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4. Rainfall data augmentation in Northern Italy through daily extremes and the Hershfield factor.

Author

Mazzoglio, Paola, Butera, Ilaria, and Claps, Pierluigi

Subjects
DATA augmentation, RAINFALL measurement, RAIN gauges, RAINFALL, WATERSHEDS
Abstract

The majority of rainfall measurements in the world is at the daily scale, i.e. related to a specific calendar day and measured over fixed 24 h. On these data, daily annual maximum rainfall depths (F -maxima) series are easily obtained. On the other hand, 24 h annual maximum rainfall depths (S -maxima), which refer to a period starting at any instant, are more useful indicators. S -maxima values cannot be less than the F -maxima, and are generally higher. The ratio between these extremes, called Hershfield factor (H), has been studied to move from F -maxima to S -maxima, allowing to take advantage of the relevant amount of information included in historical records of daily extremes. For instance, before 1980, in the Italian Hydrological Yearbooks only a subset (< 50 %) of the rain gauges was equipped with a recording device, from which annual maxima over 1, 3, 6, 12 and 24 consecutive hours can be derived. In this study we investigate the possibility of using F -maxima to complement the S -maxima records related to the Po river basin and the Liguria region (North of Italy). As a first step we retrieved from official databases all the daily rainfall measurements, available over this area, from early 1900 until today and we quality-controlled the measurements. We then computed the annual H for all the stations and all the years where both the F - and S -maxima were available, to obtain data that can be analyzed in their temporal and spatial variability. The spatial distribution of the Hershfield factor shows values similar to the ones suggested in the literature and is related to the geographic position of the stations, allowing the possibility to identify some distinct areas with positive or negative anomalies. The obtained map of the H factor, with interpolated local anomalies, allows to reconstruct the missing S -maxima in stations with only F -maxima, and improve the knowledge of the spatial variability of sub-daily rainfall extremes. [ABSTRACT FROM AUTHOR]

Published
2024
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8. Investigating orographic gradients and rainfall extremes through local regression models: an application over Italy

Author

Mazzoglio, Paola, Butera, Ilaria, and Claps, Pierluigi

Abstract

In areas with complex morphology the spatial variability of rainfall depths is known to be affected by the elevation, with orographic gradients that can vary depending on the duration and the location. In this work, more than 3800 time series of sub-daily annual maximum rainfall depths with at least 10 years of data are used to estimate the spatial variability of the average rainfall extremes over Italy. Most of the variability depends on elevation and this dependence is considered through a local regression approach applied to all the cells available in a grid with resolution of 1 km. The model is developed by considering various aspects, such as the low data density of some areas, the minimum difference in elevation of the sample, and the difficulties in extrapolating to high and low elevations.This model allows us to reconstruct maps of average extremes that consider the local effects of the topography. Our results indicate that, for the 1 h extremes, a negative gradient is present in large mountainous areas. In contrast, the 24 h mean rainfall extremes usually have positive orographic gradients, except for a few mountainous regions. In most cases, our findings confirm previous investigations available over areas of limited extension. The proposed approach allows us to identify areas where the reverse orographic effect occurs, providing a basis for future research on the underlying physical mechanisms. In addition, the obtained maps can be used in studies that focus on the spatial variability of rainfall quantiles, needed for hydrological design., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

Published
2023

30. The role of morphology on the spatial distribution of short-duration rainfall extremes in Italy.

Author

Mazzoglio, Paola, Butera, Ilaria, Alvioli, Massimiliano, and Claps, Pierluigi

Abstract

The dependence of rainfall on elevation has frequently been documented in the scientific literature and may be relevant in Italy, due to the high degree of geographical and morphological heterogeneity of the country. However, a detailed analysis of the spatial variability of short-duration rainfall extremes and their connection to the landforms does not exist. Using a new, comprehensive and position-corrected rainfall extreme dataset (I²-RED), we present a systematic study of the relationship between geomorphological forms and the average of rainfall extremes (index rainfall) across the whole of Italy. We first investigated the dependence of sub-daily rainfall depths on elevation and other landscape indices through univariate and multivariate linear regressions. After analyzing the results, we repeated the analysis on geomorphological subdivisions of Italy. The results of the national-scale regression analysis did not confirm the assumption of elevation being the sole driver of the variability of rainfall extremes. The longitude, latitude, distance from the coastline, morphological obstructions and mean annual rainfall resulted to be significantly related to the index rainfall, and to play different roles for different durations (1- to 24-hours). However, when comparing the results of the best multivariate regression models with univariate regressions for morphological subdivisions, we found that "local" rainfall-topography relationships within the geomorphological subdivisions outperformed the country-wide multiple regressions and offered a reasonable representation of the effect of morphology on rainfall extremes. [ABSTRACT FROM AUTHOR]

Published
2021
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37. Impianti mini hydro nei condotti fognari

Author

Balestra, R., Butera, Ilaria, Isola, R., Lombardi, M., and Spina, N.

Subjects
recupero energetico, Mini-micro hydro, sistemi fognari, ruote idrauliche, Mini-micro hydro, recupero energetico, ruote idrauliche, sistemi fognari
Published
2016

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