Enhanced MEMS-IMU/odometer/GPS integration using mixture particle filter

Dead reckoning techniques such as inertial navigation and odometry are integrated with GPS to avoid interruption of navigation solutions due to lack of visible satellites. A common method to achieve a low-cost navigation solution for land vehicles is to use a MEMS-based inertial measurement unit (IMU) for integration with GPS. This integration is traditionally accomplished by means of a Kalman filter (KF). Due to the significant inherent errors of MEMS inertial sensors and their time-varying changes, which are difficult to model, severe position error growth happens during GPS outages. The positional accuracy provided by the KF is limited by its linearized models. A Particle filter (PF), being a nonlinear technique, can accommodate for arbitrary inertial sensor characteristics and motion dynamics. An enhanced version of the PF, called Mixture PF, is employed in this paper. It samples from both the prior importance density and the observation likelihood, leading to an improved performance. Furthermore, in order to enhance the performance of MEMS-based IMU/GPS integration during GPS outages, the use of pitch and roll calculated from the longitudinal and transversal accelerometers together with the odometer data as a measurement update is proposed in this paper. These updates aid the IMU and limit the positional error growth caused by two horizontal gyroscopes, which are a major source of error during GPS outages. The performance of the proposed method is examined on road trajectories, and results are compared to the three different KF-based solutions. The proposed Mixture PF with velocity, pitch, and roll updates outperformed all the other solutions and exhibited an average improvement of approximately 64% over KF with the same updates, about 85% over KF with velocity updates only, and around 95% over KF without any updates during GPS outages.     

An Observation Operator for Radar Refractivity Change: Comparison of Observations and Convective-Scale Simulations

Weather radar refractivity depends on low-level moisture, temperature, and pressure and is available at high space–time resolutions over large areas. It is of definite meteorological interest for assimilation, verification, and process-study purposes. In this study, the path-averaged refractivity change is simulated from the Arome cloud-resolving atmospheric system analyses and compared with corresponding radar observations over a 35-day period with various meteorological conditions. For that, a novel post-processing procedure is applied to radar data to improve its quality. Also, an observation operator is developed that ingests Arome analyses and simulates a 3-h path-averaged refractivity change. A sensitivity study shows that simulated path-averaged refractivity change is immune to the modelling of the beam height as long as it remains below approximately 60 m above the ground. Comparisons show overall consistency between observed and simulated path-averaged refractivity change, with discrepancies at times that suggest an improvement in analyses once radar refractivity change observations are assimilated. Finally, errors introduced when retrieving local refractivity from path-averaged refractivity are estimated and it is found for our dataset that such retrievals halve the range of usable observations.     

Recent climatic trends in the tropical Atlantic

A homogeneous monthly data set of sea surface temperature (SST) and pseudo wind stress based on in situ observations is used to investigate the climatic trends over the tropical Atlantic during the last five decades (1964–2012). After a decrease of SST by about 1 °C during 1964–1975, most apparent in the northern tropical region, the entire tropical basin warmed up. That warming was the most substantial (>1 °C) in the eastern tropical ocean and in the longitudinal band of the intertropical convergence zone. Surprisingly, the trade wind system also strengthened over the peirod 1964–2012. Complementary information extracted from other observational data sources confirms the simultaneity of SST warming and the strengthening of the surface winds. Examining data sets of surface heat flux during the last few decades for the same region, we find that the SST warming was not a consequence of atmospheric heat flux forcing. Conversely, we suggest that long-term SST warming drives changes in atmosphere parameters at the sea surface, most notably an increase in latent heat flux, and that an acceleration of the hydrological cycle induces a strengthening of the trade winds and an acceleration of the Hadley circulation. These trends are also accompanied by rising sea levels and upper ocean heat content over similar multi-decadal time scales in the tropical Atlantic. Though more work is needed to fully understand these long term trends, especially what happens from the mid-1970’s, it is likely that changes in ocean circulation involving some combination of the Atlantic meridional overtuning circulation and the subtropical cells are required to explain the observations.     

What’s Hiding Behind Ontogenetic δ<Superscript>13</Superscript>C Variations in Mollusk Shells? New Insights from the Great Scallop (<Emphasis Type="Italic">Pecten maximus</Emphasis>)

Mollusk shells contain geochemical information about environmental conditions that prevailed at the time of formation. We investigated ontogenetic and seasonal variations of δ¹³C in calcitic shells of Pecten maximus. Ontogenetic variations of δ¹³C_shell in three large specimens collected in Norway, France, and Spain exhibited a similar linear decrease with increasing shell height. We removed this linear drift (detrending). These three residual time series displayed variations that could be linked to environmental fluctuations. To check it, we reanalyzed the isotopic datasets of Lorrain et al. (Journal of Experimental Marine Biology and Ecology 275:47–61, 2002, Geochimica et Cosmochimica Acta 68:3509–3519, 2004), who worked on three scallops harvested in 2000 in the bay of Brest (France), a well-monitored ecosystem. Lowest values of δ¹³C_{shell detrended} were recorded in all shells in late spring–early summer, most likely reflecting corresponding variations in food availability. Our results indicate that ontogenetic and seasonal variations of δ¹³C_shell cannot be used as a proxy for past δ¹³C_DIC variations but should be considered as promising tools for ecophysiological studies.     

Otolith reading and multi-model inference for improved estimation of age and growth in the gilthead seabream Sparus aurata (L.)

Accurate knowledge of fish age and growth is crucial for species conservation and management of exploited marine stocks. In exploited species, age estimation based on otolith reading is routinely used for building growth curves that are used to implement fishery management models. However, the universal fit of the von Bertalanffy growth function (VBGF) on data from commercial landings can lead to uncertainty in growth parameter inference, preventing accurate comparison of growth-based history traits between fish populations. In the present paper, we used a comprehensive annual sample of wild gilthead seabream (Sparus aurata L.) in the Gulf of Lions (France, NW Mediterranean) to test a methodology improving growth modelling for exploited fish populations. After validating the timing for otolith annual increment formation for all life stages, a comprehensive set of growth models (including VBGF) were fitted to the obtained age–length data, used as a whole or sub-divided between group 0 individuals and those coming from commercial landings (ages 1–6). Comparisons in growth model accuracy based on Akaike Information Criterion allowed assessment of the best model for each dataset and, when no model correctly fitted the data, a multi-model inference (MMI) based on model averaging was carried out. The results provided evidence that growth parameters inferred with VBGF must be used with high caution. Hence, VBGF turned to be among the less accurate for growth prediction irrespective of the dataset and its fit to the whole population, the juvenile or the adult datasets provided different growth parameters. The best models for growth prediction were the Tanaka model, for group 0 juveniles, and the MMI, for the older fish, confirming that growth differs substantially between juveniles and adults. All asymptotic models failed to correctly describe the growth of adult S. aurata, probably because of the poor representation of old individuals in the dataset. Multi-model inference associated with separate analysis of juveniles and adult fish is then advised to obtain objective estimations of growth parameters when sampling cannot be corrected towards older fish.     

Growth of the European abalone (Haliotis tuberculata L.) in situ: Seasonality and ageing using stable oxygen isotopes

The ormer, Haliotis tuberculata is the only European abalone species commercially exploited. The determination of growth and age in the wild is an important tool for fisheries and aquaculture management. However, the ageing technique used in the past in the field is unreliable. The stable oxygen isotope composition (¹⁸O/¹⁶O) of the shell depends on the temperature and oxygen isotope composition of the ambient sea water. The stable oxygen isotope technique, developed to study paleoclimatological changes in shellfish, was applied to three H. tuberculata specimens collected in north-west Brittany. For the specimens collected, the oxygen isotope ratios of the shell reflected the seasonal cycle in the temperature. From winter-to-winter cycles, estimates of the age and the annual growth increment, ranging from 13 to 55 mm per year were obtained. This study shows that stable oxygen isotopes can be a reliable tool for ageing and growth studies of this abalone species in the wild, and for validating other estimates.     

Volatile (sulphur and chlorine), major,and trace element geochemistry of mafic to intermediate tephras from the Chilean Southern Volcanic Zone (33–43°S)

Here we present the first systematic investigation of volatile geochemistry along the Southern Volcanic Zone (SVZ) of Chile. Holocene olivine-hosted melt inclusions in the most mafic tephras sampled from 16 volcanoes along the volcanic front of the SVZ between 33°S and 43°S were analysed for pre-eruptive sulphur, chlorine, and major element contents. These results are combined with trace element compositions of the host whole rocks. The highest fractionation-corrected gas contents occur in the least-degassed melt inclusions from small monogenetic cones of Los Hornitos, Cabeza de Vaca, and Apagado from both the transitional and the southern-central SVZ, reaching ~3,000 μg/g S and 1,400 μg/g Cl, while the lowest abundances of ~1,100 μg/g S and ~600 μg/g Cl were found in the central SVZ at Volcán Lonquimay, Volcán Llaima, and Volcán Villarrica. Chlorine co-varies with trace element indicators for the degree of melting and/or source enrichment, such that the lowest Cl contents are found in high-degree melts from the most depleted mantle sources. The size of the volcanic edifices correlates inversely with Cl abundances in the melt. This could reflect more extensive degassing during ascent through the complex magma plumbing systems beneath the stratovolcanoes or greater dilution during larger degrees of melting of more depleted sources, or a combination of these factors. Compared to other subduction zones, the SVZ melt inclusions exhibit Cl and S abundances in the same range as most of those from the Central American and those from the Marianas arcs.     

http://www.sciencedirect.com/science/article/pii/S167498711400005X

Recalling some of the most important events and persons during his education and career, the author sketches his growth from a young engineer, educated in the sanctuary of solid state reactions, to an involved fully devoted scientific career for the study of fluids in the deep Earth. Most important in this respect was the discovery of C02 inclusions in granulites, which triggered years of discussion on fluid- absent or fluid-assisted granulite metamorphism. To some extent, this debate is a continuation of the former granite controversy, but it shows also how the famous battle of ＂soaks against pontiffs＂ could have been easily avoided.     

http://www.sciencedirect.com/science/article/pii/S1674987114000590

This paper reviews the origin and evolution of fluid inclusions in ultramafic xenoliths,providing a framework for interpreting the chemistry of mantle fluids in the different geodynamic settings.Fluid inclusion data show that in the shallow mantle,at depths below about 100 km,the dominant fluid phase is CO_2±brines,changing to alkali-,carbonate-rich(silicate) melts at higher pressures.Major solutes in aqueous fluids are chlorides,silica and alkalis(saline brines;5-50 wt.%NaCl eq.).Fluid inclusions in peridotites record CO_2 fluxing from reacting metasomatic carbonate-rich melts at high pressures,and suggest significant upper-mantle carbon outgassing over time.Mantle-derived CO_2(±brines) may eventually reach upper-crustal levels,including the atmosphere,independently from,and additionally to magma degassing in active volcanoes.