ALBERT

Description: The Mediterranean community represented in this paper is the result of more than 30 years of EU and nationally funded coordination, which has led to key contributions in science concepts and operational initiatives. Together with the establishment of operational services, the community has coordinated with universities, research centers, research infrastructures and private companies to implement advanced multi-platform and integrated observing and forecasting systems that facilitate the advancement of operational services, scientific achievements and mission-oriented innovation. Thus, the community can respond to societal challenges and stakeholders needs, developing a variety of fit-for-purpose services such as the Copernicus Marine Service. The combination of state-of-the-art observations and forecasting provides new opportunities for downstream services in response to the needs of the heavily populated Mediterranean coastal areas and to climate change. The challenge over the next decade is to sustain ocean observations within the research community, to monitor the variability at small scales, e.g., the mesoscale/submesoscale, to resolve the sub-basin/seasonal and inter-annual variability in the circulation, and thus establish the decadal variability, understand and correct the model-associated biases and to enhance model-data integration and ensemble forecasting for uncertainty estimation. Better knowledge and understanding of the level of Mediterranean variability will enable a subsequent evaluation of the impacts and mitigation of the effect of human activities and climate change on the biodiversity and the ecosystem, which will support environmental assessments and decisions. Further challenges include extending the science-based added-value products into societal relevant downstream services and engaging with communities to build initiatives that will contribute to the 2030 Agenda and more specifically to SDG14 and the UN's Decade of Ocean Science for sustainable development, by this contributing to bridge the science-policy gap. The Mediterranean observing and forecasting capacity was built on the basis of community best practices in monitoring and modeling, and can serve as a basis for the development of an integrated global ocean observing system.

Description: Dada la importancia que revisten los suelos en los procesos que ocurren en la zona crítica (zona de interacción entre agua, suelo, aire, organismos), en este trabajo presentamos la distribución temporal y espacial de una secuencia de paleosuelos arcillosos con carbonatos secundarios (capas de caliches y carbonatos diseminados) en el sector nororiental de la Cuenca de México, particularmente en el valle de Teotihuacán. El propósito de este trabajo consiste en reconstruir la distribución temporal y espacial de la cubierta de suelos del pasado para entender su relación con la estructura actual de suelos y sedimentos en este sector semiárido de la cuenca de México. Con esta información, determinar la participación de estos materiales en la Zona Crítica (ZC). Para ello, se ha llevado a cabo un transecto de dirección norte-sur, que inicia en las elevaciones del Cerro Gordo, cruza el valle de Teotihuacán y termina en la Sierra Patlachique, describiendo perfiles de suelo en diferentes posiciones geomorfológicas. El marco cronológico se ha establecido con base en fechamientos de radiocarbono realizados en las capas de caliches. De acuerdo a la cronología, al tipo y grado de pedogénesis, y a los procesos de sedimentación, se han reconocido cuatro unidades. La primera unidad, denominada Paleosuelos del Pleistoceno, fase I (50000 – 20000 años AP), está compuesta de paleosuelos arcillosos, los cuales son Luvisoles crómicos y estágnicos, dependiendo de su posición en el paisaje. Estos paleosuelos muestran tanto carbonatos secundarios diseminados y en fracturas, como capas de caliches. En la segunda unidad, Paleosuelos del Pleistoceno, fase II (20000 –10000 años AP), dominan los sedimentos sobre los suelos; únicamente en el fondo del Valle, se han encontrado Gleysoles cortados por canales aluviales. La unidad, Paleosuelos del Holoceno, fase I (10000 a 1000 años AP) se caracteriza por presentar suelos poligenéticos (Vertisoles), fuertemente modificados por los procesos antrópicos, durante las diversas fases de ocupación pre-hispánica. La última unidad, Suelos del Holoceno, fase II, abarca el último milenio, en donde se destacan procesos de erosión e inestabilidad del paisaje. La tendencia principal en la distribución espacial de los paleosuelos es la siguiente: las unidades antiguas (Luvisoles, capas de caliches y Vertisoles) están sepultadas profundamente en el fondo del valle. Sin embargo, en los taludes y elevaciones montañosas, pueden aparecer cerca o directamente sobre la superficie, siendo incorporados en el manto de suelos actual. Las interrelaciones entre los diferentes paleosuelos a lo largo del transecto estudiado, junto con las observaciones micromorfológicas, apoyan la hipótesis de una relación evolutiva entre los Luvisoles pleistocénicos y los Vertisoles del Holoceno. Consideramos que estas diferentes unidades repercuten en los procesos hidrológicos en el valle y que las capas de caliche formadas en los ambientes pleistocénicos pueden afectar la geoquímica del agua subterránea así como sus firmas isotópicas.

Description: As soils are important elements for the processes involved in the critical zone (the zone of interaction between water, soil, air, and organisms), in this work we present the temporal and spatial distribution of a clayey-paleosol sequence with secondary carbonates (layers of caliche and disseminated carbonates) in the northeast sector of the Mexico Basin, particularly in the Teotihuacan Valley. The goal of this paper is the temporal and spatial reconstruction of the past soil cover to understand its relationship with the present day soils and sediments in this semiarid sector of the Mexico Basin. With this information the involvement of these materials in the critical zone could be determined. To comply with these objectives, a north-south transect was carried out, starting in the Cerro Gordo, crossing the Teotihuacan valley and ending in the Sierra Patlachique, describing soil profiles located in different geomorphological positions. The chronological framework has been established with radiocarbon dates of the caliche layers. According to this chronology, the type and degree of pedogenesis, as well as the sedimentation processes, four units have been recognized. The first unit is named the Pleistocene Paleosols, phase I (50000 – 20000 years BP), and is composed of clayey paleosols, chromic and stagnic Luvisols, depending on their position in the landscape. These paleosols contain pedogenic carbonates, disseminated and in fractures, and caliche layers. In the second unit, the Pleistocene Paleosols, phase II (20000 –10000 years BP), sediments predominate over soils; only in the valley floor some Gleysols are found to be cut by alluvial channels. The unit, Paleosols of the Holocene Paleosols unit, phase I (10000 to 1000 years BP), is characterized by polygenetic soils (Vertisols) strongly modified by anthropic processes during distinct phases of pre-hispanic occupation. The last unit, the Holocene Soils, phase II, covers the last millennium when erosional processes and unstable landscape dominate. The paleosols (Luvisols, caliche layers, and Vertisols) are deeply buried at the bottom of the valley. However, on the slopes and hilltop positions, they can appear close to or directly on the surface, being incorporated in the present day soil mantle. Spatial interrelations of different paleosols along the studied transect together with micromorphological observations support the hypothesis of an evolutionary link between the Pleistocene Luvisols and the Holocene Vertisols. We propose that these different units are involved in the hydrological processes in the valley and that the caliche layers, formed in the Pleistocene environments, can affect the geochemistry of the groundwater as well as its isotopic signatures.

Description: Major new computations of terrestrial gravitational field models were performed by the Geodynamics Branch of Goddard Space Flight Center (GSFC). This development has incorporated the present state of the art results in satellite geodesy and have relied upon a more consistent set of reference constants than was heretofore utilized in GSFC's GEM models. The solutions are complete in spherical harmonic coefficients out to degree 50 for the gravity field parameters. These models include adjustment for a subset of 66 ocean tidal coefficients for the long wavelength components of 12 major ocean tides. This tidal adjustment was made in the presence of 550 other fixed ocean tidal terms representing 32 major and minor ocean tides and the Wahr frequency dependent solid earth tidal model. In addition 5-day averaged values for Earth rotation and polar motion were derived for the time period of 1980 onward. Two types of models were computed. These are satellite only models relying exclusively on tracking data and combination models which have incorporated satellite altimetry and surface gravity data. The satellite observational data base consists of over 1100 orbital arcs of data on 31 satellites. A large percentage of these observations were provided by third generation laser stations (less than 5 cm). A calibration of the model accuracy of the GEM-T2 satellite only solution indicated that it was a significant improvement over previous models based solely upon tracking data. The rms geoid error for this field is 110 cm to degree and order 36. This is a major advancement over GEM-T1 whose errors were estimated to be 160 cm. An error propagation using the covariances of the GEM-T2 model for the TOPEX radial orbit component indicates that the rms radial errors are expected to be 12 cm. The combination solution, PGS-3337, is a preliminary effort leading to the development of GEM-T3. PGS-3337 has incorporated global sets of surface gravity data and the Seasat altimetry to produce a model complete to (50,50). A solution for the dynamic ocean topography to degree and order 10 was included as part of this adjustment.

Description: An estimation technique was developed to extrapolate tidal amplitudes and phases over entire ocean basins using existing gauge data and the altimetric measurements provided by satellite oceanography. The technique was previously tested. Some results obtained by using a 3 deg by 3 deg grid are presented. The functions used in the interpolation are the eigenfunctions of the velocity (Proudman functions) which are computed numerically from a knowledge of the basin's bottom topography, the horizontal plan form and the necessary boundary conditions. These functions are characteristic of the particular basin. The gravitational normal modes of the basin are computed as part of the investigation; they are used to obtain the theoretical forced solutions for the tidal constituents. The latter can provide the simulated data for the testing of the method and serve as a guide in choosing the most energetic functions for the interpolation.

Description: Using a simple dynamical model of a wind-driven ocean circulation of the Stommel type, and an analytical basis developed to objectively analyze the sea surface height residuals from an altimeter and, in the process, to determine the total flow instead of just the near surface geostrophic component associated with the given sea surface topography. The method is based on first deriving the solution to the forced problem for a given wind stress required to develop a hypothetical true or perfect data field and to establishing the basis for the objective analysis. The stream function and the surface height field for the forced problem are developed in terms of certain characteristic functions with the same expansion coefficients for both fields. These characteristic functions are simply the solutions for a homogeneous elliptic equation for the stream function and the solutions of an inhomogeneous balance equation for the height field. For the objective analysis, using a sample of randomly selected height values from the true data field, the height field characteristic functions are used to fit the given topography in a least squares sense. The resulting expansion coefficients then permit the synthesis of the total flow field via the stream function characteristic modes and the solution is perfectly well behaved even along the equator. The method of solution is easily adaptable to realistic ocean basis by straight forward numerical methods. The analytical basis of the theory and the results for an ideal rectangular basin on a beta plane are described.

Description: An objective analysis technique has been developed to extrapolate tidal amplitudes and phases over entire ocean basins using existing gauge data and the altimetric measurements which are now beginning to be provided by satellite oceanography. The technique was previously tested in the Lake Superior basin. The method has now been developed and applied in the Atlantic-Indian ocean basins using a 6 deg x 6 deg grid to test its essential features. The functions used in the interpolation are the eigenfunctions of the velocity potential (Proudman functions) which are computed numerically from a knowledge of the basin's bottom topography, the horizontal plan form and the necessary boundary conditions. These functions are characteristic of the particular basin. The gravitational normal modes of the basin are computed as part of the investigation, they are used to obtain the theoretical forced solutions for the tidal constituents, the latter provide the simulated data for the testing of the method and serve as a guide in choosing the most energetic modes for the objective analysis. The results of the objective analysis of the M2 and K1 tidal constituents indicate the possibility of recovering the tidal signal with a degree of accuracy well within the error bounds of present day satellite techniques.

Description: This paper presents the application of a model reference adaptive control (MRAC) algorithm to flexible aircraft flight control. The algorithm is an adaptive version of the Command Generator Tracking (CGT) control technique. This technique forces a dynamic system to follow a reduced-order model, allowing it to cope with the problem of unmodeled dynamics. The studies were made via simulation, using for the plant an aircraft dynamic model similar to the B1 bomber. This model is of a large aircraft with a reasonable amount of structural flexibility. In particular, flight configurations were analyzed where the influence of the flexible modes make it difficult to control the aircraft. The results indicate that the algorithm has good robustness properties vis-a-vis unmodeled dynamics and can force the flexible aircraft to follow rigid body responses.

Description: A high-degree spherical harmonic series is used to compute the radial deformation of the Earth by oceanic tidal loading. By exploiting fast numerical transforms, this approach is found to be much more efficient, but no less accurate, than the traditional Green's function approach. The method is used to derive an atlas of load tide maps for 10 constitutents of the NSWC ocean tide model.

Description: The techniques for computing the eigenfunctions of the velocity potential (Proudman functions) set out in Sanchez, et al. (1986) in relation to the Atlantic-Indian Oceans are here applied to the Pacific Ocean, using a 6x6 degree grid of 510 points (455 points for the associated stream functions). Normal modes are computed from the first Proudman functions and have natural periods from 43.9h downward. Tidal syntheses are derived from these modes by direct application of the (frictionless) dynamic equations and by least-squares fitting of Proudman functions to the dynamically interpolated tide-gauge data of Schwiderski (1983). The modes contributing the most energy to the principal harmonic tidal constituents are different in the two computations: their natural periods are typically in the range of 9 to 16h for semidiurnal, and 14 to 43h for diurnal tides. The rms of fit for the Proudman functions is, in all cases, better than the corresponding value for the same number of spherical harmonics.