1,721,090 research outputs found
Le piante aromatiche in Sicilia
No full textLes plantes aromatiques sont toutes les espéces vegetales caractérisées par avoir des substances volatiles parfumées traditionnelement utilisées pour aromatiser les aliments ou les produits pharmaceutiques ou cosmétiques. Beaucoup des espéces aromatiques ont aussi des différentes propriétés spécifique (antioxydants, colorants, thérapeutique) qui les rendent attrayants pour de nombreux secteurs de l'industrie. La flore naturelle sicilienne se compose de plusieurs des espécés avec ces caractéristiques et leur culture sur de superficies moyen-large peuvent contribuer à la création de nouvelles sources de revenus supplémentaire pour des environnements marginaux. Dans ce but il faut affiner des aspects agronomiques comme les faible niveau de mécanisation des cultures et leur réduite réponse à la technologie plus usuel
Stochastic resonance in two-dimensional Landau Ginzburg equation
No full textWe study the mechanism of stochastic resonance for the Landau Ginzburg equation in two space dimensions, perturbed by a white noise. We review how to renormalize the equation in order to avoid ultraviolet divergences. Next, we show that the renormalization amplifies the effect of the small periodic perturbation in the system. We argue that stochastic resonance can be used to highlight the effect of renormalization in a spatially extended system with multiple, stable statistical steady states
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Formula for a baroclinic adjustment theory of climate
No full textRecently, a theory relating baroclinic neutrality and midlatitudes tropopause height has been
proposed. However, GCM results have shown that the dependence of the theory on external
parameters is not consistent with that displayed by these numerical experiments. In the present
paper we suggest an analytic formula for baroclinic adjustment to the neutrality of Eady waves
through tropopause modification. This formula extends considerably the abovementioned
theory by taking into account both a simple representation of the stratosphere and the topography.
These modifications alter the tropopause condition for a baroclinically neutral state
and its sensitivity to the external parameters. In particular, the topography introduces a dependence
on the tropospheric vertical wind shear of the neutrality condition. This feature is not
present in other models that assume a background state with a zero potential vorticity gradient
in the troposphere.We show, furthermore, that the modified neutrality condition has sensitivities that may resemble those displayed by GCM simulations, with respect to the parameters defining the background flow
The analysis of the standardized precipitation index in the mediterranean area: large-scale patterns
No full textLarge-scale assessment of drought variability based on NCEP/NCAR and ERA-40 re-analyses
No full textThe impacts of different spatial resolutions and different data assimilation schemes of the available re-analysis data sets (NCEP/NCAR and ERA-40) on the assessment of drought variability are analysed. Particular attention has been devoted to the analysis of the possible existence of a linear trend in the climatic signal. The long-term aspects of drought over the globe during the last forty years have been evaluated by computing the Standardized Precipitation Index (SPI) on 24-month time scale. The SPI, in fact, seems to be a useful tool for monitoring dry and wet periods on multiple time scales and comparing climatic conditions of areas governed by different hydrological regimes. To unveil possible discrepancies between the analyses carried out with the two data sets, we studied the leading space-time variability of drought by applying the principal component analysis (PCA) to the SPI time series. Results suggest that on the global scale, the two re-analyses agree in their first principal component score, but not in the associated loading: both re-analyses capture a linear trend, though the areas where this feature should be most likely observed are not uniquely identified by the two data sets. Moreover, while the ERA-40 unveils the presence of a weak net 'global' trend towards wet conditions, the NCEP/NCAR re-analysis suggests that the areas in the world characterised by positive/negative trends balance to zero. At large regional scale, a good agreement of the results with those obtained from the observations are found for the United Stated, while for the European sector the two re-analyses show remarkable differences both in the first loading and in representing the timing of the wet and dry periods. Also for these areas a linear trend, superposed on other short-term fluctuations, is detectable in the first principal component of the SPI field. © Springer Science+Business Media B.V. 2006
Interannual variability of stratospheric ozone and temperature in response to 11-year solar cycle: FFT andWavelet Coherence Analysis
No full textThe interannual variability of stratospheric ozone mass mixing ratio (O3) and temperature (T) from 1979 to 2012 is
investigated using the latest ERA-Interim reanalysis product delivered by the European Centre for Medium Range
Weather Forecasts (ECMWF). In particular, the response of the stratosphere to the quasi-eleven solar activity cycle
is investigated using the Mg II Index time series for the common time section.
Results reveal the following features: (i) Upward (downward) trends characterize zonally averaged O3 anomalies
in the upper (middle-lower) stratosphere, while prevailing downward trends affect the T field. Mg II Index shows a
downward trend mainly driven by the 24th cycle that is weaker compared with the previous two; (ii) Correlations
between O3 and Mg II, T and Mg II, and O3 and T are consistent with photochemical reactions occurring in the
stratosphere and large-scale transports; (iii) The FFT analysis of zonally averaged O3 anomalies reveal a periodicity
of 11.3 year in the upper and middle stratosphere, which disappears near the tropopause level (100 hPa); (iv) The
Wavelet cross-spectra and coherence between O3 and Mg II Index show common power at near-11 year periodicity
and different relative phase shift in the upper and middle stratosphere
Sensitivity of cloud radiative forcing to changes of microphysical parameters measured by the CLOUDS mission
No full textCLOUDS (a Cloud and Radiation monitoring satellite) is a study for a satellite mission designed to provide the gross vertical profile, the internal structure. the radiative and the imaging features of clouds. This subject is addressed by several missions designed for process study intent. CLOUDS, instead, is designed for providing data of routine use in long-term Numerical Weather Prediction (NWP) and General Circulation Model (GCM). User requirements have been collected from various sources, and instruments concepts derived to meet those requirements. However, to establish the sensitivity of a GCM to the targeted parameters and confirm the soundness of the specified requirements (mainly accuracy and vertical resolution), special effort had to be placed. The present paper offers a rather complete assessment of the range of usefulness that CLOUDS measurements may have on the radiative calculation. To this purpose, the cloud forcing was computed as a function of cloud parameters by using a radiative model that has been applied in the GCM of the Laboratory for Atmospheres at the NASA Goddard Space Flight Center. The results show that, in most cases, the model response to the addressed cloud parameters is good if the error is within the specified limit. This is better demonstrated for relatively large particle sizes, for ice better than for liquid water, for low optical thickness and for low cloud cover. The model, however, suggests that more stringent requirements would be appropriate when small particles are considered
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