JASON-1 CALVAL experiences in Cape of Begur and Ibiza island

The direct and indirect calibration experiences made at the Cape of Begur area in 1999, 2000 and 2002, for Topex/Poseidon and at the Ibiza island in 2003 have contributed to the international campaigns made at Harvest (USA), Corsica (France) and Bass (Australia). The main objective of IBIZA 2003 campaign has been the determination of the instantaneous sea surface/marine geoid gradient along Jason-1 tracks using a GPS catamaran and a network of GPS located in Portinatx and Ibiza and San Antonio harbours. The marine geoid will be used to relate the tide gauge coastal data with the altimeter data. We present the first results obtained with static and kinematic analysis of the data using different softwares.Peer ReviewedPostprint (published version

Altimetry for the future: Building on 25 years of progress

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

Altimetry for the future: building on 25 years of progress

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

Ground-based GPS imaging of ionospheric post-seismic signal

International audienceDuring the Demeter mission, a continuous global positioning system (GPS) ionospheric tomography above Europe, Japan and California will be performed with the Service and Products of ionosphere Electronic Content and Tropospheric Refractive index over Europe (SPECTRE) experiment. The main goal of the conducted observations is to detect and characterize post-seimic ionospheric perturbations associated to seismic generated waves, more precisely near field seismic waves, far field Rayleigh waves and tsunamis. We first review the theory describing post-seismic ionospheric signals as well as the most recent observations of these signals. We then present the description of the tomographic procedure used for the SPECTRE experiment, as well as the obtained tomographic models. We finally draw the perspective of such observations

Continuous Monitoring of the Jason-l and TOPEX/POSEIDON Ocean Altimetry Missions from Dedicated Calibration Sites

We present calibration results from Jason-1 and TOPEX/POSEIDON overflights of the three dedicated verification sites: 1) a California offshore oil platform (Harvest); 2) the Mediterranean island of Corsica (Cape Senetosa), and 3) the Bass Strait off the coast of Tasmania. The high-accuracy of the Jason-1 measurement system is evident in the results from the dedicated calibration experiments. These experiments do indicate, however, that the Jason-1 sea-surface-height (SSH) measurements are biased high by approximately 12-15 cm. We discuss the implications of geographically correlated errors on the determination of the SSH bias

A satellite ocean color observation operator system for eutrophication assessment in coastal waters

International audienceDuring the INSEA project the potential positive role that remote sensing products can play in coastal eutrophication assessment systems using assimilation into coupled hydrodynamic–biogeochemical models has been shown. However, products derived from satellite ocean color data continue to suffer from high levels of inaccuracy when compared with in situ measurements of the surface layer of the ocean. This has been particularly pronounced for coastal waters and waters optically classified as Case-II. The early success of using empirical relationships between chlorophyll and simple band ratios to derive estimates of surface layer chlorophyll from the first ocean color satellite sensors' data (i.e. CZCS), has led mainstream ocean color remote sensing and standard ocean color products towards following this approach for subsequent sensors (e.g. SeaWiFS and MODIS). Chlorophyll has continued to be the main focus product but is only related to one of the optical properties of sea water, namely the absorption of light by phytoplankton, whereas empirical band ratio approaches use wavelength banded water leaving radiance resultant from all absorption and scattering of light by all the optically active components of the ocean surface layer. We suggest that using approaches that do not fully exploit remote sensing optical data through a parameterization of the optical properties of sea water, is the main reason for the poor performance of many ocean color products when compared with in situ data. This is in concordance with the International Ocean Color Coordinating Group (IOCCG) and following their recent guidelines, novel inherent optical properties approaches (e.g. for MERIS) and the lines of research that are being used in atmospheric remote sensing, we present a demonstration ‘observation operator’ system that is based on biogeochemical model output, optical properties (apparent and inherent), and radiative transfer modeling. In the forward mode we demonstrate the system by producing MODIS and SeaWiFS synthetic images of water leaving radiance for the coastal test sites of INSEA. We show that the observation operator approach has the potential to allow the consistent mapping of model variables into observed quantities which simplifies the transport of measurement errors and reduces the need for approximations inherent in previous approaches. In conclusion we discuss the future development and potential of inversion of the system in order to obtain more accurate ocean color biogeochemical products (including chlorophyll) from satellite radiance data for eutrophication assessment. We also highlight the additional advantages there may be for ecological models from having stronger links to bio-optics