Simulations of ARGO profilers and of surface floating objects: applications in MFSTEP

International audienceIn this work we describe part of the activities performed in the MFSTEP project by means of numerical simulations of ARGO profilers and surface floating objects. Simulations of ARGO floats were used to define the optimal time cycling characteristics of the profilers to maximize independent observations of vertical profiles of temperature and salinity and to minimize the error on the estimate of the velocity at the parking depth of the profilers. Instead, the Mediterranean Forecasting System archive of Eulerian velocity field from 2000 to 2004 was used to build a related surface Lagrangian archive, systematically integrating numerical particles released and constrained to drift at surface. Such Lagrangian archive is then used to study the variability of the surface Lagrangian dispersion. Finally, as an example of a possible more realistic application, we estimated the interannual variability of the Lagrangian transport in two key areas of the Western Mediterranean also introducing an exponential decay in the particles concentration

Sensitivity of the Mediterranean circulation to horizontal space-time–dependent tracer diffusivity field in a OGCM

The sensitivity of the Mediterranean circulation to the variability of the horizontal mixing is investigated using a Bryan-Cox–type general circulation model (OGCM). Attention is focused on a parameterisation of mixing previously developed in the context of two-dimensional turbulence, that is for the first time implemented in a OGCM. This parameterisation is suitable for velocity fields characterised by the presence of geostrophic coherent structures, and it is a direct application of the well-known Taylor’s dispersion relation. Theoretical and experimental justifications of the parameterisation are discussed and results from four numerical experiments, with different tracer mixing schemes, are presented. In particular, it is shown that the proposed diffusivity parameterisation improves the tracers transport due to large eddy dynamics and, ensuring a more correct salt budget in the North western part of the basin, contributes to maintain a realistic vertical stratification and winter deep convection in long climatic integrations

CD90/Thy-1 is preferentially expressed on blast cells of high risk acute myeloid leukaemias

Different transformation mechanisms have been proposed for elderly acute myeloid leukaemia (AML) and secondary AML (sAML) when compared with de novo AML or AML of younger patients. However, little is known regarding differences in the immunophenotypic profile of blast cells in these diseases. We systematically analysed, by flow cytometry, 148 patients affected by de novo (100 cases) or sAML (48 cases). By defining a cut-off level of 20% of CD34+ cells co-expressing CD90, the frequency of CD90+ cases was higher in sAML (40%) versus de novo AML (6%, P < 0.001), elderly AML (>60 years) (24%) versus AML of younger patients (10%, P = 0.010) and poor- versus good-risk karyotypes (according to the Medical Research Council classification, P < 0.001). The correlation between CD90 expression, sAML and unfavourable karyotypes was confirmed by analysing the subset of CD34+ AML cases alone (91/148). Consistently, univariate analysis showed that expression of CD90 was statistically relevant in predicting a shorter survival in CD90+ AML patients (P = 0.042). Our results, demonstrating CD90 expression in AML with unfavourable clinical and biological features, suggest an origin of these diseases from a CD90-expressing haemopoietic progenitor and indicate the use of CD90 as an additional marker of prognostic value in AML

Assessment of the impact of TS assimilation from ARGO floats in the Mediterranean Sea

International audienceIn this paper, the impact of assimilating Temperature (T) and Salinity (S) profiles from Argo floats in the Mediterranean Sea (MEDARGO) is quantitatively investigated using the Observing System Simulation Experiments (OSSE) approach. The impact of varying the number of floats and their launch positions is considered, using numerical simulations with a MOM model and a reduced-order multivariate Optimal Interpolation scheme (SOFA) for assimilation. Realistic launch positions used during the first MFSTEP phase are considered, as well as ''ideal'' positions that can be envisioned for the future, along the VOS tracks. The most effective float trajectories are identified, showing that frontal regions play a major role, and that it is crucial to maintain a sufficient coverage of them. In addition to this, also a qualitative comparison is performed between the results obtained from MEDARGO floats in ideal conditions and results from ''ideal'' profiles taken along the VOS (Volunteer Observing Ships) tracks, as for the XBT (Expandable Baththermograph) data