arXiv subjects

V. Lucarini

Publications and source records attributed to V. Lucarini.

6 recordsLinked to original sources

arXiv2009

Thermodynamics of Climate Change: Generalized Sensitivities

Using a recently developed formalism, we present an in-depth analysis of how the thermodynamics of the climate system varies with CO2 concentration by performing experiments with a simplified yet Earth-like climate model. We find that, in addition to the globally averaged surface temperature, the intensity of the Lorenz energy cycle, the Carnot efficiency, the entropy production and the degree of irreversibility of the system are linear with the logarithm of the CO2 concentration. The generalized sensitivities proposed here suggest that the climate system becomes less efficient, more irreversible, and features higher entropy production as it becomes warmer.

physics.ao-ph↗

arXiv2006

Discrepancies in Southern Hemisphere Mid-latitude Atmospheric Variability of the NCEP-NCAR and ECMWF Reanalyses

In this study we compare the representation of the southern hemisphere midlatitude winter variability in the NCEP-NCAR and ERA40 reanalyses. We use the classical Hayashi spectral technique, recently applied to compare the description of the atmospheric variability in the northern hemisphere on different spectral sub-domains. We test the agreement of the two reanalysis systems in the representation of the atmospheric activity. In the southern hemisphere, even in the satellite period, the assimilated data are relatively scarce, predominately over the oceans, and they provide a weaker constraint to the model dynamics. We find relevant discrepancies in the description of the variability at different spatial and temporal scales. ERA40 is generally characterised by a larger variance, especially in the high frequency spectral region. In the pre-satellite period the discrepancies between the two reanalyses are large and randomly distributed while after the 1979 the discrepancies are systematic. Moreover, a sudden jump in the VTPR period (1973-1978) is observed, mostly in the ERA40 reanalysis. Our results suggest that today we do not have a well-defined picture of the properties of the winter mid-latitude variability in the southern hemisphere to be used in the evaluation of the realism of climate models and demand for an intercomparison study for the assessment of the self-consistency of the IPCC models in the representation of the analysed properties.

physics.ao-ph↗

arXiv2005

Testing the validity of THz reflection spectra by dispersion relations

Complex response function obtained in reflection spectroscopy at terahertz range is examined with algorithms based on dispersion relations for integer powers of complex reflection coefficient, which emerge as a powerful and yet uncommon tools in examining the consistency of the spectroscopic data. It is shown that these algorithms can be used in particular for checking the success of correction of the spectra by the methods of Vartiainen et al [1] and Lucarini et al [2] to remove the negative misplacement error in the terahertz time-domain spectroscopy.

cond-mat.mtrl-sci↗

arXiv2005

Dispersion relations of the powers of complex reflection coefficient in testing the validity of THz spectra

Kramers-Kronig type dispersion relations for integer powers of complex reflection coefficient are introduced for testing the consistency of terahertz reflection spectra. By using numerical simulations we show that such dispersion relations can be applied for distillation from data with some experimental artifacts without data extrapolations beyond the measured spectral range. These dispersion relations, due to causality, provide a powerful and yet uncommon tool to examine the consistency of the spectroscopic data obtained in reflection spectroscopy at terahertz range. In particular we show that real and imaginary parts of the complex reflection coefficient obtained from raw data with systematic phase error caused by sample misplacement, not necessarily obey dispersion relations, while the ones corrected with maximum entropy method obey these relations.

cond-mat.mtrl-sci↗

arXiv2005

Environmental Physics: Physical Principles and Applications

Environmental science almost invariably proposes problems of extreme complexity, typically characterized by strongly nonlinear evolution dynamics. The systems under investigation have many degrees of freedom - which makes them complicated - and feature nonlinear interactions of several different components taking place on a vast range of time-space scales - which makes them complex. Such systems evolve under the action of macroscopic driving (typically the solar heating) and modulating (e.g. the Earth's rotation and gravitation) agents. The most comprehensive example is the entire climatic system. The description of the macroscopic dynamics of environmental systems is based on the systematic use of dominant balances derived on a phenomenological basis in order to specialize the dynamical equations. Such balances are suitable classes of approximate solutions of the evolution equations which represent a reasonably good approximation to the actual observed fields when sufficiently large spatial or temporal averages are considered. Actually, different balances have to be considered depending on the time and space scales we are focusing our interest on. Such an approach reflects the fundamentally heuristic-inductive nature of the scientific research in environmental sciences, where the traditional reductionistic scientific attitude is not always effective. In order to exemplify this procedure, we consider the very relevant case of the motion of the fluids that permit the existence of life on the Earth, air and water: the so-called geophysical fluids.

physics.ao-ph↗

arXiv1998

General Properties of Optical Harmonic Generation from a simple Oscillator Model

The nonlinear oscillator model allows a basic understanding of all nonlinear processes and can be adopted to analyse optical vibrational modes and electronic transition in molecules and crystals, in order to derive general properties of harmonic generation to all orders. In particular, we obtain Kramers Kroenig relations and sum rules referred to all momenta of the susceptibility, and Miller's empirical rules to all orders. Since the above properties only depend on time causality and not on the specific microscopic model, they can be adopted for the quantum mechanical description, sustituting in the classical expression the derivatives of the potential with their expectation values.

physics.optics↗