A ameaça terrorista e a segurança europeia

Comunicação de Abertura do Seminário “A Ameaça Terrorista e a Segurança Europeia”, realizado em 29 de fevereiro de 2016 no Instituto da Defesa Nacional.info:eu-repo/semantics/publishedVersio

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

Evaluation of the Performances of Radar and Lidar Altimetry Missions for Water Level Retrievals in Mountainous Environment: The Case of the Swiss Lakes

International audienceRadar 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 monitored water bodies owing to the use of an a priori elevation, especially in hilly and mountainous areas. The novelty of this study is to provide a comprehensive evaluation of the performances of the past and current radar altimetry missions according to their acquisition (Low Resolution Mode or Synthetic Aperture Radar) and tracking (close or open loop) modes, and acquisition frequency (Ku or Ka) in a mountainous area where tracking losses of the signal are likely to occur, as well as of the recently launched ICESat-2 and GEDI lidar missions. To do so, we evaluate the quality of water level retrievals from most radar altimetry missions launched after 1995 over eight lakes in Switzerland, using the recently developed ALtimetry Time Series software, to compare the performances of the new tracking and acquisition modes and also the impact of the frequency used. The combination of the Open Loop tracking mode with the Synthetic Aperture Radar acquisition mode on SENTINEL-3A and B missions outperforms the classical Low Resolution Mode of the other missions with a lake observability greater than 95%, an almost constant bias of (-0.17 +/- 0.04) m, a RMSE generally lower than 0.07 m and a R most of the times higher than 0.85 when compared to in situ gauge records. To increase the number of lakes that can be monitored and the temporal sampling of the water level retrievals, data acquired by lidar altimetry missions were also considered. Very accurate results were also obtained with ICESat-2 data with RMSE lower than 0.06 and R higher than 0.95 when compared to in situ water levels. An almost constant bias (0.42 +/- 0.03) m was also observed. More contrasted results were obtained using GEDI. As these data were available on a shorter time period, more analyses are necessary to determine their potential for retrieving water levels

Validation of Jason-3 tracking modes over French rivers

International audienceSatellite nadir radar altimeters have been widely used to measure river and lake surface water elevations. They can now retrieve the elevations of some rivers <200 m wide. However, as these satellite missions are primarily designed to observe ocean surface topography, they are not always able to observe continental surfaces. For steep-sided rivers (i.e. in river valleys no more than a few km wide and surrounded by slopes over 50 m high), altimeters tend to observe the top of the surrounding topography rather than the river itself.The Jason-3 altimetry mission, launched in January 2016, has an alternative instrument operation mode, the so called Open-Loop (OL) or Digital Elevation Model (DEM) tracking mode. This mode is intended to help overcome this issue, by using an on-board DEM. However it was not used in 2016 as the operational mode because of difficulties in defining an accurate on-board global-scale DEM. Mainland France has been chosen to test the OL tracking mode, as water masks and DEMs of sufficient accuracy are available.Following the launch of Jason-3, Jason-2 (its predecessor) was maintained on the same nominal orbit as its follow-on, for more than 6 months. During this tandem period, data from the first 10 Jason-3 cycles (a Jason-2/-3 cycle corresponds to 10 days) were acquired in the traditional Closed-Loop (CL) tracking mode. Jason-3 data from the last 13 cycles were acquired in OL tracking mode. Jason-2 was always in CL tracking mode. Compared to nearby in situ gages and for river wider than 100 m, Jason-3 water elevation anomalies have a RMSE between 0.20 and 0.30 m for most reaches. Jason-3 performance over narrow rivers is similar to that of Jason-2. In CL tracking mode, Jason-3 altimeter tends to be locked over the surrounding topography more frequently than Jason-2 (due to the specific post-launch Jason-2 altimeter tuning). This study shows that Jason-2 observed 60% of river reaches studied (48 of 86 reaches), whereas Jason-3 in OL tracking mode was able to measure all river reaches for every cycle. This result clearly highlights the significant advantages of the OL tracking mode for observation of steep-sided rivers. However, further investigations are required to compute an accurate on-board global-scale DEM and to determine those locations where the use of OL tracking mode is or is not appropriate

AlTiS Software for generating Time-Series of Water Levels from Radar Altimetry Data

International audiencehttps://www.legos.omp.eu/ctoh AlTiS (Altimetry Time Series) is a radar altimetry data processing and visualization software, tailored for fine-grained analysis of small scale water bodies. Its goal is the obtaining water-level time-series derived from the altimetry measurements, but it can also be used to generate time series of any altimetrybased parameters (e.g., corrections applied to the range, backscattering coefficients, or brightness temperatures). AlTiS software is used to compute Water Surface Elevation from nadir altimeters within the ESA-CCI River Discharge precursor project

AlTiS Software for generating Time-Series of Water Levels from Radar Altimetry Data

International audiencehttps://www.legos.omp.eu/ctoh AlTiS (Altimetry Time Series) is a radar altimetry data processing and visualization software, tailored for fine-grained analysis of small scale water bodies. Its goal is the obtaining water-level time-series derived from the altimetry measurements, but it can also be used to generate time series of any altimetrybased parameters (e.g., corrections applied to the range, backscattering coefficients, or brightness temperatures). AlTiS software is used to compute Water Surface Elevation from nadir altimeters within the ESA-CCI River Discharge precursor project

Tracking far-range volcanogenic air pollution

info:eu-repo/semantics/nonPublishe

The Asian side of the world - II

Asia and the Pacific, an immense region, both new and old, in which two thirds of the world lives. A region of superlatives, exceptions, China, continually facing disasters and risks from its past, India, a continent of its own, Japan, archipelago of the future. It is a region that is attracting global growth and becoming the centre of the world. Who could have predicted that the GDP of Asia and the Pacific would be equal to that of the European Union? And what will tomorrow bring? This compilation gives an overview of Asia's world, bringing together texts written by researchers and specialists and that have been published on Asia and the Pacific Network's website (CNRS) between 2011 and 2013. It follows the first volume published in 2011 covering the period 2002-2011. These works covering the humanities and social science recount the past, tell us of the future and illustrate the complexity of Asia and the Pacific through its flaws, strengths and challenges. They reveal the profound roots and depth of the dynamism of these new powers that could soon take over the future of humanity. Numerous researchers and academics specialising in contemporary Asia and the Pacific are bringing into light many aspects of this great and inevitable shift in the world

Interactions aérosols- rayonnement-climat en région méditerranéenne Impact de l'effet radiatif direct sur le cycle de l'eau

International audienceAn experimental campaign, coupled with three-dimensional modeling, was conducted in the western Mediterranean during the summer of 2013 to study the impact of aerosols on the radiative balance and climate of this region. In situ observations were obtained on the ground, aboard two research aircraft and balloons to characterize the physico-chemical and optical properties of particles and their vertical stratification. This campaign was mainly characterized by moderate events of desert aerosols. During these episodes, strong vertical stratification was observed and the measurements of the optical properties reveal moderate absorbing particles in the visible spectrum. Climate simulations indicate a significant impact of aerosols in particular by changing the surface temperature of the sea, the ocean-atmosphere fluxes and consequently seasonal precipitation.Une grande campagne expérimentale a été réalisée en Méditerranée occidentale pendant l'été 2013 afin d'étudier l'impact des aérosols sur le bilan radiatif et le climat régional. Les observations obtenues dans plusieurs stations de surface, à bord de deux avions de recherche, sous ballons sondes plafonnants et par satellite ont documenté la distribution et les propriétés physicochimiques et optiques des particules. Cette campagne a vu se succéder des transports d'aérosols désertiques d'intensité modérée, absorbant modérément le rayonnement solaire et stratifiés verticalement. Les premières simulations climatiques indiquent un impact significatif des aérosols notamment sur la température de surface de la mer, les flux océan-atmosphère et les précipitations saisonnières