A space-time generator for rainfall nowcasting: the PRAISEST model

International audienceThe paper introduces a new stochastic technique for forecasting rainfall in space-time domain: the PRAISEST Model (Prediction of Rainfall Amount Inside Storm Events: Space and Time). The model is based on the assumption that the rainfall height H accumulated on an interval ?t between the instants i?t and (i+1)?t and on a spatial cell of size ?x?y is correlated either with a variable Z, representing antecedent precipitation at the same point, either with a variable W, representing simultaneous rainfall at neighbour cells. The mathematical background is given by a joined probability density fH,W,Z (h,w,z) in which the variables have a mixed nature, that is a finite probability for null value and infinitesimal probabilities for the positive values. As study area, the Calabria region, in Southern Italy, has been selected. The region has been discretised by 10 km×10 km cell grid, according to the raingauge network density in this area. Storm events belonging to 1990?2004 period were analyzed to test performances of the PRAISEST model

Occurrence analysis of daily rainfalls through non-homogeneous Poissonian processes

Abstract. A stochastic model based on a non-homogeneous Poisson process, characterised by a time-dependent intensity of rainfall occurrence, is employed to explain seasonal effects of daily rainfalls exceeding prefixed threshold values. The data modelling has been performed with a partition of observed daily rainfall data into a calibration period for parameter estimation and a validation period for checking on occurrence process changes. The model has been applied to a set of rain gauges located in different geographical areas of Southern Italy. The results show a good fit for time-varying intensity of rainfall occurrence process by 2-harmonic Fourier law and no statistically significant evidence of changes in the validation period for different threshold values

Rainfall nowcasting by at site stochastic model P.R.A.I.S.E.

The paper introduces a stochastic model to forecast rainfall heights at site: the P.R.A.I.S.E. model (Prediction of Rainfall Amount Inside Storm Events). PRAISE is based on the assumption that the rainfall height <I>H_i</I>+1 accumulated on an interval &Delta;<I>t</I> between the instants <I>i&Delta;t</I> and <I>(i+1&Delta;t</I> is correlated with a variable <I>Z_i^(&nu;)</I>, representing antecedent precipitation. The mathematical background is given by a joined probability density <I>f_{H_i+1}, Z_i^(&nu;)(h_i+1 ,z_i^(&nu;)</I>) in which the variables have a mixed nature, that is a finite probability in correspondence to the null value and infinitesimal probabilities in correspondence to the positive values. As study area, the Calabria region, in Southern Italy, was selected, to test performances of the PRAISE model

Heparin Induces Harmless Fibril Formation in Amyloidogenic W7FW14F Apomyoglobin and Amyloid Aggregation in Wild-Type Protein In Vitro

Glycosaminoglycans (GAGs) are frequently associated with amyloid deposits in most amyloid diseases, and there is evidence to support their active role in amyloid fibril formation. The purpose of this study was to obtain structural insight into GAG-protein interactions and to better elucidate the molecular mechanism underlying the effect of GAGs on the amyloid aggregation process and on the related cytotoxicity. To this aim, using Fourier transform infrared and circular diochroism spectroscopy, electron microscopy and thioflavin fluorescence dye we examined the effect of heparin and other GAGs on the fibrillogenesis and cytotoxicity of aggregates formed by the amyloidogenic W7FW14 apomyoglobin mutant. Although this protein is unrelated to human disease, it is a suitable model for in vitro studies because it forms amyloid-like fibrils under physiological conditions of pH and temperature. Heparin strongly stimulated aggregation into amyloid fibrils, thereby abolishing the lag-phase normally detected following the kinetics of the process, and increasing the yield of fibrils. Moreover, the protein aggregates were harmless when assayed for cytotoxicity in vitro. Neutral or positive compounds did not affect the aggregation rate, and the early aggregates were highly cytotoxic. The surprising result that heparin induced amyloid fibril formation in wild-type apomyoglobin and in the partially folded intermediate state of the mutant, i.e., proteins that normally do not show any tendency to aggregate, suggested that the interaction of heparin with apomyoglobin is highly specific because of the presence, in protein turn regions, of consensus sequences consisting of alternating basic and non-basic residues that are capable of binding heparin molecules. Our data suggest that GAGs play a dual role in amyloidosis, namely, they promote beneficial fibril formation, but they also function as pathological chaperones by inducing amyloid aggregation

A Laboratory Study on the Use of Optical Fibers for Early Detection of Pre-Failure Slope Movements in Shallow Granular Soil Deposits

Although landsliding is the macroscopic effect of slope failure, it is only the final stage of an often time-consuming process of soil deformation. In many cases, slope movement remains extremely slow and undetected for a long time; in other cases, failure is abrupt, preceded by small deformations and followed by rapid, destructive movements. This is the case of slope failure in granular soils of pyroclastic nature, which involve an extensive mountainous area surrounding Mt. Vesuvius in southern Italy. Given that the area around Vesuvius is highly urbanized and densely populated, the detection and interpretation of pre-failure slope deformations are of great importance for risk mitigation. To this aim, Brillouin optical time-domain analysis (BOTDA), a distributed fiber optic sensing technique, may represent an efficient new tool. This paper illustrated the results of laboratory experiments on small-scale slopes instrumented with optical fiber sensors, showing the main features of this technique for early detection of slope failure