Papers by Rui A P Perdigao
A warming climate is expected to have an impact on the magnitude and timing of river floods; howe... more A warming climate is expected to have an impact on the magnitude and timing of river floods; however, no consistent large-scale climate change signal in observed flood magnitudes has been identified so far. We analyzed the timing of river floods in Europe over the past five decades, using a pan-European database from 4262 observational hydrometric stations, and found clear patterns of change in flood timing. Warmer temperatures have led to earlier spring snowmelt floods throughout northeastern Europe; delayed winter storms associated with polar warming have led to later winter floods around the North Sea and some sectors of the Mediterranean coast; and earlier soil moisture maxima have led to earlier winter floods in western Europe. Our results highlight the existence of a clear climate signal in flood observations at the continental scale.
![Research paper thumbnail of A two-dimensional numerical scheme of dry/wet fronts for the Saint-Venant system of shallow water equations [by Zsolt Horváth, Jürgen Waser, Rui A. P. Perdigão, Artem Konev, Günter Blöschl]](https://a.academia-assets.com/images/blank-paper.jpg)
A two-dimensional numerical scheme of dry/wet fronts for the Saint-Venant system of shallow water equations [by Zsolt Horváth, Jürgen Waser, Rui A. P. Perdigão, Artem Konev, Günter Blöschl]
We propose a new two-dimensional numerical scheme to solve the Saint-Venant system of shallow wat... more We propose a new two-dimensional numerical scheme to solve the Saint-Venant system of shallow water equations in the presence of partially flooded cells. Our method is well balanced, positivity preserving, and handles dry states. The latter is ensured by using the draining time step technique in the time integration process, which guarantees non-negative water depths. Unlike previous schemes, our technique does not generate high velocities at the dry/wet boundaries, which are responsible for small time step sizes and slow simulation runs. We prove that the new scheme preserves ‘lake at rest’ steady states and guarantees the positivity of the computed fluid depth in the partially flooded cells. We test the new scheme, along with another recent scheme from the literature, against the analytical solution for a parabolic basin and show the improved simulation performance of the new scheme for two real-world scenarios. Copyright © 2014 John Wiley & Sons, Ltd.
Non-Gaussian multivariate probability distributions, derived from climate and geofluid statistics... more Non-Gaussian multivariate probability distributions, derived from climate and geofluid statistics, allow for nonlinear correlations between linearly uncorrelated components, due to joint Shannon negentropies. Triadic statistical dependence under pair-wise (total or partial) independence is thus possible. Synergy or interaction information among triads is estimated. We formulate an optimization method of triads in the space of orthogonal rotations of normalized principal components, relying on the maximization of thirdorder cross-cumulants. Its application to a minimal onedimensional, periodic, advective model leads to enhanced triads that occur between oscillating components of circular or locally confined wave trains satisfying the triadic wave resonance condition.
This study investigates the sensitivity of floods to annual precipitation in space and time and e... more This study investigates the sensitivity of floods to annual precipitation in space and time and evaluates quantitative signs of landscape-climate coevolution. For that purpose, a spatiotemporal sensitivity analysis is performed at regional scale using data from 804 catchments in Austria from 1976 to 2008. Results show that flood peaks are more responsive to spatial (regional) than to temporal (decadal) variability. Space-wise a 10% increase in precipitation leads to a 23% increase in flood peaks in Austria, whereas time- wise a 10% increase in precipitation leads to an increase of just 6% in flood peaks. Catchments from dry lowlands and high wetlands exhibit similarity between the spatial and temporal sensitivities (spatiotemporal symmetry) and low landscape-climate codependence. This suggests that such regions are not coevolving significantly. However, intermediate regions show differences between those sensitivities (symmetry breaks) and higher landscape-climate codependence, suggesting undergoing coevolution. A new coevolution index is then proposed relating spatiotemporal symmetry with relative characteristic celerities. The descriptive assessment of coevolution is complemented by a simple dynamical model of landscape-climate coevolu- tion, in which landform evolution processes take place at the millennial scale (slow dynamics), and climate adjusts in years to decades (fast dynamics). Coevolution is expressed by the interplay between slow and fast dynamics, represented, respectively, by spatial and temporal characteristics. The model captures key features of the joint landscape-climate distribution, supporting the descriptive assessment. This paper ulti- mately brings to light that coevolution needs to be taken into account through characteristic celerities in space-time trading of regional hydrology.
Minimum Mutual Information and Non-Gaussianity through the Maximum Entropy Method: Estimation from Finite Samples
Minimum Mutual Information and Non-Gaussianity Through the Maximum Entropy Method: Theory and Properties
Kepler Shuffle for Real-World Flood Simulations on GPUs. [by Zsolt Horvath, Rui AP Perdigao, Juergen Waser, Daniel Cornel, Artem Konev, and Guenter Bloeschl]
We present a new graphics processing unit implementation of two second-order numerical schemes of... more We present a new graphics processing unit implementation of two second-order numerical schemes of the shallow water equations on Cartesian grids. Previous implementations are not fast enough to evaluate multiple scenarios for a robust, uncertainty-aware decision support. To tackle this, we exploit the capabilities of the NVIDIA Kepler architecture. We implement a scheme developed by Kurganov and Petrova (KP07) and a newer, improved version by Horva ́th et al. (HWP14). The KP07 scheme is simpler but suffers from incorrect high velocities along the wet/dry boundaries, resulting in small time steps and long simulation runtimes. The HWP14 scheme resolves this problem but comprises a more com- plex algorithm. Previous work has shown that HWP14 has the potential to outperform KP07, but no practical imple- mentation has been provided. The novel shuffle-based implementation of HWP14 presented here takes advantage of its accuracy and performance capabilities for real-world usage. The correctness and performance are validated on real- world scenarios.
The current work addresses one of the key building blocks towards an improved understanding of fl... more The current work addresses one of the key building blocks towards an improved understanding of flood processes and associated changes in flood characteristics and regimes in Europe: the development of a comprehensive, extensive European flood database. The presented work results from ongoing cross-border research collaborations initiated with data collection and joint interpretation in mind. A detailed account of the current state, characteristics and spatial and temporal coverage of the European Flood Database, is presented.
There is growing concern that flooding is becoming more frequent and severe in Europe. A better u... more There is growing concern that flooding is becoming more frequent and severe in Europe. A better understanding of flood regime changes and their drivers is therefore needed. The paper reviews the current knowledge on flood regime changes in European rivers that has traditionally been obtained through two alternative research approaches. The first approach is the data-based detection of changes in observed flood events. Current methods are reviewed together with their challenges and opportunities. For example, observation biases, the merging of different data sources and accounting for nonlinear drivers and responses. The second approach consists of modelled scenarios of future floods. Challenges and opportunities associated with flood change scenarios are discussed such as fully accounting for uncertainties in the modelling cascade and feedbacks. To make progress in flood change research, we suggest that a synthesis of these two approaches is needed. This can be achieved by focusing on long duration records and flood-rich and floodpoor periods rather than on short duration flood trends only, by formally attributing causes of observed flood changes, by validating scenarios against observed flood regime dynamics, and by developing low-dimensional models of flood changes and feedbacks. The paper finishes with a call for a joint European flood change research network.
Österreichische Ingenieur-und Architekten-Zeitschrift, 160. Jg., Heft 1-12/2015 1 management meas... more Österreichische Ingenieur-und Architekten-Zeitschrift, 160. Jg., Heft 1-12/2015 1 management measures. Appropriate methods are needed to assist in the implementation of these measures. This paper reviews new methodological developments on the following themes: hazard mapping, large scale interactions of floods, residual risk (flood prevention); retaining water in the landscape, linear protection measures, flood retention (flood mitigation); public participation, outreach and education (awareness); flood warning, emergency plans (preparation); assessment of flood damage, event documentation (recovery). The new methods are intended to contribute to even more reliable and more efficient management of flood risks.
Land surface temperature from multiple geostationary satellites [by Sandra C. Freitas , Isabel F. Trigo , João Macedo , Carla Barroso , Ricardo Silva & Rui Perdigão]
This article provides a description of a land surface temperature (LST) data set generated (and p... more This article provides a description of a land surface temperature (LST) data set generated (and provided in near-real-time or offline) based on infrared data from sensors onboard different geostationary (GEO) satellites: Meteosat Second Generation (MSG), Geostationary Operational Environmental Satellite (GOES), and Multifunction Transport Satellite (MTSAT). Given the different characteristics of the imagers onboard each GEO platform, different algorithmic methodologies for the retrieval of LST are presented and implemented – namely the Generalized Split-Window (GSW) algorithm and the Dual Algorithm (DA) in its mono- and dual-channel forms – using semi-empirical functions that relate LST to top-of-atmosphere brightness temperatures in infrared window channels. The assumptions and physics underlying each methodology, as well as the uncertainties of LST estimates, are discussed. The formulations are trained using a data set of radiative transfer simulations for a wide range of atmospheric and surface conditions. The performance of each algorithm is then assessed by comparing its output against an independent set of simulations, suggesting that product uncertainties range from 2°C (for GSW and the two-channel algorithm) to 4°C (for the one-channel algorithm). Finally, LST retrievals from different GEO satellites are merged into a single field. In overlapping areas, the average discrepancies between LST products derived from GOES and from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) onboard MSG are within 1°C during night-time, but may reach 3°C during daytime. Over those areas, the merged LST field is obtained as a weighted average of available LST retrievals for the same time slot, taking into account the respective error bar.
Hydrology and Earth System Sciences, 2014
There is growing concern that flooding is becoming more frequent and severe in Europe. A better u... more There is growing concern that flooding is becoming more frequent and severe in Europe. A better understanding of flood regime changes and their drivers is therefore needed. The paper reviews the current knowledge on flood regime changes in European rivers that has traditionally been obtained through two alternative research approaches. The first approach is the data-based detection of changes in observed flood events. Current methods are reviewed together with their challenges and opportunities. For example, observation biases, the merging of different data sources and accounting for nonlinear drivers and responses. The second approach consists of modelled scenarios of future floods. Challenges and opportunities associated with flood change scenarios are discussed such as fully accounting for uncertainties in the modelling cascade and feedbacks. To make progress in flood change research, we suggest that a synthesis of these two approaches is needed. This can be achieved by focusing on long duration records and flood-rich and floodpoor periods rather than on short duration flood trends only, by formally attributing causes of observed flood changes, by validating scenarios against observed flood regime dynamics, and by developing low-dimensional models of flood changes and feedbacks. The paper finishes with a call for a joint European flood change research network.
Proceedings of the International Association of Hydrological Sciences, Jun 11, 2015
The current work addresses one of the key building blocks towards an improved understanding of flo... more The current work addresses one of the key building blocks towards an improved understanding of flood processes and associated changes in flood characteristics and regimes in Europe: the development of a comprehensive, extensive European flood database. The presented work results from ongoing cross-border re- search collaborations initiated with data collection and joint interpretation in mind. A detailed account of the current state, characteristics and spatial and temporal coverage of the European Flood Database, is presented. At this stage, the hydrological data collection is still growing and consists at this time of annual maximum and daily mean discharge series, from over 7000 hydrometric stations of various data series lengths. Moreover, the database currently comprises data from over 50 different data sources. The time series have been obtained from different national and regional data sources in a collaborative effort of a joint European flood research agreement based on the exchange of data, models and expertise, and from existing international data collections and open source websites. These ongoing efforts are contributing to advancing the understanding of regional flood processes beyond individual country boundaries and to a more coherent flood research in Europe.
The current work addresses one of the key building blocks towards an improved understanding of fl... more The current work addresses one of the key building blocks towards an improved understanding of flood processes and associated changes in flood characteristics and regimes in Europe: the development of a comprehensive, extensive European flood database. The presented work results from ongoing cross-border research collaborations initiated with data collection and joint interpretation in mind. A detailed account of the current state, characteristics and spatial and temporal coverage of the European Flood Database, is presented. At this stage, the hydrological data collection is still growing and consists at this time of annual maximum and daily mean discharge series, from over 7000 hydrometric stations of various data series lengths. Moreover, the database currently comprises data from over 50 different data sources. The time series have been obtained from different national and regional data sources in a collaborative effort of a joint European flood research agreement based on the e...
The dynamical evolution of the flood response to landscape-climate feedbacks is evaluated in a jo... more The dynamical evolution of the flood response to landscape-climate feedbacks is evaluated in a joint nonlinear statistical-dynamical approach. For that purpose, a spatiotemporal sensitivity analysis is conducted on hydrological data from 1976-2008 over 804 catchments throughout Austria, and a general, data-independent nonlinear dynamical model is built linking floods with climate (via precipitation), landscape (via elevation) and their feedbacks. These involve nonlinear scale interactions, with landform evolution processes taking place at the millennial scale (slow dynamics), and climate adjusting in years to decades (fast dynamics). The results show that floods are more responsive to spatial (regional) than to temporal (decadal) variability. Catchments from dry lowlands and high wetlands exhibit similarity between the spatial and temporal sensitivities (spatiotemporal symmetry) and low landscape-climate codependence, suggesting they are not coevolving significantly. However, intermediate regions show differences between those sensitivities (symmetry breaks) and higher landscapeclimate codependence, suggesting undergoing coevolution. The break of symmetry is an emergent behaviour from nonlinear feedbacks within the system. A new coevolution index is introduced relating spatiotemporal symmetry with relative characteristic celerities, which need to be taken into account in hydrological space-time trading. Coevolution is expressed here by the interplay between slow and fast dynamics, represented respectively by spatial and temporal characteristics. The dynamical model captures emerging features of the flood dynamics and nonlinear landscape-climate feedbacks, supporting the nonlinear statistical assessment of spatiotemporally asymmetric flood change. Moreover, it enables the dynamical estimation of flood changes in space and time from the given knowledge at different spatiotemporal conditions. This study ultimately brings to light emerging signatures of change in floods arising from nonlinear slow-fast feedbacks in the landscape-climate dynamics, and contributes towards a better understanding of spatiotemporal flood changes and underlying nonlinearly interacting drivers.
There has been a surprisingly large number of major floods in the last years around the world, wh... more There has been a surprisingly large number of major floods in the last years around the world, which suggests that floods may have increased and will continue to increase in the next decades. However, the realism of such changes is still hotly discussed in the literature. This overview article examines whether floods have changed in the past and explores the driving processes of such changes in the atmosphere, the catchments and the river system based on examples from Europe. Methods are reviewed for assessing whether floods may increase in the future. Accounting for feedbacks within the human-water system is important when assessing flood changes over lead times of decades or centuries. It is argued that an integrated flood risk management approach is needed for dealing with future flood risk with a focus on reducing the vulnerability of the societal system.
The June 2013 flood in the Upper Danube Basin, and comparisons with the 2002, 1954 and 1899 floods
The June 2013 flood caused significant damage in Austria. The main reasons for the extraordinary ... more The June 2013 flood caused significant damage in Austria. The main reasons for the extraordinary discharges were high precipitation at the northern fringe of the Alps along with high antecedent soil moisture. Snowfall at high altitudes reduced the runoff volume produced. At the confluence of the Bavarian Danube and the Inn, the small time lag between the two flood waves exacerbated the downstream flood at the Austrian Danube. Because of the long duration and less inundation, there was less flood peak attenuation along the Austrian Danube reach than for the August 2002 flood. The maximum flood discharge of the Danube at Vienna was about 11000 m³/s, as compared to 10300, 9600 and 10500 m³/s in 2002, 1954 and 1899, respectively. This paper reviews the meteorological and hydrological characteristics of the event and compares them with those of the three biggest floods in the past 200 years. The paper discusses whether floods are generally increasing as well as the implications of the recent flood for flood risk management. h l , Th. N e s t e r, J. K o m m a , J. P a r a j k a und R. A.P. P e rd i g ã o , Wien
Non-Gaussianity and Asymmetric Correlation between NAO and Winter Precipitation over the Euro-Atlantic Region
SUMMARY The present work assesses Non-Gaussianity and asymmetry within the statistical response o... more SUMMARY The present work assesses Non-Gaussianity and asymmetry within the statistical response of the monthly winter (December - February) precipitation to the North Atlantic Oscillation (NAO) over the North Atlantic European Region (NAE). In order to evaluate asymmetry, data is split through the median of the NAO index and side correlations are computed for each regime (NAO- and NAO+). Statistically
Monthly Weather Review, 2007
The present work assesses non-Gaussianity and asymmetry within the statistical response of the mo... more The present work assesses non-Gaussianity and asymmetry within the statistical response of the monthly winter (December-February) precipitation to the North Atlantic Oscillation (NAO) over the North Atlantic-European region (NAE). To evaluate asymmetry, data are split through the median of the NAO index and side correlations are computed for each regime [negative and positive phases of the NAO (NAOϪ and NAOϩ, respectively)]. The following statistically significant differences between these correlations are found: (a) near the central North Atlantic, around 40°N, 20°W, and southeast of Iceland, with much stronger correlations in the wet-favorable regime: NAOϪ in the first location and NAOϩ in the second location; (b) around 42°N, 48°W in the west North Atlantic; and (c) south of Greenland and in the west Mediterranean near 36°N, where, in both cases, the correlation is only relevant for the dry-favorable NAOϩ regime. Based on the above decomposition, a map of a statistical test of asymmetry, applicable for every bivariate distribution, is shown.
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Papers by Rui A P Perdigao