J. Cretaux

J. Cretaux
Paul Sabatier University - Toulouse III | UPS Toulouse · Laboratoire d'Etudes en Géophysique et Océanographie Spatiales - UM 30 (UMR 5566 / UMRD 65) - LEGOS

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185
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Introduction
Skills and Expertise

Publications

Publications (185)
Article
Full-text available
Dams and reservoirs are among the most widespread human-made infrastructures on Earth. Despite their societal and environmental significance, spatial inventories of dams and reservoirs, even for the large ones, are insufficient. A dilemma of the existing georeferenced dam datasets is the polarized focus on either dam quantity and spatial coverage (...
Article
Full-text available
The African continent hosts some of the largest freshwater systems worldwide, characterized by a large distribution and variability of surface waters that play a key role in the water, energy and carbon cycles and are of major importance to the global climate and water resources. Freshwater availability in Africa has now become of major concern und...
Article
The semiarid region of Brazil is highly dependent on reservoirs, and precise bathymetric data are essential for understanding the dynamics and storage variability of these water bodies. This study aimed to develop the application of bathymetric calculation using the observed water level and ICESat-2 satellite terrain profile data of large and mediu...
Article
Full-text available
Access to fresh water is a key issue for the next decades in the context of the Global Warming. The water level of lakes is a fundamental variable which needs to be monitored for this purpose. The radar altimetry constellation brings a worldwide means to this question. Recent advances in radar altimeter on-board tracking modes have allowed in monit...
Article
Full-text available
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 mo...
Article
Full-text available
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 mo...
Article
Full-text available
Radar altimetry is now commonly used to provide long-term monitoring of inland water levels in complement to or for replacing disappearing in situ networks of gauge stations. Recent improvements in tracking and acquisition modes improved the quality the water retrievals. The newly implemented Open Loop mode is likely to increase the number of monit...
Article
Life on Earth vitally depends on the availability of water. Human pressure on freshwater resources is increasing, as is human exposure to weather-related extremes (droughts, storms, floods) caused by climate change. Understanding these changes is pivotal for developing mitigation and adaptation strategies. The Global Climate Observing System (GCOS)...
Article
Full-text available
Despite lakes being a key part of the global water cycle and a crucial water resource, there is limited understanding of whether regional or lake-specific factors control water storage variations in small lakes. Here, we study groups of small, unregulated lakes in North Carolina, Washington, Illinois, and Wisconsin, USA using lake level measurement...
Preprint
Full-text available
Dams and reservoirs are among the most widespread human-made infrastructure on Earth. Despite their societal and environmental significance, spatial inventories of dams and reservoirs, even for the large ones, are insufficient. A dilemma of the existing georeferenced dam datasets is the polarized focus on either dam quantity and spatial coverage (e...
Article
Volume changes and water balances of the lakes on the Tibetan Plateau (TP) are spatially heterogeneous and the lakebasin scale drivers remain unclear. In this study, we comprehensively estimated water volume changes for 1132 lakes larger than 1 km2 and determined the glacier contribution to lake volume change at basin-wide scale using satellite ste...
Article
Full-text available
Lake water height is a key variable in water cycle and climate change studies, which is achievable using satellite altimetry constellation. A method based on data processing of altimetry from several satellites has been developed to interpolate mean lake surface (MLS) over a set of 22 big lakes distributed on the Earth. It has been applied on nadir...
Article
Full-text available
To advance monitoring of surface water resources, new remote sensing technologies including the forthcoming Surface Water and Ocean Topography (SWOT) satellite (expected launch 2022) and its experimental airborne prototype AirSWOT are being developed to repeatedly map water surface elevation (WSE) and slope (WSS) of the world’s rivers, lakes, and r...
Article
Full-text available
The Sentinel-3A and Sentinel-3B satellites were launched, respectively, on 16 February 2016 and 25 April 2018 as part of the European Copernicus program. The Sentinel-3 Surface Topography Mission makes use of the altimeter instruments onboard Sentinel-3A and Sentinel-3B to provide elevation measurements not only of the ocean water level but also of...
Article
Full-text available
The Sentinel-3 Mission Performance Centre (S3MPC) is tasked by the European Space Agency (ESA) to monitor the health of the Copernicus Sentinel-3 satellites and ensure a high data quality to the users. This paper deals exclusively with the effort devoted to the altimeter and microwave radiometer, both components of the Surface Topography Mission (S...
Chapter
The Caspian Sea (CS), located between Europe and Asia, is the largest lake in the world; however, its physical environment and its floor have oceanic characteristics. The CS is composed of a very shallow north sub-basin with a very low salinity mostly below 5 psu. The middle and southern sub-basins are deep and have a salinity of c. 13 psu. To the...
Article
Full-text available
Lake Chad, in the Sahelian zone of west-central Africa, provides food and water to ~50 million people and supports unique ecosystems and biodiversity. In the past decades, it became a symbol of current climate change, held up by its dramatic shrinkage in the 1980s. Despites a partial recovery in response to increased Sahelian precipitation in the 1...
Article
Full-text available
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 ha...
Article
Improved monitoring of inundation area variations in lakes and reservoirs is crucial for assessing surface water resources in a growing population and a changing climate. Although long-record optical satellites, such as Landsat missions, provide sub-monthly observations at fairly fine spatial resolution, cloud contamination often poses a major chal...
Article
The water level variations of the Lake Balkhash, the Kapshagay Reservoir and the Ili River and the linkage with salinity and biological conditions are investigated in this work using different techniques: satellite radar altimetry, in situ gauges, historical archives of fish population counting and field works. We show that it is possible now to mo...
Article
Full-text available
Complete understanding of the hydrological functioning of large-scale intertropical watersheds such as the Lake Chad basin is becoming a high priority in the context of climate change in the near future and increasing demographic pressure. This requires integrated studies of all surface water and groundwater bodies and of their quite-complex interc...
Chapter
The Aral Sea shrank drastically over the past 50 years, largely due to water withdrawal from Amu Darya and Syr Darya rivers for land irrigation. This has led to the separation of Aral Sea into two (in 1986–1987) and then four (in approximately 2010) water bodies. Lakes and enclosed inland seas are integrators of environmental and climate changes oc...
Article
Full-text available
Calibration/Validation (C/V) studies using sites in the oceans have a long history and protocols are well established. Over lakes, C/V allows addressing problems such as the performance of the various retracking algorithms and evaluating the accuracy of the geophysical corrections for continental waters. This is achievable when measurements of spec...
Article
Full-text available
Alpine lakes in the interior of Tibet, the endorheic Changtang Plateau (CP), serve as 'sentinels' of regional climate change. Recent studies indicated that accelerated climate change has driven a widespread area expansion in lakes across the CP, but comprehensive and accurate quantifications of their storage changes are hitherto rare. This study in...
Article
Full-text available
Complete understanding of the hydrological functioning of large scale intertropical watersheds like the Lake Chad basin, which become a high priority in the prospect of near future climate change and increasing demographic pressure, require integrated studies of all surface and groundwater reservoirs and their quite complex interconnections. In thi...
Article
Hydrological and hydrodynamic models are core tools for simulation of large basins and complex river systems associated to wetlands. Recent studies have pointed towards the importance of online coupling strategies, representing feedbacks between floodplain inundation and vertical hydrology. Especially across semi-arid regions, soil-floodplain inter...
Article
Full-text available
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 b...
Article
Full-text available
The India-France SARAL/AltiKa mission is the first Ka-band altimetric mission dedicated to oceanography. The mission objectives are primarily the observation of the oceanic mesoscales but also include coastal oceanography, global and regional sea level monitoring, data assimilation, and operational oceanography. The mission ended its nominal phase...
Poster
Full-text available
The Sentinel-3A Surface Topography Mission has been launched on February 2016 and is now in its second year of operation. Its objectives are to serve primarily the marine operational users but also allow the monitoring of sea ice and land ice, as well as inland water surfaces. A two-channels microwave radiometer (23.8 and 36.5 GHz) similar to the E...
Poster
Full-text available
The Poyang Lake has an important influence on the Yangsé River basin hydrology. However, estimating the discharge input in the river is not straightforward. Indeed, as the cycles of both water bodies are not synchronous, the stage/discharge relationship is ambiguous. At a given period of the hydrological year, the conditions may even inverse and pa...
Conference Paper
Sentinel-3A, launched in February 2016, is part of ESA's long-term commitment to climate monitoring from space. Its suite of instruments for measuring surface topography includes a Microwave Radiometer (MWR) and SRAL, the first delay-Doppler instrument to provide global coverage. SRAL promises fine spatial resolution and reduced noise levels that s...
Poster
Full-text available
Poster briefly summarising the activities to assess the performance of SRAL (the Sentinel-3A altimeter)
Conference Paper
Full-text available
The Aral Sea was the fourth largest lake in the world before 1960. However, it is now four separate water bodies, fed mainly by collector-drainage waters because of excessive upstream irrigation water withdrawals from the two main influent rivers, the Syr Darya and Amu Darya, which is clearly shown on satellite images. The resulting rapid increase...
Article
Full-text available
Caspian Sea level (CSL) has undergone substantial fluctuations during the past several hundred years. The causes over the entire historical period are uncertain, but we investigate here large changes seen in the past several decades. We use climate model-predicted precipitation (P), evaporation (E), and observed river runoff (R) to reconstruct long...
Article
Full-text available
Inland surface waters in tropical environments play a major role in the water and carbon cycle. Remote sensing techniques based on passive, active microwave or optical wavelengths are commonly used to provide quantitative estimates of surface water extent from regional to global scales. However, some of these estimates are unable to detect water un...
Conference Paper
Full-text available
The Upper Niger Basin is located in Western Africa, flowing from Guinea Highlands towards the Sahel region. In this area lies the seasonally inundated Niger Inland Delta, which supports important environmental services such as habitats for wildlife, climate and flood regulation, as well as large fishery and agricultural areas. In this study, we pre...
Article
Full-text available
We examine recent Caspian Sea level change using both satellite radar altimetry and satellite gravity data. The altimetry record for 2002-2015 shows a declining level at a rate that is approximately 20 times greater than the rate of global sea level rise. Seasonal fluctuations are also much larger than in the world oceans. With a clearly defined ge...
Chapter
Altimetry was originally designed for oceanography in the 1970s. It was used to study favorable continental surfaces, especially in hydrology and glaciology, two themes for which monitoring the height of water or ice surfaces is crucial. The principle of the device has not changed but the heterogeneity of the target or the presence of slopes has co...
Chapter
Continental waters have a major impact on life on Earth as well as domestic, industrial and agricultural needs, but they also play an important role in climate variability. Nearly 73% of the worldwide demand for water is met by surface reservoirs (rivers, lakes and artificial reservoirs) and 19% is met by underground reservoirs. The rest is provide...
Poster
Full-text available
In this project we aim at studying the synergistic potential of the use of SWOT futur data over wetlands with L-Band data from radiometers namely SMOS (ESA/CNES) and SMAP (Soil Moisture Active Passive – NASA).
Chapter
Lakes are integrators of environmental change occurring at both the regional and global scale. They present a wide range of behavior on a variety of timescales (cyclic and secular) depending on their morphology and climate conditions. Lakes play a crucial role in retaining and stocking water, and because of the significant global environmental chan...
Article
Full-text available
Lakes are integrators of environmental change occurring at both the regional and global scale. They present a wide range of behavior on a variety of timescales (cyclic and secular) depending on their morphology and climate conditions. Lakes play a crucial role in retaining and stocking water, and because of the significant global environmental chan...
Article
The transfer of energy and water, as well as gaseous components, in the soil–plant–atmosphere system plays a crucial role in many processes involved in climate change. The surface energy balance drives both evapotranspiration (closely linked to the CO2 flux) and sensible heat flux. By providing direct information on heat dissipation efficiency, sur...
Book
Full-text available
In 2009, Thales Alenia Space and Suds-Concepts issued a book called “Climate Change and Satellites”, bringing together an international network of scientists, users, and representatives of major space agencies. With a circulation of over 15,000, mainly in the scientific, governmental and CC community, it was recognized as a leading publication in i...
Conference Paper
Wetlands and land surface waters play a crucial role in the global water and biogeochimal cycles. Since the 80's, remote sensing techniques provide quantitative estimates of open water surfaces over land. They appear to be a valuable tool to monitor natural and anthropogenic evolution of this variable over the globe. A large array of frequencies ha...
Article
Full-text available
This paper describes the Ka-band altimetry payload and system that has been studied for several years by CNES, ALCATEL SPACE and some science laboratories. Altimetry is one of the major elements of the ocean observing system to be made sustainable through the GEOSS (Global Earth Observation System of Systems) and GMES (Global Monitoring of the Envi...
Article
Full-text available
A method of wetland mapping and flood survey based on satellite optical imagery from the Moderate Resolution Imaging Spectroradiometer (MODIS) Terra instrument was used over the Inner Niger Delta (IND) from 2000-2013. It has allowed us to describe the phenomenon of inundations in the delta and to decompose the flooded areas in the IND into open wat...
Article
Full-text available
The SARAL/AltiKa project is based on a single Ka band altimeter (35.75 GHz), which is the first oceanography altimeter to operate at such a high frequency. Ka band offers reduced radar footprint in comparison to traditional Ku band altimeters and negligible ionospheric effects. In this paper we present and evaluate benefits of AltiKa altimeter appl...
Article
Full-text available
The new Global Digital Elevation Model (GDEM v2) has been available since 17 October 2011. With a resolution of approximately 30 m, this model should provide more accurate information than the latest version of Shuttle Radar Topographic Mission (SRTM v4) with a resolution of 90 m outside of the USA. The accuracies of these two recently released dig...
Article
Full-text available
Large reservoirs along rivers regulate downstream flows to generate hydropower but may also store water for irrigation and urban sectors. Reservoir management therefore becomes critical, particularly for transboundary basins, where coordination between riparian countries is needed. Reservoir management is even more important in semiarid regions whe...