Non-Linear Technique Based 6 Hourly Wind Reanalysis Products Using SCATSAT-1 and Numerical Weather Prediction Model Outputs

Author

Suchandra Aich Bhowmick, Maneesha Gupta, Abhisek Chakraborty, Neeraj Agarwal, Rashmi Sharma, and Meer Mohammed Ali

Subjects
winds, SCATSAT-1, NCMRWF (National Center for Medium Range Weather Forecasting), CCMP (Cross Calibrated Multi-Platform), particle filter, Science
Abstract

We combined observations of ocean surface winds from Indian SCATterometer SATellite-1 (SCATSAT-1) with a background wind field from a numerical weather prediction (NWP) model available at National Centre for Medium-Range Weather Forecast (NCMRWF) to generate a 6-hourly gridded hybrid wind product. A distinctive feature of the study is to produce a global gridded wind field from SCATSAT-1 scatterometer passes with spatio-temporal data gaps at regular synoptic hours relevant for forcing models and other NWP studies. We are following the concept from the modern particle filter technique, which does not represent the model probability density function (PDF) as Gaussian. We generated the 6-hourly hybrid winds for 2018 and validated them using the wind speed from daily gridded level-4 SCATSAT-1 winds (L4AW), Cross Calibrated Multi-Platform (CCMP) dataset and global buoy data from National Data Buoy Centre (NDBC). The results suggest the potential of the technique to produce scatterometer winds at the desired temporal frequency with significantly less noise and bias along the swath. The study shows that the generated hybrid winds are of prime quality compared with the already existing daily products available from Indian Space Research Organization (ISRO).

Published
2023
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5. Altimetry for the Future: Building on 25 Years of Progress

Author

Saleh Abdalla, Abdolnabi Abdeh Kolahchi, Susheel Adusumilli, Suchandra Aich Bhowmick, Eva Alou-Font, Laiba Amarouche, Ole Baltazar Andersen, Helena Antich, Lotfi Aouf, Brian Arbic, Thomas Armitage, Sabine Arnault, Camila Artana, Giuseppe Aulicino, Nadia Ayoub, Sergei Badulin, Steven Baker, Chris Banks, Lifeng Bao, Silvia Barbetta, Barbara Barcelo-Llull, Francois Barlier, Sujit Basu, Peter Bauer-Gottwein, Matthias Becker, Brian Beckley, Nicole Bellefond, Tatyana Belonenko, Mounir Benkiran, Touati Benkouider, Ralf Bennartz, Jerome Benveniste, Nicolas Bercher, Muriel Berge-Nguyen, Joao Bettencourt, Fabien Blarel, Alejandro Blazquez, Denis Blumstein, Pascal Bonnefond, Franck Borde, Jerome Bouffard, Francois Boy, Jean-Paul Boy, Cedric Brachet, Pierre Brasseur, Alexander Braun, Luca Brocca, David Brockley, Laurent Brodeau, Shannon Brown, Sean Bruinsma, Anna Bulczak, Sammie Buzzard, Madeleine Cahill, Stephane Calmant, Michel Calzas, Stefania Camici, Mathilde Cancet, Hugues Capdeville, Claudia Cristina Carabajal, Loren Carrere, Anny Cazenave, Eric P. Chassignet, Prakash Chauhan, Selma Cherchali, Teresa Chereskin, Cecile Cheymol, Daniele Ciani, Paolo Cipollini, Francesca Cirillo, Emmanuel Cosme, Steve Coss, Yuri Cotroneo, David Cotton, Alexandre Couhert, Sophie Coutin-Faye, Jean-Francois Cretaux, Frederic Cyr, Francesco d’Ovidio, Jose Darrozes, Cedric David, Nadim Dayoub, Danielle De Staerke, Xiaoli Deng, Shailen Desai, Jean-Damien Desjonqueres, Denise Dettmering, Alessandro Di Bella, Lara Dıaz-Barroso, Gerald Dibarboure, Habib Boubacar Dieng, Salvatore Dinardo, Henryk Dobslaw, Guillaume Dodet, Andrea Doglioli, Alessio Domeneghetti, David Donahue, Shenfu Dong, Craig Donlon, Joel Dorandeu, Christine Drezen, Mark Drinkwater, Yves Du Penhoat, Brian Dushaw, Alejandro Egido, Svetlana Erofeeva, Philippe Escudier, Saskia Esselborn, Pierre Exertier, Ronan Fablet, Cedric Falco, Sinead Louise Farrell, Yannice Faugere, Pierre Femenias, Luciana Fenoglio, Joana Fernandes, Juan Gabriel Fernandez, Pascale Ferrage, Ramiro Ferrari, Lionel Fichen, Paolo Filippucci, Stylianos Flampouris, Sara Fleury, Marco Fornari, Rene Forsberg, Frederic Frappart, Marie-laure Frery, Pablo Garcia, Albert Garcia-Mondejar, Julia Gaudelli, Augusto Getirana, Lucile Gaultier, Ferran Gibert, Artur Gil, Lin Gilbert, Sarah Gille, Luisella Giulicchi, Jesus Gomez-Enri, Laura Gomez-Navarro, Christine Gommenginger, Lionel Gourdeau, David Griffin, Andreas Groh, Alexandre Guerin, Raul Guerrero, Thierry Guinle, Praveen Gupta, Benjamin D. Gutknecht, Mathieu Hamon, Guoqi Han, Daniele Hauser, Veit Helm, Stefan Hendricks, Fabrice Hernandez, Anna Hogg, Martin Horwath, Martina Idzanovic, Peter Janssen, Eric Jeansou, Yongjun Jia, Yuanyuan Jia, Liguang Jiang, Johnny A. Johannessen, Masafumi Kamachi, Svetlana Karimova, Kathryn Kelly, Sung Yong Kim, Robert King, Cecile M.M. Kittel, Patrice Klein, Anna Klos, Per Knudsen, Rolf Koenig, Andrey Kostianoy, Alexei Kouraev, Raj Kumar, Sylvie Labroue, Loreley Selene Lago, Juliette Lambin, Lea Lasson, Olivier Laurain, Remi Laxenaire, Clara Lazaro, Sophie Le Gac, Julien Le Sommer, Pierre-Yves Le Traon, Sergey Lebedev, Fabien Leger, Benoit Legresy, Frank Lemoine, Luc Lenain, Eric Leuliette, Marina Levy, John Lillibridge, Jianqiang Liu, William Llovel, Florent Lyard, Claire Macintosh, Eduard Makhoul Varona, Cécile Manfredi, Frédéric Marin, Evan Mason, Christian Massari, Constantin Mavrocordatos, Nikolai Maximenko, Malcolm McMillan, Thierry Medina, Angelique Melet, Marco Meloni, Stelios Mertikas, Sammy Metref, Benoit Meyssignac, Jean-François Minster, Thomas Moreau, Daniel Moreira, Yves Morel, Rosemary Morrow, John Moyard, Sandrine Mulet, Marc Naeije, Robert Steven Nerem, Hans Ngodock, Karina Nielsen, Jan Even Øie Nilsen, Fernando Niño, Carolina Nogueira Loddo, Camille Noûs, Estelle Obligis, Inès Otosaka, Michiel Otten, Berguzar Oztunali Ozbahceci, Roshin P. Raj, Rodrigo Paiva, Guillermina Paniagua, Fernando Paolo, Adrien Paris, Ananda Pascual, Marcello Passaro, Stephan Paul, Tamlin Pavelsky, Christopher Pearson, Thierry Penduff, Fukai Peng, Felix Perosanz, Nicolas Picot, Fanny Piras, Valerio Poggiali, Étienne Poirier, Sonia Ponce de León, Sergey Prants, Catherine Prigent, Christine Provost, M-Isabelle Pujol, Bo Qiu, Yves Quilfen, Ali Rami, R. Keith Raney, Matthias Raynal, Elisabeth Remy, Frédérique Rémy, Marco Restano, Annie Richardson, Donald Richardson, Robert Ricker, Martina Ricko, Eero Rinne, Stine Kildegaard Rose, Vinca Rosmorduc, Sergei Rudenko, Simón Ruiz, Barbara J. Ryan, Corinne Salaün, Antonio Sanchez-Roman, Louise Sandberg Sørensen, David Sandwell, Martin Saraceno, Michele Scagliola, Philippe Schaeffer, Martin G. Scharffenberg, Remko Scharroo, Andreas Schiller, Raphael Schneider, Christian Schwatke, Andrea Scozzari, Enrico Ser-giacomi, Frederique Seyler, Rashmi Shah, Rashmi Sharma, Andrew Shaw, Andrew Shepherd, Jay Shriver, C.K. Shum, Wim Simons, Sebatian B. Simonsen, Thomas Slater, Walter Smith, Saulo Soares, Mikhail Sokolovskiy, Laurent Soudarin, Ciprian Spatar, Sabrina Speich, Margaret Srinivasan, Meric Srokosz, Emil Stanev, Joanna Staneva, Nathalie Steunou, Julienne Stroeve, Bob Su, Yohanes Budi Sulistioadi, Debadatta Swain, Annick Sylvestre-baron, Nicolas Taburet, Rémi Tailleux, Katsumi Takayama, Byron Tapley, Angelica Tarpanelli, Gilles Tavernier, Laurent Testut, Praveen K. Thakur, Pierre Thibaut, LuAnne Thompson, Joaquín Tintoré, Céline Tison, Cédric Tourain, Jean Tournadre, Bill Townsend, Ngan Tran, Sébastien Trilles, Michel Tsamados, Kuo-Hsin Tseng, Clément Ubelmann, Bernd Uebbing, Oscar Vergara, Jacques Verron, Telmo Vieira, Stefano Vignudelli, Nadya Vinogradova Shiffer, Pieter Visser, Frederic Vivier, Denis Volkov, Karina von Schuckmann, Valerii Vuglinskii, Pierrik Vuilleumier, Blake Walter, Jida Wang, Chao Wang, Christopher Watson, John Wilkin, Josh Willis, Hilary Wilson, Philip Woodworth, Kehan Yang, Fangfang Yao, Raymond Zaharia, Elena Zakharova, Edward D. Zaron, Yongsheng Zhang, Zhongxiang Zhao, Vadim Zinchenko, and Victor Zlotnicki

Subjects
Space Sciences (General), Geosciences (General)
Abstract

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.

Published
2021
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7. Monsoonal Variability in the Mesoscale Coupling of Wind and SST in the Arabian Sea

Author

Suchandra Aich Bhowmick, Smitha Ratheesh, Aditya Chaudhary, and Neeraj Agarwal

Subjects
Geophysics, Coupling (computer programming), Geochemistry and Petrology, Climatology, Mesoscale meteorology, Wind stress, Environmental science, Seawater, Scatterometer, Monsoon, Wind speed, Coupling coefficient of resonators
Abstract

Satellite observations over the Arabian Sea (AS) have revealed a strong signature of air–sea interaction during the Indian Ocean monsoon. In this study, satellite observations of ocean surface winds from the SCATSAT scatterometer are used to study the monsoonal variability in wind and SST (WS) coupling over the AS at the oceanic mesoscale for the period 2017 to 2019. The study investigates the role of critical parameters including SST gradient, wind speed steadiness and wind directional steadiness with respect to coupling during the winter and summer monsoons. Mesoscale WS coupling is stronger in the summer monsoon. A seasonally varying threshold of SST gradient required for the generation of WS coupling is clearly visible. This threshold is higher during the summer monsoon (0.8 °C/100 km) than during the winter monsoon (0.4 °C/100 km). Results reveal the need for a strong background wind field along with SST gradient for the generation of strong WS coupling. While a strong SST gradient (> 0.8 °C/100 km) is sufficient to overcome the adverse influence of background wind conditions, strong support from the stable background wind fields is necessary in the regions with a relatively weak SST gradient (> 0.4 °C/100 km) for the generation of coupling. The observed coupling between the SST and wind is quantified using a coupling coefficient. The coupling between wind stress divergence and downwind SST gradient is more prominent. It is observed that large warming of seawater (SST anomaly > 1 °C) suppressed the positive linear coupling between anomalies of wind speed and SST in the western AS during the summer monsoon.

Published
2021

8. A Pathway for Multi-Stage Cyclone-Induced Hazard Tracking – Case Study for Yaas

Author

Atul Kumar Varma, Neeru Jaiswal, Ayan Das, Mukesh Kumar, Nikhil V. Lele, Rojalin Tripathy, Saroj Maity, Mehul Pandya, Bimal Bhattacharya, Anup Kumar Mandal, M. Jishad, M. Seemanth, Arvind Sahay, Debojyoti Ganguly, Suchandra Aich Bhowmick, R.K. Sarangi, Neeraj Agarwal, Mini Raman, Rashmi Sharma, Vibhuti Bhushan Jha, Nimisha Singh, Rohit Pradhan, Amit K. Dubey, Shard Chander, R.P. Singh, Neerja Sharma, Shivani Shah, Ishmohan Bahuguna, and Nilesh M. Desai

Abstract

A Very Severe Cyclonic Storm “Yaas” developed over the Bay of Bengal (BoB) on May 23, 2021, and crossed over the Odisha coast on May 26 with maximum sustained wind speed of 75 kts. Herein, a pathway has been developed and exemplified for ‘Yaas’ through three-stage cyclone-induced hazard tracking. Days before the cyclone formation, Cyclone Genesis Potential Parameter, Sea Surface Temperature (SST) (> 30 0C) and Tropical Cyclone Heat Potential (anomaly of 40–80 kJ/cm2) indicated a strong possibility of cyclogenesis in the BoB. A Lagrangian Advection Model used for its track prediction with 24-hour lead-time provided an accuracy of ~ 19 km and ~ 6 hour in its landfall location and time. Further, intensity prediction was done using Numerical Weather Prediction model. Geostationary Satellites, INSAT-3D/3DR, were used to visualise cyclone structure. Passing of cyclone had its reverbarations in oceans, which are observed in SST drop of ~ 3o C, salinity and density increase by ~ 1 psu and ~ 2 Kg/m3, respectively. During the period, 23–26 May 2021, the Ekman suction velocity and chlorophyll concentration were found significantly high at ~ 5m/day and > 0.5 mg/m3, respectively. Forecast of storm surge was found to be between 3.5-4 m at coastal locations. Significant wave height was found to be 5.5 to 9.2 m. The coastal inundation forecast for 24 May 2021 provided its quantitative maximum inland extent. Finally, loss of the crop, fishery and forest areas by strong winds and inundation/ingress of saline water associated with storm surge were examined using SAR and optical data.

Published
2022

9. The Indian Contribution to the CEOS-VC

Author

Devang Mankad, Abhisek Chakraborty, Suchandra Aich Bhowmick, Prantik Chakraborty, and Raj Kumar

Subjects
Spaceborne radar, Data products, Meteorology, Payload, Satellite data, Environmental science, Scatterometer, Space research, Space exploration
Abstract

Indian Space Research Organization (ISRO) has started contributing towards international tandem space-borne scatterometer missions by successfully launching a Ku-band pencil-beam scatterometer onboard Oceansat-2 in September 2009. The Oceansat-2 scatterometer (OSCAT) continued to provide good quality observations of ocean surface vector winds till February 2014, when a major power failure ceased the mission. In September 2016, ISRO launched another Ku-band scatterometer as a sole payload onboard Scatsat-1. The Scatsat-1 followed the design heritage of OSCAT with some improved configuration. After the initial CAL/VAL phase, the Scatsat-1was to found to provide excellent quality of wind products. The present status of Scatsat-1 is operational. The operational data products from Scatsat-1 as well as archived products from OSCAT are available from both National Remote Sensing Centre (NRSC, www.nrsc.gov.in) and Meteorological and Oceanographic Satellite Data Archival Centre (MOSDAC, www.mosdac.gov.in). Apart from the operational products from these scatterometers, there are several other value added products are routinely generated and disseminated from MOSDAC. Table-1 shows the brief descriptions of the operational and value added products available from Scatsat-1.

Published
2021

10. The SARAL/AltiKa mission: A step forward to the future of altimetry

Author

Lionel Gourdeau, Pascal Bonnefond, Sara Fleury, David T. Sandwell, Jean-François Crétaux, Mei Ling Dabat, Ole Baltazar Andersen, Jacques Verron, Gérald Dibarboure, Denis Blumstein, Fabrice Ardhuin, François Boy, Karen M. Marks, Florent Garnier, Nadège Queruel, Laurent Brodeau, Suchandra Aich Bhowmick, Walter H. F. Smith, Muriel Berge-Nguyen, Edward D. Zaron, Observatoire de Paris, Université Paris sciences et lettres (PSL), Laboratoire d'Océanographie Physique et Spatiale (LOPS), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), and Centre National d'Études Spatiales [Toulouse] (CNES)

Subjects
Atmospheric Science, 010504 meteorology & atmospheric sciences, Meteorology, Aerospace Engineering, 01 natural sciences, Reaction wheel, Footprint, 0103 physical sciences, Ka band, Altimeter, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Constellation, Horizontal resolution, Astronomy and Astrophysics, Ka-band, Geophysics, [SDU]Sciences of the Universe [physics], 13. Climate action, Space and Planetary Science, Satellite, Orbit (dynamics), General Earth and Planetary Sciences, Environmental science, Altimetry
Abstract

International audience; The CNES/ISRO altimetric satellite SARAL/AltiKa was launched in February 2013 and since then has provided useful data for various scientific and operational applications in oceanography, hydrology, cryospheric sciences and geodesy. However, a Reaction Wheel problem forced relaxation of the repeatability constraint on the satellite's orbit, which has been drifting slowly since July 2016. Beyond the expected contributions of this mission and its very good integration into the objectives of the constellation of altimetric satellites, it has become more and more apparent that specific contributions and innovations related to the main specification of SARAL/AltiKa, that is to say the use of the Ka-band, have clearly emerged. The advantages of the Ka-band are in short the reduction of ionosphere effects, the smaller footprint, the better horizontal resolution and the higher vertical resolution. A drawback of the Ka-band is the attenuation due to water/water vapor in case of rain and the resulting loss of data. The main objective of this paper is to highlight the specific advances of the Ka-band in different scientific and technical fields and to show why they are promising for the future and open the way to several missions or mission projects. Although unplanned initially, the fine coverage of the Drifting Phase brings some interesting openings especially for geodesy and hydrology applications.

Published
2021

11. A Simplified Assimilation Scheme for a Coastal Wave Model Using Concepts of Particle Filter

Author

Suchandra Aich Bhowmick, Smitha Ratheesh, Raj Kumar, Sujit Basu, and Rashmi Sharma

Subjects
Meteorology, Gaussian, Probability density function, 010502 geochemistry & geophysics, 01 natural sciences, Physics::Geophysics, Wave model, symbols.namesake, Geophysics, Bootstrapping (electronics), Geochemistry and Petrology, Resampling, symbols, Environmental science, Altimeter, Particle filter, Significant wave height, Physics::Atmospheric and Oceanic Physics, 0105 earth and related environmental sciences
Abstract

In this work, observations of ocean wave height from satellite altimeters are assimilated into the coastal wave model simulating waves nearshore (SWAN) operating in the Indian coastal waters. The study has two distinctive features. The most important is the use of certain concepts of the modern particle filter technique, which does not represent the model probability density function (PDF) by a Gaussian. The other feature is the joint assimilation of data from three altimeters. The method starts by generating an initial ensemble by the bootstrap technique in which the significant wave height (SWH) field of a control run is perturbed by randomly adding bias to produce a member of the ensemble. At the first assimilation time, a weight-based resampling of the individual members, known as particles, is performed. Stronger particles are retained, while the weaker ones are discarded. In order to keep the ensemble size constant, the algorithm replicates a few strong members. After this resampling, a single model run is employed in the forecast step using a kind of averaging. At the next assimilation time, a synthetic ensemble is again formed by the same bootstrapping, and observations are assimilated. The forecast–assimilation cycle is repeated until the observations are exhausted. Assimilation experiments were conducted for 6 months from February through July in 2016. The power of the technique is evaluated by validating results with altimeter data as well as independent data sets from moored buoys. The results are found to be extremely encouraging for the use of this method in carrying out coastal wave forecasting.

Published
2019

12. Implementation of altimeter data assimilation on a regional wave forecasting system and its impact on wave and swell surge forecast in the Indian Ocean

Author

Arun Chakraborty, Suchandra Aich Bhowmick, T. M. Balakrishnan Nair, Rashmi Sharma, Raj Kumar, P. G. Remya, and M. Seemanth

Subjects
Environmental Engineering, Data assimilation, Buoy, Meteorology, Forecast period, Environmental science, Ocean Engineering, Altimeter, Surge, Significant wave height, Lead time, Swell
Abstract

In the present work, we have operationally implemented a data assimilation (DA) scheme in the wave forecasting system at the Indian operational agency, Indian National Centre for Ocean Information Services (INCOIS). Significant Wave Height (SWH) measurements from the SARAL/AltiKa, Jason-2 and Jason-3 altimeters were assimilated using the Optimal Interpolation technique. The impact of altimeter DA towards improving the reliability of wave predictions in the Indian Ocean is evaluated by validating the forecasted wave parameters with buoy observations. The assimilation of altimeter data showed considerable improvement in the wave predictions. SWH forecast in the northern Indian Ocean region improved up to ~15 % in the first 24 h period. The improvement in forecasted wave parameters were due to the correction in swell forecast, which persists throughout the forecast period. For wind-sea forecast, impact of DA was less visible (~4–6% improvement up to forecast lead time of 24 h), as it is primarily driven by local wind fields. The positive impact of DA on the swell forecast is further established considering a swell surge event, named Kallakkadal.

Published
2021

13. Role of ocean heat content in boosting post-monsoon tropical storms over Bay of Bengal during La-Niña events

Author

Rashmi Sharma, M. M. Ali, Neeraj Agarwal, C. M. Kishtawal, and Suchandra Aich Bhowmick

Subjects
Atmospheric Science, 010504 meteorology & atmospheric sciences, Subtropical Indian Ocean Dipole, Physical oceanography, 010502 geochemistry & geophysics, Monsoon, 01 natural sciences, Sea surface temperature, Oceanography, Climatology, Thermohaline circulation, Indian Ocean Dipole, Ocean heat content, Tropical cyclone, Geology, 0105 earth and related environmental sciences
Abstract

This study aims to analyze the role of ocean heat content in boosting the post-monsoon cyclonic activities over Bay of Bengal during La-Nina events. In strong La-Nina years, accumulated cyclone energy in Bay of Bengal is much more as compared to any other year. It is observed that during late June to October of moderate to strong La-Nina years, western Pacific is warmer. Sea surface temperature anomaly of western Pacific Ocean clearly indicates the presence of relatively warmer water mass in the channel connecting the Indian Ocean and Pacific Ocean, situated above Australia. Ocean currents transport the heat zonally from Pacific to South eastern Indian Ocean. Excess heat of the southern Indian Ocean is eventually transported to eastern equatorial Indian Ocean through strong geostrophic component of ocean current. By September the northward transport of this excess heat from eastern equatorial Indian Ocean to Bay of Bengal takes place during La-Nina years boosting the cyclonic activities thereafter.

Published
2016

14. Sensitivity analysis of dissipation parameterizations in a third-generation spectral wave model, WAVEWATCH III for Indian Ocean

Author

Raj Kumar, Suchandra Aich Bhowmick, M. Seemanth, and Rashmi Sharma

Subjects
Source function, Environmental Engineering, 010504 meteorology & atmospheric sciences, Buoy, 010505 oceanography, Ocean Engineering, Dissipation, Monsoon, Atmospheric sciences, 01 natural sciences, Swell, Wave model, Environmental science, Altimeter, Tropical cyclone, 0105 earth and related environmental sciences
Abstract

Present study determines sensitivity of different input and dissipation parameterization schemes available in a third-generation wind-wave model, WAVEWATCH III for Indian Ocean (IO), using collocated altimeter and in-situ buoy measurements. For IO, in general, parameterization by Bidlot et al. (2005, referred as BAJ) is found to be the best in simulating SWH, for all the seasons. Albeit NIO is a part of IO, wave climate over this region is different as it exhibits variability in surface wind conditions before, after and during the monsoon phase. Thus, over NIO during pre- and post- monsoon seasons, when the region is dominated by swells propagating from the south, KC (KC denotes Kahma and Calkoen (1992, 1994)) stable parameterization scheme of Tolman and Chalikov (1996) is the better option for input and dissipation source function. During monsoon season, waves over NIO is primarily influenced by strong and persistent southwest monsoonal winds and dominated by young wind seas. BAJ parameterization is suggested as the better option during this phase. To simulate the high waves induced by tropical cyclones, KC stable parameterization of Tolman and Chalikov (1996) is found suitable.

Published
2016

15. Retrieval of Wind Stress at the Ocean Surface From AltiKa Measurements

Author

Mark A. Bourassa, Suchandra Aich Bhowmick, M. M. Ali, K. Niharika, and Rashmi Sharma

Subjects
Radiometer, 010504 meteorology & atmospheric sciences, Meteorology, Ocean current, 0211 other engineering and technologies, Wind stress, 02 engineering and technology, Geotechnical Engineering and Engineering Geology, 01 natural sciences, Standard deviation, Wind speed, Atmosphere, Sea surface temperature, Physics::Space Physics, Environmental science, Altimeter, Electrical and Electronic Engineering, Physics::Atmospheric and Oceanic Physics, 021101 geological & geomatics engineering, 0105 earth and related environmental sciences, Remote sensing
Abstract

Wind stress is an important parameter in generating the ocean surface currents. Here, for the first time, we directly estimate this parameter at the ocean surface using all the observations from AltiKa and the accompanying radiometer that affect the wind stress estimates and radar signal propagation through the atmosphere. For this purpose, we used an artificial neural network approach using in situ estimates as the dependent parameter and satellite records as the independent parameters. In the absence of sufficient in situ measurements, wind stress is generally inferred from wind speed at 10-m height obtained from spaceborne scatterometers and altimeters which has been extrapolated to the surface to estimate stress, assuming certain atmospheric conditions that are rarely correct. Hence, we obtained this parameter directly at the ocean surface from satellite records. The estimates for the independent validation data set have a standard deviation of the difference between the in situ and satellite-derived values of 0.032 Nm−2 with Pearson's correlation coefficient of 0.96 significant at 99% confidence level.

Published
2016

16. Impact of Assimilating SARAL/AltiKa SWH in SWAN Model During Indian Ocean Tropical Cyclone Phailin

Author

Rashmi Sharma, Raj Kumar, Suchandra Aich Bhowmick, and Sujit Basu

Subjects
010504 meteorology & atmospheric sciences, Meteorology, Buoy, 010502 geochemistry & geophysics, 01 natural sciences, Wave model, Data assimilation, Climatology, Wind wave, General Earth and Planetary Sciences, Environmental science, Cyclone, Altimeter, Electrical and Electronic Engineering, Tropical cyclone, Significant wave height, 0105 earth and related environmental sciences
Abstract

The focus of the study is assimilation of significant wave height (SWH) obtained from first Ka-band altimeter AltiKa onboard SARAL, a collaborative mission of the Indian Space Research Organization and Centre National d'Etudes Spatiales, France. The state-of-the art coastal wave model simulating waves near-shore has been used for this purpose. The well-tested optimal interpolation technique is adopted for this assimilation. A distinguishing feature of this study is the test of this assimilation scheme with SARAL/AltiKa data during the occurrence of a recent severe Cyclone Phailin in the Indian Ocean with its associated extreme waves. Before proceeding to assimilation per se, SARAL/AltiKa SWH has been validated using in situ as well as other satellite data. Apart from validation, this intercomparison also served the purpose of providing the needed error covariance to be used in assimilation. The supremacy of an assimilation run over a parallel control run without assimilation has been judged by comparing the results with Indian Ocean buoy observations and also with Jason-2 observations. The statistics of the validation of the assimilation run has been found to be extremely encouraging.

Published
2016

18. Estimation of Technical Wave Energy Potential in Exclusive Economic Zone of India

Author

Surendra Singh Kachhwaha, Abhinaya Srinivas Bhasuru, Garlapati Nagababu, Ravi Patel, Suchandra Aich Bhowmick, V. V. Arun Kumar Surisetty, and Seemanth Moideenkunju

Subjects
Shore, Estimation, Wave energy converter, geography, geography.geographical_feature_category, Environmental science, Exclusive economic zone, Energy (signal processing), Marine engineering
Abstract

Identification of the best location for wave farm installation, wave resource assessment needs to be carried out. In the present work, wave resource assessment along the Indian EEZ was carried out using the 17-year (2000 to 2016) output simulation of the third generation wave model WAVEWATCH-III (WWIII). Spatial distribution of significant wave height, mean wave energy period and annual mean of wave power is plotted. Further, the monthly and seasonal variation has been carried out to assess the effect on temporal variability at a specific location. The results show the annual mean wave power is in the range of 1–12 kW/m across the Indian EEZ. Further, it was observed that wave power along the western coast of India is more energetic than the eastern coast of India, with annual average wave power of 8–12 kW/m and 2–6 kW/m respectively. However, coastlines of Gujarat and Maharashtra experience the maximum seasonal and monthly variability across Indian EEZ, which is 2 and 3.5 respectively. By using different wave energy converters (WEC), the capacity factor and technical wave energy potential over the study area are estimated. Oceantec WEC shows maximum capacity factor (0.35) among the all selected wave energy converters. The results reveal that the electric wave power generation is 3 times more in the western coastal region as compared to the eastern coast of India.

Published
2018

19. The Benefits of the Ka-Band as Evidenced from the SARAL/AltiKa Altimetric Mission: Scientific Applications

Author

Yannice Faugère, Rosemary Morrow, Florence Birol, Marie-Isabelle Pujol, Ananda Pascual, Raj Kumar, Stéphane Calmant, Oscar Vergara, Lofti Aouf, Walter H. F. Smith, Frédérique Rémy, Mathieu Hamon, Pascal Bonnefond, Amit Dubey, Kevin Guerreiro, Elisabeth Remy, Gérald Dibarboure, Suchandra Aich Bhowmick, Jean Tournadre, Fatma Jebri, Jean-François Crétaux, Taina Conchy, P. K. Gupta, Jacques Verron, Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA), Systèmes de Référence Temps Espace (SYRTE), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Météo France, Echanges Côte-Large (ECOLA), Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Fluides, automatique, systèmes thermiques (FAST), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Collecte Localisation Satellites (CLS), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Centre National d'Études Spatiales [Toulouse] (CNES), Ultracold Atoms and Plasmas, Rice University [Houston], Laboratoire d'Océanographie Spatiale (LOS), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Institut méditerranéen d'océanologie (MIO), Centre National de la Recherche Scientifique (CNRS)-Université de Toulon (UTLN)-Aix Marseille Université (AMU)-Institut de Recherche pour le Développement (IRD), Centre de Recherche Paul Pascal (CRPP), Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS), Océan du Large et Variabilité Climatique (OLVAC), Institut Mediterrani d'Estudis Avancats (IMEDEA), Consejo Superior de Investigaciones Científicas [Spain] (CSIC)-Universidad de las Islas Baleares (UIB), Sciences pour l'Action et le Développement : Activités, Produits, Territoires (SADAPT), Institut National de la Recherche Agronomique (INRA)-AgroParisTech, Institut de Recherche pour le Développement (IRD)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Météo-France Direction Interrégionale Sud-Est (DIRSE), Météo-France, Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Toulon (UTLN)-Centre National de la Recherche Scientifique (CNRS), Université de Bordeaux (UB)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC)-Universidad de las Islas Baleares (UIB), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut de Recherche pour le Développement (IRD)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), and Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)

Subjects
010504 meteorology & atmospheric sciences, Meteorology, Science, Mesoscale meteorology, ice, hydrology, 010502 geochemistry & geophysics, 01 natural sciences, Data assimilation, altimetry, geodesy, Bathymetry, Ka band, 14. Life underwater, Altimeter, oceanography, Sea level, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, [PHYS]Physics [physics], geography, geography.geographical_feature_category, Iceberg, Ka-band, 13. Climate action, General Earth and Planetary Sciences, Ice sheet, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Geology
Abstract

International audience; The India-France SARAL/AltiKa mission is the first Ka-band altimetric mission dedicated primarily to oceanography. The mission objectives were firstly the observation of the oceanic mesoscales but also global and regional sea level monitoring, including the coastal zone, data assimilation, and operational oceanography. SARAL/AltiKa proved also to be a great opportunity for inland waters applications, for observing ice sheet or icebergs, as well as for geodetic investigations. The mission ended its nominal phase after three years in orbit and began a new phase (drifting orbit) in July 2016. The objective of this paper is to highlight some of the most remarkable achievements of the SARAL/AltiKa mission in terms of scientific applications. Compared to the standard Ku-band altimetry measurements, the Ka-band provides substantial improvements in terms of spatial resolution and data accuracy. We show here that this leads to remarkable advances in terms of observation of the mesoscale and coastal ocean, waves, river water levels, ice sheets, icebergs, fine scale bathymetry features as well as for the many related applications.

Published
2018

20. An Artificial Neural Network Model Function (AMF) for SARAL-Altika Winds

Author

Rashmi Sharma, I. Venkata Ramana, M. M. Ali, K. Niharika, Aditya Chaudhury, Mark A. Bourassa, John C. Pezzullo, and Suchandra Aich Bhowmick

Subjects
Atmospheric Science, Meteorology, Backscatter, Wind speed, law.invention, Atmosphere, law, Physics::Space Physics, Environmental science, Waveform, Satellite, Altimeter, Computers in Earth Sciences, Radar, Significant wave height, Physics::Atmospheric and Oceanic Physics, Remote sensing
Abstract

High-quality winds over the ocean surface, at an enhanced spatio-temporal resolution are required for a better understanding of the dynamics of the ocean and atmosphere. Altimetry helps in increasing the frequency of satellite observations. Traditional algorithms for wind speed retrievals from altimeter consider only the backscatter (sigma-0) and possibly the significant wave height (SWH). In this study, we propose an artificial neural network (ANN) model function for AltiKa on board Satellite for ARgos and ALtiKa (SARAL) to relate wind speed to sigma-0, SWH, the width of the waveform leading edge, the two brightness temperatures (TBK and TBKa), and the amplitude of the 1-Hz echo. These parameters influence either the backscatter from the ocean or the propagation of the altimeter radar signal. The wind estimates have significantly improved by incorporating these parameters.

Published
2015

21. Analysis of SARAL/AltiKa Wind and Wave over Indian Ocean and its Real-time Application in Wave Forecasting System at ISRO

Author

M. Seemanth, Ruchi Modi, Suchandra Aich Bhowmick, T. M. Balakrishnan Nair, K. G. Sandhya, Rashmi Sharma, and Raj Kumar

Subjects
Shore, geography, Wave model, Indian ocean, geography.geographical_feature_category, Meteorology, Altimeter, Covariance, Oceanography, Significant wave height, Space research, Remote sensing, Interpolation
Abstract

The current study aims to analyze the wind and wave parameters over Indian Ocean region obtained from first Ka –band altimeter AltiKa onboard SARAL, a collaborative mission of Indian Space Research Organization (ISRO) and Centre National d'Etudes Spatiales (CNES), France. It also demonstrates a real time application of SARAL data by assimilating the wave height in a wave model operational at the Space Applications Centre, ISRO. State-of–the art coastal wave model Simulating Wave Near shore (SWAN) is used for this purpose. The well-tested optimal interpolation technique is adopted for assimilation. Before proceeding to the assimilation per se, SARAL/AltiKa Wind and Significant Wave Height (SWH) have been validated using in- situ observations and WAVEWATCH III model. Apart from assessment of wind and wave data quality, this also served the purpose of providing error covariance to be used in assimilation. Supremacy of the assimilation run over parallel control run without assimilation has been judged by comp...

Published
2015

22. Geophysical Model Function for Wind Speed Retrieval from SARAL/AltiKa

Author

M. T. Bushair, Suchandra Aich Bhowmick, and R. M. Gairola

Subjects
Meteorology, Function (mathematics), Geophysics, Oceanography, Wind speed, law.invention, Geography, Radar altimeter, law, Wave height, Surface roughness, Ka band, Altimeter, Significant wave height, Remote sensing
Abstract

With the launch of SARAL/AltiKa altimeter, efforts have been made to develop wind speed retrieval algorithms. Here we present two algorithms for estimating and validating wind speed from AltiKa. The first method is based on a theoretical Geophysical Model Function (GMF) using forward model simulations for Ka band specifications. The second is the model function developed using the matched database of input and output vectors of Normalized Radar Cross Section (NRCS) from AltiKa and wind speed measurements from concurrent Jason-2 altimeters. Since the NRCS depends on both the surface roughness due to surface wind speed and on mean square slope of the surfaces, the significant wave height is used along with wind speed for model development as an proxy variable. Both the theoretical and empirical GMFs are evaluated for retrieval of wind speed from AltiKa and validated with NDBC buoys data. The empirical model provide wind speed retrieval accuracy of 1.4 m/s. The accuracy of wind retrievals from theoretical mo...

Published
2015

23. Cross Calibration of the OceanSAT -2 Scatterometer With QuikSCAT Scatterometer Using Natural Terrestrial Targets

Author

Suchandra Aich Bhowmick, Raj Kumar, and A. S. Kiran Kumar

Subjects
Cross Calibration, Meteorology, Planetary boundary layer, Calibration, Range (statistics), General Earth and Planetary Sciences, Environmental science, Satellite, Electrical and Electronic Engineering, Scatterometer, Absolute calibration, Standard deviation, Remote sensing
Abstract

The accuracy of ocean surface wind vectors measured by satellite-borne scatterometers depends on measured backscattering coefficient (σ°). Hence, an in-flight calibration of a satellite scatterometer is essential as this is not guaranteed by its prelaunch absolute calibration. The postlaunch calibration of σ° is also required to monitor the time evolution of the accuracy of measured σ °. This is performed using relative calibration over land targets with minor spatiotemporal variation of σ°. A few such targets are the Amazon rainforest, Greenland, Antarctica, etc. In this paper, relative calibration of σ° from the OceanSAT-2 Scatterometer (OSCAT) has been carried out by comparing it with a similar quantity from the Quick Scatterometer (QuikSCAT) for November 2009. The differences between the average σ° of QuikSCAT and that of OSCAT have been calculated globally to check the overall consistency. Over the calibration sites, the differences are within ±0.25 dB. Histograms of differences in ascending/descending passes and fore/aft looks of OSCAT have also been analyzed over the calibration sites. These indicate that look bias in OSCAT σ° is within the range of ±0.5 dB. It is also evident that pass biases, i.e., differences between ascending and descending passes, exist over the Amazon rainforest for both QuikSCAT and OSCAT. This diurnal variation in σ° may go up to 1.25 dB in OSCAT. Further, computations of daily average and standard deviation over the calibration site show that mean OSCAT σ° is consistent with mean QuikSCAT σ°, whereas the standard deviation in OSCAT is marginally higher. Further, time-series analysis of OSCAT σ° shows its temporal stability.

Published
2014

25. An Assessment of the Performance of ISRO’s SCATSAT-1 Scatterometer

Author

James Cotton, Bryan Stiles, Anuja Sharma, Anton Verhoef, Suchandra Aich Bhowmick, Ernesto Rodriguez, Ad Stoffelen, Alexander Fore, Christophe Payan, and Raj Kumar

Subjects
Multidisciplinary, Environmental science, Scatterometer, Remote sensing
Published
2019

26. Swell Propagation over Indian Ocean Region

Author

Raj Kumar, Abhijit Sarkar, Suchandra Aich Bhowmick, and Sutapa Chaudhuri

Subjects
Meteorology, Infragravity wave, lcsh:Ocean engineering, Swell, lcsh:Oceanography, Ocean surface topography, Sea breeze, Climatology, Wind wave, lcsh:TC1501-1800, lcsh:GC1-1581, Ocean heat content, Tropical cyclone, Significant wave height, Geology
Abstract

Swells are the ocean surface gravity waves that have propagated out of their generating fetch to the distant coasts without significant attenuation. Therefore they contain a clear signature of the nature and intensity of wind at the generation location. This makes them a precursor to various atmospheric phenomena like distant storms, tropical cyclones, or even large scale sea breeze like monsoon. Since they are not affected by wind once they propagate out of their generating region, they cannot be described by regional wave models forced by local winds. However, their prediction is important, in particular, for ship routing and off shore structure designing. In the present work, the propagation of swell waves from the Southern Ocean and southern Indian Ocean to the central and northern Indian Ocean has been studied. For this purpose a spectral ocean Wave Model (WAM) has been used to simulate significant wave height for 13 years from 1993–2005 using NCEP blended winds at a horizontal spatial resolution of 1° × 1°. It has been observed that Indian Ocean, with average wave height of approximately 2–3 m during July, is mostly dominated by swell waves generated predominantly under the extreme windy conditions prevailing over the Southern Ocean and southern Indian Ocean. In fact the swell waves reaching the Indian Ocean in early or mid May carry unique signatures of monsoon arriving over the Indian Subcontinent. Pre-monsoon month of April contains low swell waves ranging from 0.5–1 m. The amplitudes subsequently increase to approximately 1.5–2 meters around 7–15 days prior to the arrival of monsoon over the Indian Subcontinent. This embedded signature may be utilized as one of the important oceanographic precursor to the monsoon onset over the Indian Ocean.

Published
2011

27. Relative Calibration Using Natural Terrestrial Targets: A Preparation Towards Oceansat-2 Scatterometer

Author

Rahul Nigam, A. Sarkar, Suchandra Aich Bhowmick, K. N. Babu, and Raj Kumar

Subjects
Meteorology, Calibration (statistics), Scatterometer, Snow, Stability (probability), Standard deviation, law.invention, Azimuth, law, General Earth and Planetary Sciences, Environmental science, Electrical and Electronic Engineering, Radar, Space research, Remote sensing
Abstract

Scatterometer instruments transmit a series of microwave pulses and measure the returned echo to determine the normalized radar cross section (σ0) over the target to derive the near-ocean-surface wind vector. Accuracy of the derived wind vector over the data sparse oceans therefore depends on the accuracy of σ0 measurement. For this purpose, accurate calibration of the scatterometer is required. As a preparation toward calibration of the Oceansat-2 mission, of the Indian Space Research Organisation, a relative calibration technique has been proposed in this study by selecting homogeneous areas over the globe with isotropic radar response and temporally stable signature of σ0. For this purpose, the daily averaged σ0 and Level-2A (L2A) σ0 measurements of the QuikSCAT scatterometer have been used. Analyzing the monthly mean and standard deviation in σ0 for the period of 2005-2006, several regions are chosen which have a quasi-isotropic radar response and minimal temporal variation in σ0. The analysis shows that the selected areas over Antarctica and Greenland with permanent ice covers have temporally stable signatures of σ0. The regions like the Amazon forests and parts of Australia also show high temporal stability of σ0 but greater standard deviation than the snow-covered areas. The QuikSCAT L2A data have also been used to study the day-night variation and azimuthal dependence of the σ0 over these targets. The present work demonstrated that quasi-uniform natural sites such as Sahara, Amazon forest, Kutch, Greenland region, and Antarctica region, covering wide dynamic range of σ0, can be used for the purpose of calibration.

Published
2011

28. Sensitivity Study of a Coastal Wave Model for Prediction of Ocean Waves over Indian Ocean Region

Author

Sutapa Chaudhuri, Raj Kumar, Abhijit Sarkar, and Suchandra Aich Bhowmick

Subjects
Physics, Meteorology, Forcing (mathematics), Oceanography, Wind wave model, Wave model, Indian ocean, Climatology, Physics::Space Physics, Wind wave, Altimeter, Sensitivity (control systems), Significant wave height, Physics::Atmospheric and Oceanic Physics
Abstract

In this article, sensitivity of the SWAN coastal wave model towards wind inputs and physics options has been performed over the Indian Ocean by forcing the model with analyzed GDAS winds. Wind forcing simulations show that the model is sensitive to the wind errors. The simulations obtained using different physics options have been compared with altimeter and in situ data. The study indicates that the model with Janssen physics options simulates the significant wave height with a fairly high degree of accuracy. It has also been observed that the simulations are not too sensitive to the choice of propagation schemes.

Published
2011

29. Inter-Comparison of Numerical Model Generated Surface Winds with QuikSCAT Winds over the Indian Ocean

Author

Raj Kumar, S. K. Deb, Suchandra Aich Bhowmick, and Abhijit Sarkar

Subjects
Indian ocean, Geography, Meteorology, Medium range, Climatology, Surface winds, Ocean current, Satellite, Oceanography, Wind speed
Abstract

The accurate surface wind in the equatorial Indian Ocean is crucial for modeling ocean circulation over this region. In this study, the surface wind analysis generated at the European Center for Medium Range Weather Forecasts (ECMWF) and the National Centers for Environmental Prediction (NCEP) are compared with NASA QuikSCAT satellite derived Level2B (swath level) and Level3 (gridded) surface winds for the year 2005. It is observed that the ECMWF winds exhibit speed bias of 1.5 m/s with respect to QuikSCAT Level3 in the southern equatorial Indian Ocean. The NCEP winds are found to exhibit speed bias (1.0–1.5 m/s) in the southern equatorial Indian Ocean specifically during January–February 2005. The biases are also observed in the analysis when compared with Level2B product as well; however, it is less in comparison to Level3 products. The amplitude of daily variations of both ECMWF and NCEP wind speed in Bay of Bengal and parts of the Arabian Sea is about 80% of that in QuikSCAT, while in the equatorial I...

Published
2009

30. Improvement in predictability of waves over the Indian Ocean

Author

Suhe Surendran, Vihang Bhatt, Sujit Basu, Sulagna Ray, Abhijit Sarkar, Vijay K. Agarwal, Raj Kumar, and Suchandra Aich Bhowmick

Subjects
Atmospheric Science, Meteorology, Scatterometer, Swell, Physics::Geophysics, Wind wave model, Wave model, Surface wave, Climatology, Wind wave, Earth and Planetary Sciences (miscellaneous), Altimeter, Significant wave height, Physics::Atmospheric and Oceanic Physics, Geology, Water Science and Technology
Abstract

Accurate prediction of ocean surface waves is a challenging task with many associated difficulties. Availability of good quality wind and wave information from satellite platforms inspired the scientific community to assimilate such data in various spectral wave models for enhancing the accuracy of prediction. Over the Indian Ocean, which is the region of interest for the present study, wave heights in extreme situation can go up to 12–14 m, thereby increasing the probability of coastal hazards. This region is further governed by the southern ocean swells that propagate thousands of kilometers. These are, in general, not well captured by the spectral wave models. Therefore, assimilation of altimeter data in open ocean wave model WAM has been attempted with the aim of enhancing the quality of prediction of significant wave height. Further, simulated wave spectra have been assimilated in a coastal wave model SWAN. This assimilation has been found to significantly improve the prediction of the height of wind waves as well as swell waves.

Published
2008

31. Validation of SWH and SSHA from SARAL/AltiKa Using Jason-2 and In-Situ Observations

Author

R. M. Gairola, Rashmi Sharma, K. N. Babu, Archit Shukla, Suchandra Aich Bhowmick, Pascal Bonnefond, Ramasamy Venkatesan, Nicolas Picot, Raj Kumar, Government of Nepal Ministry of Science, Technology & Environment, Space Applications Centre (ISRO), Microsoft Research, SAC/ISRO, Géoazur (GEOAZUR 7329), Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud])-Centre National de la Recherche Scientifique (CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA), Observatoire de la Côte d'Azur (OCA), Centre National de la Recherche Scientifique (CNRS), Centre National d'Études Spatiales [Toulouse] (CNES), Space Applications Centre [Ahmedabad] (SAC), Indian Space Research Organisation (ISRO), Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud])-Centre National de la Recherche Scientifique (CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA), and Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
010504 meteorology & atmospheric sciences, Buoy, Meteorology, Anomaly (natural sciences), 0211 other engineering and technologies, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, 02 engineering and technology, Sea-surface height, Oceanography, 01 natural sciences, Geography, 13. Climate action, Satellite, 14. Life underwater, Altimeter, Space research, Significant wave height, 021101 geological & geomatics engineering, 0105 earth and related environmental sciences, Remote sensing
Abstract

International audience; The focus of this study is the validation of significant wave height (SWH) and sea surface height anomaly (SSHA) obtained from the first Ka-band altimeter AltiKa onboard SARAL (Satellite for ARGOS and Altimeters). It is a collaborative mission of the Indian Space Research Organization and Centre National d'Etudes Spatiales (CNES). This is done using in-situ observations from buoy and Jason-2 measurements. Validation using buoy observations are at particular locations while that using Jason-2 altimeter is an attempt towards global validation of Altika products. The results clearly indicate that the SARAL/AltiKa provide high-quality data and the errors are within a predefined range of accuracy. A parallel validation of SWH from other altimeters, which monitored ocean since last decade, like EnviSAT and Jason-2 was also performed with buoy observations. The results clearly show that the accuracy of AltiKa SWH is much better than EnviSAT and comparable to reference mission Jason-2. The accuracy is quite good for the calm sea while in the rough seas the accuracy degrades some. The inter-comparison of SARAL/AltiKa SSHA with Jason-2 indicates a fair match between them. These validation exercises demonstrate the high quality of AltiKa products, usable for practical applications.

Published
2015

32. CAPE - A link amid thermodynamics and microphysics for the occurrence of severe thunderstorms

Author

Sutapa Chaudhuri and Suchandra Aich Bhowmick

Subjects
Physics, Atmospheric Science, Cloud microphysics, Pre monsoon, Geophysics, Thermodynamics
Abstract

Lkkj & bl 'kks/k&i= dk mÌs’; dksydkrk ¼22°32¢] 88°20¢½ esa ekulwu iwoZ _rq ¼vizSy&ebZ½ ds nkSjku xtZ ds lkFk vkus okys Hkh"k.k rwQkuksa dh mRifÙk vkSj fodkl esa lgk;d es?k dh lw{e HkkSfrdh; izfØ;kvksa dh tk¡p djuk gSA bl v/;;u ls ;g irk pyk gS fd dksydkrk esa ekulwu&iwoZ _rq ds nkSjku xtZ ds lkFk vkus okys Hkh"k.k rwQkuksa ds nkSjku rkixfrdh;] xfrdh;] es?k dh lw{e HkkSfrdh vkSj fctyh pdeus dks J`a[kykc) djus esa laoguh; miyC/k foHko ÅtkZ ¼lh- ,- ih- bZ-½ lgk;d gSA bl v/;;u ls izkIr gq, ifj.kkeksa ls ;g irk pyk gS fd dksydkrk esa laoguh; miyC/k foHko ÅtkZ 1000 twYl izfr fd- xzk- ds Hkhrj izcy ikbZ xbZ tks eqDr laogu Lrj ¼,y- ,Q- lh-½ ls Åij fu/kkZfjr nkc Lrjksa ds Hkhrj ikbZ xbZ vkSj ok;q dh viMªk¶V xfr ds ln`’k eku fu"izHkkoh mRIykodrk Lrj ¼,y- ,u- ch-½ esa yxHkx 30 - 50 eh-@ lsdsaM ik, x,A bl v/;;u ls ;g Hkh irk pyk gS fd 5 fe- eh- rd ds O;kl ds vkdkj dh c¡wns fLFkj jg ldrh gS ftlds ckn vkdkj c

Published
2006

33. Altimetry for the future: Building on 25 years of progress

Author

Francesco d'Ovidio, Pierre Féménias, Sean Bruinsma, Felix Perosanz, Jerome Bouffard, S. Desai, Alexandre Couhert, Tatyana V. Belonenko, Sinead L. Farrell, Masafumi Kamachi, Rémi Laxenaire, Alexei V. Kouraev, M-Isabelle Pujol, Sandrine Mulet, Ciprian Spatar, Pablo Nilo Garcia, Loren Carrere, Vinca Rosmorduc, Michel Calzas, Marcello Passaro, Francesca Cirillo, Mathieu Hamon, Enrico Ser-Giacomi, Jida Wang, Raj Kumar, Stelios P. Mertikas, Luisella Giulicchi, Eric Jeansou, Benoit Legresy, Corinne Salaün, Donald Richardson, Martin Horwath, Sujit Basu, Rosemary Morrow, Jean-Damien Desjonquères, François Barlier, Cédric Brachet, Cécile Manfredi, Yves Morel, P. K. Gupta, Nicolas Taburet, Ferran Gibert, Anny Cazenave, Sung Yong Kim, Christopher Pearson, Lin Gilbert, Brian D. Dushaw, Johnny A. Johannessen, René Forsberg, Joël Dorandeu, Luciana Fenoglio, Denis Blumstein, C. K. Shum, Debadatta Swain, Stephan Paul, Valerii Vuglinskii, Marco Meloni, Hilary Wilson, Laurent Testut, Sebatian B. Simonsen, John Moyard, Fabien Léger, Andy Shaw, Abdolnabi Abdeh Kolahchi, Andrea Scozzari, Jan Even Øie Nilsen, Anna I. Bulczak, Valerio Poggiali, Rashmi Shah, John Wilkin, Steven Baker, Patrice Klein, Touati Benkouider, Claire Macintosh, Sarah T. Gille, Alexandre Guerin, Gilles Tavernier, Josh K. Willis, Jérôme Benveniste, Cedric Tourain, Emil V. Stanev, Praveen K. Thakur, Lionel Fichen, Céline Tison, Hans Ngodock, Shenfu Dong, Yuanyuan Jia, Sergey A. Lebedev, Nadia Ayoub, Constantin Mavrocordatos, Cédric H. David, Salvatore Dinardo, Yongjun Jia, Berguzar Oztunali Ozbahceci, Sara Fleury, Matthias Raynal, Yannice Faugère, Kathryn A. Kelly, Christian Schwatke, Craig Donlon, Etienne Poirier, Margaret Srinivasan, Remko Scharroo, Helena Antich, Barbara J. Ryan, Sergey V. Prants, Malcolm McMillan, Frédérique Rémy, David T. Sandwell, Annick Sylvestre-baron, Pascal Bonnefond, Fabien Blarel, Mounir Benkiran, Remi Tailleux, Marco Restano, Thierry Guinle, Stefano Vignudelli, Eric Leuliette, Madeleine Cahill, Ali Rami, Saulo Soares, Sophie Le Gac, Bàrbara Barceló-Llull, Claudia C. Carabajal, Veit Helm, Eva Alou-Font, Alejandro Blazquez, David Griffin, Habib B. Dieng, Prakash Chauhan, Albert Garcia-Mondejar, Christian Massari, Christopher J. Banks, Joana Fernandes, Blake A Walter, Nathalie Steunou, Karina Nielsen, Elena Zakharova, Bob Su, Stefania Camici, Frédérique Seyler, Fukai Peng, Denis L. Volkov, Wim Simons, Pieter Visser, Sophie Coutin-Faye, Lionel Gourdeau, Jesús Gómez-Enri, Andreas Schiller, Brian K. Arbic, Svetlana Karimova, Christine Gommenginger, Fanny Piras, Angélique Melet, Steve Coss, Meric Srokosz, Robert G. King, Frédéric Frappart, Fernando S. Paolo, Anna Klos, José Darrozes, Shannon Brown, Loreley Selene Lago, Susheel Adusumilli, Jay F. Shriver, Yves Quilfen, Martina Idžanović, Bernd Uebbing, Daniel Medeiros Moreira, Byron D. Tapley, R. Keith Raney, Frank G. Lemoine, Angelica Tarpanelli, Lara Díaz-Barroso, Jean-François Crétaux, Jean Tournadre, Tamlin M. Pavelsky, Sébastien Trilles, Carolina Nogueira Loddo, Léa Lasson, Stine Kildegaard Rose, Luc Lenain, Philip L. Woodworth, Marie-laure Frery, Saleh Abdalla, Bo Qiu, Stefan Hendricks, Mikhail A. Sokolovskiy, Antonio Sánchez-Román, Martin G. Scharffenberg, Per Knudsen, Andrew Shepherd, Michiel Otten, Sammie Buzzard, Philippe Schaeffer, Nicolas Picot, Luca Brocca, Michel Tsamados, Danielle De Staerke, Frederic Vivier, Nicole Bellefond, Jean-François Minster, Telmo Vieira, Brian D. Beckley, Stylianos Flampouris, Nadya Vinogradova Shiffer, Sergei Rudenko, Camille Noûs, Sabine Arnault, Frédéric Cyr, Liguang Jiang, Nicolas Bercher, Teresa K. Chereskin, Katsumi Takayama, Julienne Stroeve, Andrea Doglioli, Joanna Staneva, Stéphane Calmant, T. Moreau, Julien Le Sommer, David R. Donahue, Nadim Dayoub, Clement Ubelmann, Annie Richardson, Estelle Obligis, Laurent Brodeau, Catherine Prigent, Gérald Dibarboure, Simón Ruiz, LuAnne Thompson, Muriel Berge-Nguyen, Martina Ricko, Hugues Capdeville, Sammy Metref, Roshin P. Raj, Suchandra Aich Bhowmick, Andrey G. Kostianoy, Guillermina Paniagua, Mathilde Cancet, Eero Rinne, Sonia Ponce de León, Cédric Falco, Jianqiang Liu, Lucile Gaultier, Julia Gaudelli, Thierry Medina, Vadim Zinchenko, William Llovel, Eric P. Chassignet, Raymond Zaharia, Svetlana Y. Erofeeva, Lifeng Bao, Ole Baltazar Andersen, Emmanuel Cosme, Anna E. Hogg, Yohanes Budi Sulistioadi, Artur Gil, O. Laurain, Walter H. F. Smith, Ngan Tran, Pierre-Yves Le Traon, Laura Gomez-Navarro, Adrien Paris, Thomas W. K. Armitage, Alejandro Egido, Christopher Watson, João H. Bettencourt, Giuseppe Aulicino, Philippe Escudier, Fangfang Yao, Marco Fornari, Guoqi Han, Florent Lyard, Elisabeth Remy, Lotfi Aouf, Michele Scagliola, Martin Saraceno, Paolo Filippucci, Chao Wang, Zhongxiang Zhao, Juliette Lambin, Evan Mason, Ines Otosaka, Daniele Ciani, Raúl A. Guerrero, Ralf Bennartz, Michael Ablain, Fabrice Hernandez, Xiaoli Deng, John Lillibridge, Oscar Vergara, Marina Levy, Christine Drezen, Pierre Thibaut, Ronan Fablet, Bill Townsend, David Cotton, Sabrina Speich, Clara Lázaro, R. S. Nerem, Danièle Hauser, Pierre Exertier, Yuri Cotroneo, Henryk Dobslaw, Alessandro Di Bella, Karina von Schuckmann, Saskia Esselborn, Benjamin D. Gutknecht, Cecile Marie Margaretha Kittel, Rolf Koenig, Peter Bauer-Gottwein, Franck Borde, Alexander Braun, Christine Provost, Thomas Slater, Laiba Amarouche, Nikolai Maximenko, Raphael Schneider, Victor Zlotnicki, Jacques Verron, Sergei I. Badulin, Andreas Groh, Denise Dettmering, Mark R. Drinkwater, S. Cherchali, Marc Naeije, Fernando Niño, Alessio Domeneghetti, Kuo Hsin Tseng, François Boy, Rashmi Sharma, Laurent Soudarin, Peter A. E. M. Janssen, Robert Ricker, Frédéric Marin, Ananda Pascual, Eduard Makhoul Varona, Yongsheng Zhang, Pierrik Vuilleumier, Louise Sandberg Sørensen, Guillaume Dodet, Pascale Ferrage, Ramiro Ferrari, Yves Du Penhoat, Rodrigo Cauduro Dias de Paiva, S. Labroue, Camila Indira Artana, Joaquín Tintoré, David Brockley, Thierry Penduff, Paolo Cipollini, Augusto Getirana, Cecile Cheymol, Edward D. Zaron, Silvia Barbetta, Pierre Brasseur, Benoit Meyssignac, Matthias Becker, Kehan Yang, Juan Gabriel Fernández, Jean Paul Boy, European Centre for Medium-Range Weather Forecasts (ECMWF), Soil Conservation and Watershed Management Research Institute (SCWRMI), Agricultural Research, Education and Extension Organisation (AREEO ), Scripps Institution of Oceanography (SIO), University of California [San Diego] (UC San Diego), University of California-University of California, Space Applications Centre [Ahmedabad] (SAC), Indian Space Research Organisation (ISRO), Collecte Localisation Satellites (CLS), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Centre National d'Études Spatiales [Toulouse] (CNES), National Space Institute [Lyngby] (DTU Space), Technical University of Denmark [Lyngby] (DTU), Institut Mediterrani d'Estudis Avancats (IMEDEA), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC)-Universidad de las Islas Baleares (UIB), Météo France, Department of Earth and Environmental Sciences [Ann Arbor], University of Michigan [Ann Arbor], University of Michigan System-University of Michigan System, Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Variabilité de l'Océan et de la Glace de mer (VOG), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Institut de Recherche pour le Développement (IRD)-Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Institut de Recherche pour le Développement (IRD)-Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU), Mercator Océan, Société Civile CNRS Ifremer IRD Météo-France SHOM, Universita degli studi di Napoli 'Parthenope' [Napoli], Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), P.P. Shirshov Institute of Oceanology (SIO), Russian Academy of Sciences [Moscow] (RAS), Department of Space and Climate Physics [UCL London], Mullard Space Science Laboratory (MSSL), University College of London [London] (UCL)-University College of London [London] (UCL), National Oceanography Centre (NOC), Institute of Geodesy and Geophysics [Wuhan], Chinese Academy of Sciences [Wuhan Branch], Istituto di Ricerca per la Protezione Idrogeologica [Perugia] (IRPI), Consiglio Nazionale delle Ricerche [Roma] (CNR), Géoazur (GEOAZUR 7329), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud]), DTU Environment, Department of Environmental Engineering, Technische Universität Darmstadt (TU Darmstadt), Centre National d'Études Spatiales [Toulouse] (CNES), St Petersburg State University (SPbU), Agence Spatiale Algérienne = Algerian Space Agency (ASAL), Vanderbilt University [Nashville], European Space Research Institute (ESRIN), European Space Agency (ESA), Centre for Marine Technology and Ocean Engineering (CENTEC), Instituto Superior Técnico, Universidade Técnica de Lisboa (IST), Systèmes de Référence Temps Espace (SYRTE), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), European Space Research and Technology Centre (ESTEC), Ecole et Observatoire des Sciences de la Terre (EOST), Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), INSU Division Technique de l'INSU [Site de Brest], Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Queen's University [Kingston, Canada], OceanNext, Géosciences Environnement Toulouse (GET), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Institute of Oceanology, Polish Academy of Sciences (IO-PAN), Polska Akademia Nauk = Polish Academy of Sciences (PAN), Centre for Polar Observation and Modelling (CPOM), Natural Environment Research Council (NERC), Australian Institute of Marine Science [Townsville] (AIMS Townsville), Australian Institute of Marine Science (AIMS), NOVELTIS [Sté], Science Systems and Applications, Inc. [Hampton] (SSAI), International Space Science Institute [Bern] (ISSI), Center for Ocean-Atmospheric Prediction Studies (COAPS), Florida State University [Tallahassee] (FSU), Indian Institute of Remote Sensing (IIRS), Istituto di Science Marine (ISMAR ), Consiglio Nazionale delle Ricerche (CNR), European Centre for Space Applications and Telecommunications (ECSAT), Airbus Group [Germany], Airbus [France], School of Earth Sciences [Columbus], Ohio State University [Columbus] (OSU), Satellite Oceanographic Consultants Ltd (SATOC), Northwest Atlantic Fisheries Centre (NWAFC), Fisheries and Oceans Canada (DFO), Processus et interactions de fine échelle océanique (PROTEO), School of Engineering [Callaghan], University of Newcastle [Australia] (UoN), Deutsches Geodätisches Forschungsinstitut (DGFI-TUM), Technische Universität Munchen - Université Technique de Munich [Munich, Allemagne] (TUM), SOCIB Balearic Islands Coastal Ocean Observing and Forecasting System, German Research Centre for Geosciences - Helmholtz-Centre Potsdam (GFZ), Laboratoire d'Océanographie Physique et Spatiale (LOPS), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Institut méditerranéen d'océanologie (MIO), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Toulon (UTLN)-Centre National de la Recherche Scientifique (CNRS), Department of Civil Chemical Environmental and Materials Engineering [Bologna] (DICAM), University of Bologna, NOAA Office of Satellite and Product Operations (OSPO), NOAA National Environmental Satellite, Data, and Information Service (NESDIS), National Oceanic and Atmospheric Administration (NOAA)-National Oceanic and Atmospheric Administration (NOAA), NOAA Atlantic Oceanographic and Meteorological Laboratory (AOML), National Oceanic and Atmospheric Administration (NOAA), Oregon State University (OSU), IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT), Département Mathematical and Electrical Engineering (IMT Atlantique - MEE), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT), Equipe Observations Signal & Environnement (Lab-STICC_OSE), Laboratoire des sciences et techniques de l'information, de la communication et de la connaissance (Lab-STICC), École Nationale d'Ingénieurs de Brest (ENIB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS)-Université Bretagne Loire (UBL)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-École Nationale d'Ingénieurs de Brest (ENIB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS)-Université Bretagne Loire (UBL)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Université de Perpignan Via Domitia (UPVD), Department of Geographical Sciences [College Park], University of Maryland [College Park], University of Maryland System-University of Maryland System, Institut für Geodäsie und Geoinformationstechnik, Technische Universität Berlin (TU), Interdisciplinary Centre of Marine and Environmental Research [Matosinhos, Portugal] (CIIMAR), Universidade do Porto, Centro de Investigaciones del Mar y la Atmósfera (CIMA), Facultad de Ciencias Exactas y Naturales [Buenos Aires] (FCEyN), Universidad de Buenos Aires [Buenos Aires] (UBA)-Universidad de Buenos Aires [Buenos Aires] (UBA)-Consejo Nacional de Investigaciones Científicas y Técnicas [Buenos Aires] (CONICET), Institut für Planetare Geodäsie, Lohrmann-Observatorium, Technische Universität Dresden = Dresden University of Technology (TU Dresden), Universidad Nacional de Mar del Plata [Mar del Plata] (UNMdP), SPACE - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Environmental Fluid Mechanics Laboratory [Daejeon] (EFML), Korea Advanced Institute of Science and Technology (KAIST), Ecole Normale Supérieure Paris-Saclay (ENS Paris Saclay), Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA (UMR_8112)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-CY Cergy Paris Université (CY), Austral, Boréal et Carbone (ABC), Kansas State University, University of North Carolina [Chapel Hill] (UNC), University of North Carolina System (UNC), University of Tasmania [Hobart, Australia] (UTAS), Rutgers, The State University of New Jersey [New Brunswick] (RU), Rutgers University System (Rutgers), Institute of Arctic and Alpine Research (INSTAAR), University of Colorado [Boulder], Water Problems Institute (WPI), the Russian Academy of Sciences [Moscow, Russia] (RAS), Portland State University [Portland] (PSU), Applied Physics Laboratory [Seattle] (APL-UW), University of Washington [Seattle], Scripps Institution of Oceanography (SIO - UC San Diego), University of California (UC)-University of California (UC), Danmarks Tekniske Universitet = Technical University of Denmark (DTU), Météo-France Direction Interrégionale Sud-Est (DIRSE), Météo-France, Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Università degli Studi di Napoli 'Parthenope' = University of Naples (PARTHENOPE), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), National Research Council of Italy | Consiglio Nazionale delle Ricerche (CNR), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud]), Technische Universität Darmstadt - Technical University of Darmstadt (TU Darmstadt), Agence Spatiale Européenne = European Space Agency (ESA), University of Newcastle [Callaghan, Australia] (UoN), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), University of Bologna/Università di Bologna, IMT Atlantique (IMT Atlantique), École Nationale d'Ingénieurs de Brest (ENIB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS)-Université Bretagne Loire (UBL)-IMT Atlantique (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-École Nationale d'Ingénieurs de Brest (ENIB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS)-Université Bretagne Loire (UBL)-IMT Atlantique (IMT Atlantique), Technical University of Berlin / Technische Universität Berlin (TU), Universidade do Porto = University of Porto, Consejo Nacional de Investigaciones Científicas y Técnicas [Buenos Aires] (CONICET)-Facultad de Ciencias Exactas y Naturales [Buenos Aires] (FCEyN), Universidad de Buenos Aires [Buenos Aires] (UBA)-Universidad de Buenos Aires [Buenos Aires] (UBA), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique et Atmosphères = Laboratory for Studies of Radiation and Matter in Astrophysics and Atmospheres (LERMA), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-CY Cergy Paris Université (CY), Group on Earth Observations (GEO), Institute of Arctic Alpine Research [University of Colorado Boulder] (INSTAAR), Department of Water Resources, UT-I-ITC-WCC, Faculty of Geo-Information Science and Earth Observation, Abdalla S., Abdeh Kolahchi A., Ablain M., Adusumilli S., Aich Bhowmick S., Alou-Font E., Amarouche L., Andersen O.B., Antich H., Aouf L., Arbic B., Armitage T., Arnault S., Artana C., Aulicino G., Ayoub N., Badulin S., Baker S., Banks C., Bao L., Barbetta S., Barcelo-Llull B., Barlier F., Basu S., Bauer-Gottwein P., Becker M., Beckley B., Bellefond N., Belonenko T., Benkiran M., Benkouider T., Bennartz R., Benveniste J., Bercher N., Berge-Nguyen M., Bettencourt J., Blarel F., Blazquez A., Blumstein D., Bonnefond P., Borde F., Bouffard J., Boy F., Boy J.-P., Brachet C., Brasseur P., Braun A., Brocca L., Brockley D., Brodeau L., Brown S., Bruinsma S., Bulczak A., Buzzard S., Cahill M., Calmant S., Calzas M., Camici S., Cancet M., Capdeville H., Carabajal C.C., Carrere L., Cazenave A., Chassignet E.P., Chauhan P., Cherchali S., Chereskin T., Cheymol C., Ciani D., Cipollini P., Cirillo F., Cosme E., Coss S., Cotroneo Y., Cotton D., Couhert A., Coutin-Faye S., Cretaux J.-F., Cyr F., d'Ovidio F., Darrozes J., David C., Dayoub N., De Staerke D., Deng X., Desai S., Desjonqueres J.-D., Dettmering D., Di Bella A., Diaz-Barroso L., Dibarboure G., Dieng H.B., Dinardo S., Dobslaw H., Dodet G., Doglioli A., Domeneghetti A., Donahue D., Dong S., Donlon C., Dorandeu J., Drezen C., Drinkwater M., Du Penhoat Y., Dushaw B., Egido A., Erofeeva S., Escudier P., Esselborn S., Exertier P., Fablet R., Falco C., Farrell S.L., Faugere Y., Femenias P., Fenoglio L., Fernandes J., Fernandez J.G., Ferrage P., Ferrari R., Fichen L., Filippucci P., Flampouris S., Fleury S., Fornari M., Forsberg R., Frappart F., Frery M.-L., Garcia P., Garcia-Mondejar A., Gaudelli J., Gaultier L., Getirana A., Gibert F., Gil A., Gilbert L., Gille S., Giulicchi L., Gomez-Enri J., Gomez-Navarro L., Gommenginger C., Gourdeau L., Griffin D., Groh A., Guerin A., Guerrero R., Guinle T., Gupta P., Gutknecht B.D., Hamon M., Han G., Hauser D., Helm V., Hendricks S., Hernandez F., Hogg A., Horwath M., Idzanovic M., Janssen P., Jeansou E., Jia Y., Jiang L., Johannessen J.A., Kamachi M., Karimova S., Kelly K., Kim S.Y., King R., Kittel C.M.M., Klein P., Klos A., Knudsen P., Koenig R., Kostianoy A., Kouraev A., Kumar R., Labroue S., Lago L.S., Lambin J., Lasson L., Laurain O., Laxenaire R., Lazaro C., Le Gac S., Le Sommer J., Le Traon P.-Y., Lebedev S., Leger F., Legresy B., Lemoine F., Lenain L., Leuliette E., Levy M., Lillibridge J., Liu J., Llovel W., Lyard F., Macintosh C., Makhoul Varona E., Manfredi C., Marin F., Mason E., Massari C., Mavrocordatos C., Maximenko N., McMillan M., Medina T., Melet A., Meloni M., Mertikas S., Metref S., Meyssignac B., Minster J.-F., Moreau T., Moreira D., Morel Y., Morrow R., Moyard J., Mulet S., Naeije M., Nerem R.S., Ngodock H., Nielsen K., Nilsen J.E.O., Nino F., Nogueira Loddo C., Nous C., Obligis E., Otosaka I., Otten M., Oztunali Ozbahceci B., P. Raj R., Paiva R., Paniagua G., Paolo F., Paris A., Pascual A., Passaro M., Paul S., Pavelsky T., Pearson C., Penduff T., Peng F., Perosanz F., Picot N., Piras F., Poggiali V., Poirier E., Ponce de Leon S., Prants S., Prigent C., Provost C., Pujol M.-I., Qiu B., Quilfen Y., Rami A., Raney R.K., Raynal M., Remy E., Remy F., Restano M., Richardson A., Richardson D., Ricker R., Ricko M., Rinne E., Rose S.K., Rosmorduc V., Rudenko S., Ruiz S., Ryan B.J., Salaun C., Sanchez-Roman A., Sandberg Sorensen L., Sandwell D., Saraceno M., Scagliola M., Schaeffer P., Scharffenberg M.G., Scharroo R., Schiller A., Schneider R., Schwatke C., Scozzari A., Ser-giacomi E., Seyler F., Shah R., Sharma R., Shaw A., Shepherd A., Shriver J., Shum C.K., Simons W., Simonsen S.B., Slater T., Smith W., Soares S., Sokolovskiy M., Soudarin L., Spatar C., Speich S., Srinivasan M., Srokosz M., Stanev E., Staneva J., Steunou N., Stroeve J., Su B., Sulistioadi Y.B., Swain D., Sylvestre-baron A., Taburet N., Tailleux R., Takayama K., Tapley B., Tarpanelli A., Tavernier G., Testut L., Thakur P.K., Thibaut P., Thompson L., Tintore J., Tison C., Tourain C., Tournadre J., Townsend B., Tran N., Trilles S., Tsamados M., Tseng K.-H., Ubelmann C., Uebbing B., Vergara O., Verron J., Vieira T., Vignudelli S., Vinogradova Shiffer N., Visser P., Vivier F., Volkov D., von Schuckmann K., Vuglinskii V., Vuilleumier P., Walter B., Wang J., Wang C., Watson C., Wilkin J., Willis J., Wilson H., Woodworth P., Yang K., Yao F., Zaharia R., Zakharova E., Zaron E.D., Zhang Y., Zhao Z., Zinchenko V., Zlotnicki V., Technical University of Munich (TUM), European Space Agency, National Aeronautics and Space Administration (US), Centre National D'Etudes Spatiales (France), Laboratoire des Écoulements Géophysiques et Industriels [Grenoble] (LEGI), Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Recherche pour le Développement (IRD)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA), Sorbonne Université (SU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Sorbonne Université (SU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Lab-STICC_IMTA_CID_TOMS, Université de Brest (UBO)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Université Bretagne Loire (UBL)-Centre National de la Recherche Scientifique (CNRS)-Université de Bretagne Sud (UBS)-École Nationale d'Ingénieurs de Brest (ENIB)-Université de Brest (UBO)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Université Bretagne Loire (UBL)-Centre National de la Recherche Scientifique (CNRS)-Université de Bretagne Sud (UBS)-École Nationale d'Ingénieurs de Brest (ENIB), Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)

Subjects
Cryospheric science, Atmospheric Science, Earth observation, 010504 meteorology & atmospheric sciences, UT-Hybrid-D, Oceanography, 01 natural sciences, Cryospheric sciences, SDG 13 - Climate Action, Aerospace & Aeronautics, Cryosphere, Satellite altimetry, 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, Geodetic datum, ddc, Ocean surface topography, Geophysics, Section (archaeology), [SDE]Environmental Sciences, Astronomical and Space Sciences, Geology, Altimetria espacial, Coastal oceanography, Meteorology, Hidrologia, Aerospace Engineering, ITC-HYBRID, 0103 physical sciences, Geoid, Oceonografia, Sea level, SDG 14 - Life Below Water, 14. Life underwater, Altimeter, Criosfera, Life Below Water, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, 0105 earth and related environmental sciences, Mechanical Engineering, Hydrology, Astronomy and Astrophysics, Climate Action, Earth system science, [SDU]Sciences of the Universe [physics], 13. Climate action, Space and Planetary Science, ITC-ISI-JOURNAL-ARTICLE, General Earth and Planetary Sciences
Abstract

International Altimetry Team., 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., At the forefront of this support, we must obviously mention the space agencies CNES, ESA and NASA which have played and still play a decisive role in the development and launch of several prominent altimetry missions from the outset. Other agencies such as DLR, EUMETSAT, ISRO, NOAA, NSOAS and organizations such as CMEMS, also contribute significantly to developments in all forms of altimetry.

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