1,721,072 research outputs found
Modelli afflussi-deflussi per il preannuncio delle piene in tempo reale e ruolo dei principali processi fisici sulla loro efficacia
No full textDopo una sintetica descrizione della struttura dei modelli di preannuncio delle piene in tempo reale, viene brevemente discussa una analisi comparativa di vari modelli operativi, largamente usati, effettuata dalla World Meteorological Organization. I modelli in questione sono continui ed in configurazione sia a parametri concentrati sia distribuiti. Viene poi descritto un modello per il preannuncio delle piene in tempo reale su bacini di medie e grandi dimensioni. Il modello, applicabile ad eventi isolati e di tipo concettuale semi-distribuito, in aggiunta alle piogge utilizza come dati di ingresso le portate misurate in sezioni a monte. Sono evidenziate le accuratezze dei modelli e sono individuate le componenti le cui rappresentazioni devono essere migliorate. Infine utilizzando un modello di simulazione piogge-portate viene illustrata, per un piccolo bacino idrografico (135 Km2), la sensibilità delle portate di piena a variazioni di distribuzione della pioggia nello spazio e nel tempo
Representation of infiltration in adaptive rainfall-runoff models
No full textThe reliability of the extended Time Compression Approximation (TCA), commonly adopted in watershed models in order to represent the infiltration associated with erratic rainfalls, is investigated. This approximation is considered as a component of an adaptive real-time flood forecasting model. The forecasted flows are compared with those obtained replacing the extended TCA with the Complex Storm point Infiltration Model (CSPIM) recently proposed by Smith et al. (1993). The discharge forecasted through the infiltration component based on the numerical solution of Richards’ equation is used as a bench mark. The models were applied to situations representative of real areas in central Italy. The CSPIM based watershed model was found to provide excellent results. The TCA based model, in spite of the adaptive component, yielded poor results for various rainfall patterns. However, it seems to be a reasonable approximation when a uniform rainfall spatial distribution is involved
Tannins characterization by 31P-NMR
No full textTannins are secondary metabolites of plants employed as insect and parasite repellent to prevent plague tissues. This peculiarity is related to the inhibition of extracellular enzymes that occurs through the complexation of peptides by means of several cross linking hydrogen bond with their many phenolic functions. The characteristics of these interactions are not completely clear, as the structure of these heterogeneous polyphenols molecules. We developed a new analytical method for the structural characterization of tannins based on the 31P-NMR technique that allows both the quantitative and the qualitative characterisation of all labile OH groups present in tannins
Parametrizzazione dell’infiltrazione nella modellistica di preannuncio delle piene in tempo reale
No full textViene discusso un approccio per la rappresentazione del processo di infiltrazione nell'ambito di una modellistica concettuale semplificata per il preannuncio delle piene in tempo reale. L'approccio si basa sulla estensione di una formulazione puntuale a due parametri realizzata considerando la variabilità spaziale dell'infiltrazione e descrivendo la sua evoluzione temporale in termini di una successione di fasi. Ciascuna fase è composta di due stadi identificati attraverso il tempo di raggiungimento della saturazione alla superficie del suolo. La validità di tale formulazione è stata investigata attraverso applicazioni del modello di preannuncio delle piene su eventi reali con idrogrammi determinati da periodi di pioggia ben distinti
Modeling of rainfall infiltration in complex storm through modified rectangular profiles
No full textThe original model proposed by [1] and W is formulated here in a more homogeneous version which is easier for applications A series of infiltration-redistribution cycles is represented on a continuous basis utilizing only a basic equation for the evolution in time of surface water content. This equation was derived through averaged forms of the mass balance equation and Darcy’s law applied for a distorted shape of the soil moisture profile whose area is a fixed fraction of a rectangle. It is used to simulate ‘actual’ profiles which are represented by a single distorted profile or, at most, by combining two of them according to the behaviour of soil moisture flux with time. A merging condition for compound profiles is also adopted. The model effectiveness was examined by comparison with numerical solutions of Richards’ equation performed using a variety of synthetic experiments with stepwise uniform flux on a fine-textured soil. The
model was found to be suitable with accuracy comparable to that of the original version in spite of its reduced complexity
Modellistica dell’infiltrazione per eventi di pioggia discontinui
No full textViene presentato un modello per suoli a tessitura fine descrivente, su base temporale continua, il processo infiltrazione-redistribuzione-reinfiltrazione associato a complessi eventi di pioggia. Esso consiste in una forma semplificata di un modello (CSPIM) recentemente proposto da Smith et al. (1992) ottenuto attraverso una riduzione del numero di parametri incorporati. Il modello è stato verificato mediante confronto con il CSPIM e indirettamente con la soluzione numerica dell'equazione di Richards. I risultati ottenuti hanno evidenziato una adeguata affidabilità del modello, particolarmente per il suo inserimento come componente di un modello di preannuncio delle piene in tempo reale
Basin geomorphology-river response through the Horton-Strahler ordering scheme
No full textAn analysis was performed of the usefulness of representing basin response to rainfall by averaging the channel network geometry on the basis of the Horton/Strahler ordering scheme. Such an approach was applied to actual and synthetic events over large Italian basins and its results compared with those obtained by classical methods. It is pointed out that this approach is unsuitable if the spatial variability of effective rainfall is incorporated. However, its use seems to be practical and appropriate in describing basin response in terms of a unit hydrograph, particularly for ungauged basins
Elaborazione di afflussi e deflussi in tempo reale mediante modelli stocastico deterministici
No full textSpatial distribution of pre-warm front rainfall in the Mediterranean Area
No full textEvidence is given of the distribution of pre-warm front rainfall at the meso-g scale, together with a discussion of the main mechanisms producting this variability. An inland region in the Mediterranean area is considered. The selected rainfall type is commonly considered the most regular inasmuch as it is usually unaffected by extended convective motions. Despite this, within a storm a large variability in space was observed. For 90% of measurements, the typical deviations from the area-average total depth ranged from -40 to 60% and the storm ensemble-average rainfall rate over an hilly zone was 60% greater than that in a contiguous low-land zone generally placed upwind. This variability is largely explained in terms of forced uplift of air mass over an envelope type orography. For a few storms smaller orographic effects were found in locations influenced by an orography with higher slopes and elevations. This feature is ascribed to the compact structure of these mountains which probably determines a deflection of air mass in the boundary layer. The importance of this type of analysis in the hydrological practice is also emphasized
- …
