Papers by Brunella Bonaccorso
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This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Analytical derivation of Severity-Area-Frequency curves for characterizing drought areal extent
EGU General Assembly Conference Abstracts, May 1, 2014
Drought is a natural phenomenon that exhibits spatial and temporal variability. The assessment of... more Drought is a natural phenomenon that exhibits spatial and temporal variability. The assessment of probabilities and/or return periods of areal extent of drought events of different severities over a region is of primary interest for an appropriate water resources management as well as for an effective drought preparedness and mitigation planning. In this study probabilistic characterization of the relationship between meteorological drought severity (computed in terms of Standardized Precipitation Index, SPI) and areal extent, expressed as Drought severity-Area- Probability (SAP) curves, is carried out through an analytical methodology. In particular, analytical expressions of SAP curves describing the proportion of the total area of the region of interest where the SPI values are below a fixed threshold are derived. The proposed methodology accounts for the spatial correlation of the SPI field, and the analytical form of the derived curves enables to draw general conclusions about ...
A Non Parametric Approach for Drought Forecasting Through the Standardized Precipitation Index
Due to a slow evolution in time, drought is a phenomenon whose consequences take a significant am... more Due to a slow evolution in time, drought is a phenomenon whose consequences take a significant amount of time with respect to its inception in order to be perceived by the socioeconomic systems. Due to this feature, an effective mitigation of drought impacts is possible, more than in the case of other extreme events (e.g. floods, earthquakes, hurricanes, etc.), provided a timely monitoring and/or forecasting of an incoming drought is available. Thus, an accurate selection of indices, able to provide drought forecast in addition to a synthetic and objective description of historical droughts, is essential to help decision makers to implement appropriate mitigation measures. The objective of this study is to contribute to the development of drought forecasting methodologies based on stochastic techniques, with particular reference to the Standardized Precipitation Index (SPI, McKee et al., 1993), which is one of the most widely applied index for drought monitoring. According to the pr...
Probabilistic characterization of drought properties through copulas
Physics and Chemistry of the Earth, Parts A/B/C, 2009
This paper shows an application of copulas to the probabilistic analysis of drought characteristi... more This paper shows an application of copulas to the probabilistic analysis of drought characteristics. Drought occurrences are analyzed by the Standardized Precipitation Index (SPI) computed on the mean areal precipitation, aggregated at 6months, observed in Sicily between 1921 and 2003. Assuming a drought period as a consecutive number of intervals where SPI values are less than− 1, several characteristics are determined, namely: drought length, mean and minimum SPI values, and drought mean areal extent. Results of a ...
Natural Hazards
Weather extremes have been responsible for widespread economic damage at global scale in the last... more Weather extremes have been responsible for widespread economic damage at global scale in the last decades. Agriculture alone absorbed 26% of the overall impact caused by natural hazards in low- and middle-income countries and even in high-income countries yield losses due to extreme weather are relevant. Vulnerability curves are traditionally used to quickly estimate the damage due to extreme events. This study maps the articles published from January 2000 to May 2022 implementing crop vulnerability curves to weather-related extreme events and climate change. Fifty-two articles have been identified through the use of Scopus, Web of Science, Google Scholar and the references of the selected papers. The selected papers have been analysed to determine for which extreme events vulnerability curves have been proposed, which crops have been studied, which explanatory variables have been used to create the curves, which functions are used to develop vulnerability curves and the number of p...
Hydrology, 2021
Groundwater is a major source of drinking water worldwide, often considered more reliable than su... more Groundwater is a major source of drinking water worldwide, often considered more reliable than surface water and more accessible. Nowadays, there is wide recognition by the scientific community that groundwater resources are under threat from overexploitation and pollution. Furthermore, frequent and prolonged drought periods due to climate change can seriously affect groundwater recharge. For an appropriate and sustainable management of water systems supplied by springs and/or groundwater withdrawn from aquifers through drilling wells or drainage galleries, the need arises to properly quantify groundwater resources availability, mainly at the monthly scale, as groundwater recharge is influenced by seasonality, especially in the Mediterranean areas. Such evaluation is particularly important for ungauged groundwater bodies. This is the case of the aquifer supplying the Santissima Aqueduct, the oldest water supply infrastructure of the city of Messina in Sicily (Southern Italy), whose ...
Advances in Geosciences, 2005
The objective of the study is to assess the presence of linear and non linear trends in annual ma... more The objective of the study is to assess the presence of linear and non linear trends in annual maximum rainfall series of different durations observed in Sicily. In particular, annual maximum rainfall series with at least 50 years of records starting from the 1920's are selected, and for each duration (1, 3, 6, 12 and 24 h) the Student's t test and the Mann-Kendall test, respectively, for linear and non linear trend detection, are applied also by means of bootstrap techniques. The effect of trend on the assessment of the return period of a critical event is also analysed. In particular, return periods related to a storm, recently occurred along the East Coast of Sicily, are computed by estimating parameters based on several sub-series extracted from the whole observation period. Such return period estimates are also compared with confidence intervals computed by bootstrap. Results indicate that for shorter durations, the investigated series generally exhibit increasing trends while as longer durations are considered, more and more series exhibit decreasing trends.
Natural Hazards and Earth System Sciences
Water Science and Technology Library, 2007
In dealing with drought, a proactive approach requires a drought monitoring, a drought forecastin... more In dealing with drought, a proactive approach requires a drought monitoring, a drought forecasting and an estimation of extreme dry event return times. For this purpose a useful tool is the drought bulletin where all the available information and analyses are collected and updated. In this chapter the main aspects of such approach are described and some sample applications for the Mediterranean area are shown. Results suggest that for a drought risk assessment there is not a unique analysis procedure; however, an ensemble of different kinds of analyses can provide useful information in preventing and minimizing the negative effects of drought events
Drought economic impacts, even if non-structural, are a significant threat for those sectors high... more Drought economic impacts, even if non-structural, are a significant threat for those sectors highly dependent on water resources. Agricultural production is highly sensitive to extreme weather events such as droughts and heatwaves. Climate change is expected to exacerbate the frequency and the severity of droughts, as stated by the Intergovernmental Panel on Climate Change (IPCC), which raises concerns about food security for the next decades.
The Standardized Precipitation Index (SPI) is a widely used index for drought monitoring purposes... more The Standardized Precipitation Index (SPI) is a widely used index for drought monitoring purposes that requires the preliminary fitting of a probability distribution to monthly precipitation aggregated at different time scales. The sampling properties of the SPI are investigated as a function of the sample size adopted for such distribution fitting. In particular, sampling properties of SPI, such as bias and mean square error (MSE), are analytically derived assuming the underlying precipitation series normally distributed, and compared with numerical values obtained by simulation for the cases of gamma and lognormal distributions. Also, the probabilities of correctly or incorrectly classifying drought conditions through the SPI are computed as a function of the available sample size. Results indicate that SPI values are significantly affected by the size of the sample adopted for its estimation. Furthermore, the theoretical MSE computed for the normal case fits well the one obtained...
Multivariate Probabilistic Characterization of Drought Events
In the present study a methodology for the analytical derivation of the multivariate cumulative p... more In the present study a methodology for the analytical derivation of the multivariate cumulative probability distribution (cdf) of drought characteristics based on the stochastic structure of the underlying water supply series and a threshold describing the water demand level is presented. The derived cdf’s are then applied to determine the return period of critical droughts by considering jointly two characteristics, e.g. droughts with accumulated deficit greater than a given value and fixed duration. By considering different combinations of drought characteristics, several types of critical droughts can be identified.
Investigating short and long-term effects of Natural and Human-Induced Shocks on a Water Resources System in Sicily (Italy) through Socio-Hydrological Modeling
A flow regime can be broadly categorised as perennial, intermittent or ephemeral, in 10 relation ... more A flow regime can be broadly categorised as perennial, intermittent or ephemeral, in 10 relation to the fact the stream flowing is continuous all year round or cheased for weeks or months 11 each year. Various conceptual models are needed to capture the behaviour of these different flow 12 regimes, which reflect the differences in stream-groundwater hydrologic connection. As the 13 hydrologic connection becomes more transient and a catchment’s runoff response more non-linear, 14 such as for intermittent streams, the need for explicit representation of the groundwater increases. 15 In the present study, we investigate the connection between Northern Etna groundwater system 16 and the Alcantara River Basin in Sicily, which is intermittent in the upstream and perennial since 17 the midstream due to groundwater resurgence. To this end, we apply a modified version of 18 IHACRES rainfall-runoff model, whose input data are continuous series of concurrent daily 19 streamflow, rainfall and t...
An Innovative Method for Flood Peak Event Separation from Discharge Time Series
A statistical framework for evaluating EURO-CORDEX simulations and derived drought characteristics
<p>Regional climate models (RCMs) are commonly used for assessing, at prope... more <p>Regional climate models (RCMs) are commonly used for assessing, at proper spatial resolutions, future impacts of climate change on hydrological events. In this study, we propose a statistical methodological framework to assess the quality of the EURO-CORDEX RCMs concerning their ability to simulate historic observed climate (temperature and precipitation). We specifically focus on the models’ performance in reproducing drought characteristics (duration, accumulated deficit, intensity, and return period) determined by the theory of runs at seasonal and annual timescales, by comparison with high-density and high-quality ground-based observational datasets. In particular, the proposed methodology is applied to the Sicily and Calabria regions (Southern Italy), where long historical precipitation and temperature series were recorded by the ground-based monitoring networks operated by the former Regional Hydrographic Offices. The density of the measurements is considerably greater than observational gridded datasets available at the European level, such as E-OBS or CRU-TS. Results show that among the models based on the combination of the HadGEM2 global circulation model (GCM) with the CLM-Community RCMs are the most skillful in reproducing precipitation and temperature variability as well as drought characteristics. Nevertheless, the ranking of the models may slightly change depending on the specific variable analysed, as well as the temporal and spatial scale of interest. From this point of view, the proposed methodology highlights the skills and weaknesses of the different configurations, aiding on the selection of the most suitable climate model for assessing climate change impacts on drought processes and the underlying variables.</p>
Statistical modeling of monthly rainfall variability in Soummam watershed of Algeria, between 1967 and 2018
Natural Resource Modeling
Regional sub-hourly extreme rainfall estimates in Sicily under a scale invariance framework
Water Resources Management
Design of urban drainage systems or flood risk assessment in small catchments often requires know... more Design of urban drainage systems or flood risk assessment in small catchments often requires knowledge of very short-duration rainfall events (less than 1 h). Unfortunately, data for these events are often unavailable or too scarce for a reliable statistical inference. However, regularities in the temporal pattern exhibited by storm records, known as scaling properties of rainfall, could help in characterizing extreme storms at partially gauged sites better than the application of traditional statistical techniques. In this work, a scaling approach for estimating the distribution of sub-hourly extreme rainfall in Sicily (Italy) is presented based on data from high-resolution rain gauges with a short functioning period and from low-resolution rain gauges with longer samples. First, simple scaling assumption was tested for annual maxima rainfall (AMR) data from 10 min to 24 h duration, revealing that the simple scaling regime holds from 20 to 60 min for most of the stations. Then, scaling homogeneous regions were classified based on the values of the scaling exponent. In each region, this parameter was regionalized through power-law relationships with the median of 1 h AMR data. After that, regional Depth Duration Frequency (DDF) curves were developed by combining the scale-invariant framework with the generalized extreme value (GEV) probability distribution and used to estimate T-year sub-hourly extreme rainfalls at sites where only rainfall data for longer durations (≥ 1 h) were available. The regional GEV simple scaling model was validated against sub-hourly historical observations at ten rain gauges, generally yielding, in relation to the scaling exponent value, to similar or better sub-hourly estimates than empirical approach.
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Papers by Brunella Bonaccorso