Space and Time Occurrence of Algal Blooms in the Mediterranean: their Significance for the Trophic Regime of the Basin

The Mediterranean Sea is generally classified as an oligotrophic basin with a dominant subtropical regime. The coarse temporal resolution of the Coastal Zone Color Scanner data did not allow to properly reconstruct the dynamics of the regional events which could support or falsify that view. In this thesis, five years of the SeaWiFS Mediterranean data were analyzed to depict the trophic regime of the basin and to quantify the impact of periodic or episodic phytoplankton blooms occurring there. The retrieval of chlorophyll a concentration was based on a new empirical regional algorithm (DORMA) developed and tested in the frame of this study. While confirming the low standing stock of phytoplankton biomass evidenced by the CZCS time series, the SeaWiFS imageries allowed to discriminate among two distinct regimes, which were classified as the ‘bloom areas’ and ‘non-bloom areas’. The former are mostly driven by the coupling of local atmospheric forcing and cyclonic circulation and, therefore, are often sites of dense water formation whereas the latter do follow a typical sub-tropical seasonal cycle without a pronounced maximum of biomass over the year. Surprisingly, the second regime not only pertains to most of the Eastern basin, as previously assumed, but also to the southern part of the Western one. The ‘bloom areas’ contribute to no more than 10-15% of the primary production in the basin, but account for the relevant part of the interannual variability in the standing stock of autotrophic biomass and display a seasonal cycle close to the North Atlantic Drift Region (sensu Longhurst). The merge of atmospheric data, 1D modeling and remote sensed SST as well as color water leaving radiances also allowed a detailed reconstruction of the dynamics of each bloom site and of the impact of the climatic fluctuation, usually referred as the eastern Mediterranean Transect, which took place at the beginning of the nineties in the basin

Ask a question! How Italian children with cochlear implants produce subject and object wh- questions

Syntax is impaired in individuals with cochlear implants (CIs). Several studies have shown that Italian speaking children fitted with CIs have troubles with relative clauses (Volpato & Adani 2009; Volpato 2010; Volpato 2012; Volpato & Vernice 2014), sentences containing clitic pronouns (Guasti et al. 2014), and wh-questions (Volpato & D’Ortenzio 2017). The aim of this study is to provide a detailed analysis of the production of wh-questions by a group of 13 Italian-speaking children fitted with CIs, and to compare their performance with a group of 13 typically developing children matched on comparable chronological age. Accuracy is lower in the group of children with CIs than in controls, but no significant difference was found between the two groups. However, much individual variability was observed. Some children with CIs showed good competence of Italian. Other children produce ungrammatical sentences, which is evidence of the linguistic delay associated to hearing impairment, even when they are fitted with CI

Observation of mixed anisotropy in the critical susceptibility of an ultrathin magnetic film

Measurements of the magnetic susceptibility of Fe/W(110) films with thickness in the range of 1.6 to 2.4 ML Fe, show that in addition to the large response along the easy axis associated with the Curie transition, there is a much smaller, paramagnetic hard axis response that is not consistent with the 2D anisotropic Heisenberg model used to describe homogeneous in-plane ferromagnets with uniaxial anisotropy. The shape, amplitude, and peak temperature of the hard axis susceptibility, as well as its dependence upon layer completion close to 2.0 ML, indicate that inhomogeneities in the films create a system of mixed anisotropy. A likely candidate for inhomogeneities that are magnetically relevant in the critical region are the closed lines of step edges associated with the incomplete layers. According to the Harris criterion, the existence of magnetically relevant inhomogeneities may alter the critical properties of the films from those of a 2D Ising model. Experiments in the recent literature are discussed in this context.Comment: 9 two-column pages, 6 figures. This replacement has a new title and abstract, and one additional figur

Adaptive mixture approximation for target tracking in clutter

Target tracking represents a state estimation problem recurrent in many practical scenarios like air traffic control, autonomous vehicles, marine radar surveillance and so on. In a Bayesian perspective, when phenomena like clutter are present, the vast majority of the existing tracking algorithms have to deal with association hypotheses which can grow in the number over time; in that case, the posterior state distribution can become computationally intractable and approximations have to be introduced. In this work, the impact of the number of hypotheses and corresponding reductions is investigated both in terms of employed computational resources and tracking performances. For this purpose, a recently developed adaptive mixture model reduction algorithm is considered in order to assess its performances when applied to the problem of single object tracking in the presence of clutter and to provide additional insights on the addressed problem

Phytoplankton biomass cycles in the North Atlantic subpolar gyre: A similar mechanism for two different blooms in the Labrador Sea

An analysis of seasonal variations in climatological surface chlorophyll points to distinct biogeographical zones in the North Atlantic subpolar gyre. In particular, the Labrador Sea appears well delineated into two regions on either side of the 60°N parallel, with very different climatological phytoplankton biomass cycles. Indeed, north of 60°N, an early and short spring bloom occurs in late April, while south of 60°N, the bloom gradually develops 1 month later and significant biomass persists all summer long. Nevertheless, at climatological scale, the first-order mechanism that controls the bloom is identical for both bioregions. The light-mixing regime can explain the bloom onset in both bioregions. In the Labrador Sea, the blooms seem to rely on a mean community compensation irradiance threshold value of 2.5 mol photon m−2 d−1 over the mixed layer

Towards a merged satellite and in situ fluorescence ocean chlorophyll product

Understanding the ocean carbon cycle requires a precise assessment of phytoplankton biomass in the oceans. In terms of numbers of observations, satellite data represent the largest available data set. However, as they are limited to surface waters, they have to be merged with in situ observations. Amongst the in situ data, fluorescence profiles constitute the greatest data set available, because fluorometers have operated routinely on oceanographic cruises since the 1970s. Nevertheless, fluorescence is only a proxy of the total chlorophyll <i>a</i> concentration and a data calibration is required. Calibration issues are, however, sources of uncertainty, and they have prevented a systematic and wide range exploitation of the fluorescence data set. In particular, very few attempts to standardize the fluorescence databases have been made. Consequently, merged estimations with other data sources (e.g. satellite) are lacking. <br><br> We propose a merging method to fill this gap. It consists firstly in adjusting the fluorescence profile to impose a zero chlorophyll <i>a</i> concentration at depth. Secondly, each point of the fluorescence profile is then multiplied by a correction coefficient, which forces the chlorophyll <i>a</i> integrated content measured on the fluorescence profile to be consistent with the concomitant ocean colour observation. The method is close to the approach proposed by Boss et al. (2008) to correct fluorescence data of a profiling float, although important differences do exist. To develop and test our approach, in situ data from three open ocean stations (BATS, HOT and DYFAMED) were used. Comparison of the so-called "satellite-corrected" fluorescence profiles with concomitant bottle-derived estimations of chlorophyll <i>a</i> concentration was performed to evaluate the final error (estimated at 31%). Comparison with the Boss et al. (2008) method, using a subset of the DYFAMED data set, demonstrated that the methods have similar accuracy. The method was applied to two different data sets to demonstrate its utility. Using fluorescence profiles at BATS, we show that the integration of "satellite-corrected" fluorescence profiles in chlorophyll <i>a</i> climatologies could improve both the statistical relevance of chlorophyll <i>a</i> averages and the vertical structure of the chlorophyll <i>a</i> field. We also show that our method could be efficiently used to process, within near-real time, profiles obtained by a fluorometer deployed on autonomous platforms, in our case a bio-optical profiling float. The application of the proposed method should provide a first step towards the generation of a merged satellite/fluorescence chlorophyll <i>a</i> product, as the "satellite-corrected" profiles should then be consistent with satellite observations. Improved climatologies with more consistent satellite and in situ data are likely to enhance the performance of present biogeochemical models

A Collaborative Decision Environment for UAV Operations

NASA is developing Intelligent Mission Management (IMM) technology for science missions employing long endurance unmanned aerial vehicles (UAV's). The IMM groundbased component is the Collaborative Decision Environment (CDE), a ground system that provides the Mission/Science team with situational awareness, collaboration, and decisionmaking tools. The CDE is used for pre-flight planning, mission monitoring, and visualization of acquired data. It integrates external data products used for planning and executing a mission, such as weather, satellite data products, and topographic maps by leveraging established and emerging Open Geospatial Consortium (OGC) standards to acquire external data products via the Internet, and an industry standard geographic information system (GIs) toolkit for visualization As a Science/Mission team may be geographically dispersed, the CDE is capable of providing access to remote users across wide area networks using Web Services technology. A prototype CDE is being developed for an instrument checkout flight on a manned aircraft in the fall of 2005, in preparation for a full deployment in support of the US Forest Service and NASA Ames Western States Fire Mission in 2006

The production of relative clauses by Italian cochlear-implanted and hearing children

This study investigates the elicited production of subject (SRs) and object relatives (ORs) in Italian by 13 cochlear-implanted (CI) children (age:7;9-10;8) to determine whether and to what extent they differ from three groups of 13 normal hearing (NH) children matched on morphosyntactic abilities (age:5;0-7;9), chronological age (age:7;5-10;3), and auditory age (e.g. duration of CI use (age:4;11-9;4)) respectively. Results showed that for CI children, SRs are more accurate than ORs. The same asymmetry is observed in all NH groups, although NH children’s percentages of target responses are higher for both sentence typologies. The syntactic difficulty with ORs led CI and NH groups to adopt a considerable number of answering strategies: among them, production of passive relatives, causative constructions, and wh- elements replacing the complementizer che (‘that’). Individual performance variability within the CI group is observed. Some CI children showed good competence in Italian and age-peer performance by producing passive relatives, which are largely attested in older children’s production. For other CI children, however, the tendency to produce sentences attested in young children’s production is evidence of the linguistic delay associated to hearing impairment. In this case, the performance of these CI children was comparable to that of younger NH children

L’uso del test di ripetizione per la valutazione della competenza sintattica del bambino sordo con impianto cocleare

Reduced language inputs due to hearing loss can affect the development of syntactically complex structures derived by syntactic movement. Cochlear implants (CIs) can provide proper linguistic input to children with severe to profound sensorineural hearing loss. However, despite an early diagnosis and intervention, and the development of lexical skills and speech perception similar to typically developing age peers, children with CIs still show a delay in processing movement-derived structures. Following previous studies on deaf or hard-of-hearing Hebrew, and German-speaking children, this study provides first data on the repetition of movement-derived syntactically complex structures in Italian-speaking children with CIs. Indeed, as shown by previous studies, resorting to a sentence repetition task allow to analyse both the participant’s ability in analysing structures derived by movement and their memory skills. It also allows to exclude memory as the cause of misinterpretation of the stimuli. Results showed that children with CIs performed poorer than their typically developing age peers and showed many difficulties in all the structures characterized by a complex derivation. Interestingly, both groups showed several difficulties in the production of oblique prepositional and genitive relative clauses

Correction of profiles of in-situ chlorophyll fluorometry for the contribution of fluorescence originating from non-algal matter

In situ chlorophyll fluorometers have been widely employed for more than half a century, and to date, it still remains the most used instrument to estimate chlorophyll-a concentration in the field, especially for measurements onboard autonomous observation platforms, e.g., Bio-Argo floats and gliders. However, in deep waters (> 300 m) of some specific regions, e.g., subtropical gyres and the Black Sea, the chlorophyll fluorescence profiles frequently reveal “deep sea red fluorescence” features. In line with previous studies and through the analysis of a large data set (cruise transect in the South East Pacific and data acquired by 82 Bio- Argo floats), we show that the fluorescence signal measured by a humic-like DOM fluorometer is highly correlated to the “deep sea red fluorescence.” Both fluorescence signals are indeed linearly related in deep waters. To remove the contribution of non-algal organic matter from chlorophyll fluorescence profiles, we introduce a new correction. Rather that removing a constant value (generally the deepest chlorophyll a fluorescence value from the profile, i.e., so-called “deep-offset correction”), we propose a correction method which relies on DOM fluorometry and on its variation with depth. This new method is validated with chlorophyll concentration extracted from water samples and further applied on the Bio-Argo float data set. More generally, we discuss the potential of the proposed method to become a standard and routine procedure in quality-control and correction of chlorophyll a fluorescence originating from Bio-Argo network