Assessing the impact of seasonal-rainfall anomalies on catchment-scale water balance components

Abstract. Although water balance components at the catchment scale are strongly related to annual rainfall, the availability of water resources in Mediterranean catchments also depends on rainfall seasonality. Observed seasonal anomalies in historical records are fairly episodic, but an increase in their frequency might exacerbate water deficit or water excess if the rainy season shortens or extends its duration, e.g., due to climate change. This study evaluates the sensitivity of water yield, evapotranspiration, and groundwater recharge to changes in rainfall seasonality by using the Soil Water Assessment Tool (SWAT) model applied to the upper Alento River catchment (UARC) in southern Italy, where a long time series of daily rainfall is available from 1920 to 2018. We compare two distinct approaches: (i) a "static" approach, where three seasonal features (namely rainy, dry, and transition fixed-duration 4-month seasons) are identified through the standardized precipitation index (SPI) and (ii) a "dynamic" approach based on a stochastic framework, where the duration of two seasons (rainy and dry seasons) varies from year to year according to a probability distribution. Seasonal anomalies occur when the transition season is replaced by the rainy or dry season in the first approach and when season duration occurs in the tails of its normal distribution in the second approach. Results are presented within a probabilistic framework. We also show that the Budyko curve is sensitive to the rainfall seasonality regime in UARC by questioning the implicit assumption of a temporal steady state between annual average dryness and the evaporative index. Although the duration of the rainy season does not exert a major control on water balance, we were able to identify season-dependent regression equations linking water yield to the dryness index in the rainy season

The Role of Volunteered Geographic Information towards 3D Property Cadastral Systems (2): A Purpose Driven Web Application

VGI has not proved to be readily suitable to replace well-established accurate methods and technologies such as those of full standard cadastral surveys. Even so, VGI potentialities as relevant source of geospatial data have been widely acknowledged. As such, some authors have defended that VGI may in fact play an important role such as at a local cadastral jurisdiction level towards local spatial data infrastructures. As far as property cadastre is concerned, the full extent 3D complexity inside a property is in many instances only known to their occupants, thus making crowd sourcing perhaps the only economically feasible approach for its capture. While the crowd cannot be expected to conduct a full cadastral survey, it may be possible to ask them to indicate at least the location of complex 3D situations and thus to facilitate local authorities’ understanding of the extent of some cadastral issues. As such, it was argued in our previous work that geoinformation from the crowd might in fact be taken into account as an interim step before a full surveyed 3D cadastre is eventually achieved. As such, possible room for VGI in the context of 3D cadastre was discussed, and a hierarchical framework of levels of data acquisition to be used at local cadastral jurisdiction level was proposed. Such framework is revisited in this paper.Given context above, this paper focuses primarily on two aspects. Firstly, to review technical requirements of the official cadastral process in Portugal in order to identify which sorts of cadastral data are likely to be acquirable/not acquirable through VGI. Secondly, to design and to implement the prototype of a web-based application (IGV3Dcad) envisaged for general public usage to flag different land and property ownership situations. Having information about the extent of the 2D/3D issue is also fundamental to making a decision as to whether a 3D cadastral approach is actually needed and hence to further invest resources in even more expensive 3D survey

XMM-Newton and Swift observations of XTE J1743-363

XTEJ1743-363 is a poorly known hard X-ray transient, that displays short and intense flares similar to those observed from Supergiant Fast X-ray Transients. The probable optical counterpart shows spectral properties similar to those of an M8 III giant, thus suggesting that XTEJ1743-363 belongs to the class of the Symbiotic X-ray Binaries. In this paper we report on the first dedicated monitoring campaign of the source in the soft X-ray range with XMM-Newton and Swift/XRT. T hese observations confirmed the association of XTEJ1743-363 with the previously suggested M8 III giant and the classification of the source as a member of the Symbiotic X-ray binaries. In the soft X-ray domain, XTEJ1743-363 displays a high absorption (~6x10^22 cm^-2 ) and variability on time scales of hundreds to few thousand seconds, typical of wind accreting systems. A relatively faint flare (peak X-ray flux 3x10^-11 erg/cm^2/s) lasting ~4 ks is recorded during the XMM-Newton observation and interpreted in terms of the wind accretion scenario.Comment: Accepted for publication on A&

Relaxation to equilibrium driven via indirect control in Markovian dynamics

We characterize to what extent it is possible to modify the stationary states of a quantum dynamical semigroup, that describes the irreversible evolution of a two-level system, by means of an auxiliary two-level system. We consider systems that can be initially entangled or uncorrelated. We find that the indirect control of the stationary states is possible, even if there are not initial correlations, under suitable conditions on the dynamical parameters characterizing the evolution of the joint system.Comment: revtex4, 7 page

Numerical solution of the radiative transfer equation: X-ray spectral formation from cylindrical accretion onto a magnetized neutron star

Predicting the emerging X-ray spectra in several astrophysical objects is of great importance, in particular when the observational data are compared with theoretical models. To this aim, we have developed an algorithm solving the radiative transfer equation in the Fokker-Planck approximation when both thermal and bulk Comptonization take place. The algorithm is essentially a relaxation method, where stable solutions are obtained when the system has reached its steady-state equilibrium. We obtained the solution of the radiative transfer equation in the two-dimensional domain defined by the photon energy E and optical depth of the system tau using finite-differences for the partial derivatives, and imposing specific boundary conditions for the solutions. We treated the case of cylindrical accretion onto a magnetized neutron star. We considered a blackbody seed spectrum of photons with exponential distribution across the accretion column and for an accretion where the velocity reaches its maximum at the stellar surface and at the top of the accretion column, respectively. In both cases higher values of the electron temperature and of the optical depth tau produce flatter and harder spectra. Other parameters contributing to the spectral formation are the steepness of the vertical velocity profile, the albedo at the star surface, and the radius of the accretion column. The latter parameter modifies the emerging spectra in a specular way for the two assumed accretion profiles. The algorithm has been implemented in the XSPEC package for X-ray spectral fitting and is specifically dedicated to the physical framework of accretion at the polar cap of a neutron star with a high magnetic field (> 10^{12} G), which is expected to be typical of accreting systems such as X-ray pulsars and supergiant fast X-ray transients.Comment: 13 pages, 20 figures, accepted for publication in A&

Multi-wavelength observations of IGR J17544-2619 from quiescence to outburst

In this paper we report on a long multi-wavelength observational campaign of the supergiant fast X-ray transient prototype IGR J17544-2619. A 150 ks-long observation was carried out simultaneously with XMM-Newton and NuSTAR, catching the source in an initial faint X-ray state and then undergoing a bright X-ray outburst lasting about 7 ks. We studied the spectral variability during outburst and quiescence by using a thermal and bulk Comptonization model that is typically adopted to describe the X-ray spectral energy distribution of young pulsars in high mass X-ray binaries. Although the statistics of the collected X-ray data were relatively high we could neither confirm the presence of a cyclotron line in the broad-band spectrum of the source (0.5-40 keV), nor detect any of the previously reported tentative detection of the source spin period. The monitoring carried out with Swift/XRT during the same orbit of the system observed by XMM-Newton and NuSTAR revealed that the source remained in a low emission state for most of the time, in agreement with the known property of all supergiant fast X-ray transients being significantly sub-luminous compared to other supergiant X-ray binaries. Optical and infrared observations were carried out for a total of a few thousands of seconds during the quiescence state of the source detected by XMM-Newton and NuSTAR. The measured optical and infrared magnitudes were slightly lower than previous values reported in the literature, but compatible with the known micro-variability of supergiant stars. UV observations obtained with the UVOT telescope on-board Swift did not reveal significant changes in the magnitude of the source in this energy domain compared to previously reported values.Comment: Accepted for publication on A&A. V2: few typos correcte

Spin relaxation rates in quasi-one-dimensional coupled quantum dots

We study theoretically the spin relaxation rate in quasi-one-dimensional coupled double semiconductor quantum dots. We consider InSb and GaAs-based systems in the presence of the Rashba spin-orbit interaction, which causes mixing of opposite-spin states, and allows phonon-mediated transitions between energy eigenstates. Contributions from all phonon modes and coupling mechanisms in zincblende semiconductors are taken into account. The spin relaxation rate is shown to display a sharp, cusp-like maximum as function of the interdot-barrier width, at a value of the width which can be controlled by an external magnetic field. This remarkable behavior is associated with the symmetric-antisymmetric level splitting in the structure.Comment: 4 figures, Submitted to Applied Physics Letter

Embedding initial data for black hole collisions

We discuss isometric embedding diagrams for the visualization of initial data for the problem of the head-on collision of two black holes. The problem of constructing the embedding diagrams is explicitly presented for the best studied initial data, the Misner geometry. We present a partial solution of the embedding diagrams and discuss issues related to completing the solution.Comment: (27pp text, 11 figures

Impact of positivity and complete positivity on accessibility of Markovian dynamics

We consider a two-dimensional quantum control system evolving under an entropy-increasing irreversible dynamics in the semigroup form. Considering a phenomenological approach to the dynamics, we show that the accessibility property of the system depends on whether its evolution is assumed to be positive or completely positive. In particular, we characterize the family of maps having different accessibility and show the impact of that property on observable quantities by means of a simple physical model.Comment: 11 pages, to appear in J. Phys.