Evaluation of two hydro-meteorological ensemble strategies for flash flood forecasting over a catchment of the eastern Pyrenees

This study aims at evaluating the performances of flash flood forecasts issued from deterministic and ensemble meteorological prognostic systems. The hydro-meteorological modeling chain includes the Weather Research and Forecasting model (WRF) forcing the rainfall-runoff model MARINE dedicated to flash flood. Two distinct ensemble prediction systems accounting for (i) perturbed initial and lateral boundary conditions of the meteorological state and (ii) mesoscale model physical parameterizations, have been implemented on the Agly catchment of the Eastern Pyrenees with three sub-catchments exhibiting different rainfall regimes. Different evaluations of the performance of the hydro-meteorological strategies have been performed: (i) verification of short-range ensemble prediction systems and corresponding stream flow forecasts, for a better understanding of how forecasts behave, (ii) usual measures derived from a contingency table approach, to test an alert threshold exceedance, and (iii) overall evaluation of the hydro-meteorological chain using the Continuous Rank Probability Score, for a general quantification of the ensemble performances. Results show that the overall discharge forecast is improved by both ensemble strategies with respect to the deterministic forecast. Threshold exceedance detections for flood warning also benefit from large hydro-meteorological ensemble spread. There are no substantial differences between both ensemble strategies on these test cases in terms both of the issuance of flood warnings and the overall performances, suggesting that both sources of external-scale uncertainty are important to take into account

Potentiality of hydrometeorological ensemble forecasting of flash floods for risk assessment: Application to the Agly catchment (Eastern Pyrenees)

The Western Mediterranean region is prone to heavy precipitations resulting in devastating flash floods. In order to improve the predictability of this kind of events and to increase the forecasting lead time, accurate predictions of small-scale convective systems are needed. But quantitative precipitation forecasts (QPFs) are arduous due to the uncertainties arising from both the physical parameterizations of numerical weather prediction models and the representation of the atmospheric states. These uncertainties can result in deficient QPFs for hydrological forecasting purposes, especially over small-to-medium sized basins. Nowadays, short-range ensemble prediction systems (EPSs) provide the state-of-art framework to generate quantitative discharge forecasts (QDFs) and to cope with the different sources of external-scale uncertainties. We examine the performance of two distinct hydrological EPSs (HEPSs), specially designed to explicitly cope with uncertainties in the initial and lateral boundary conditions of the meteorological state (IC/LBCs), and model physical parameterizations (MPS). Deterministic and probabilistic 48 h atmospheric forecasts have been generated using the Weather Research and Forecasting (WRF) model. This study focuses on a catchment of the Eastern Pyrenees, the Agly catchment, as a test case for implementing the ensemble hydro-meteorological predictions. With a drainage area of 1050 km2, the Agly is the second coastal river of the Eastern Pyrenees. It originates from an elevation of approximately 700 m and drains the Pyrenees foothills. It flows into the Mediterranean Sea at Barcarès with a length of around 80 km. A dam dedicated to flood and water management controls approximately 400 km2 of the catchment. The MARINE distributed model, flash-flood dedicated and process-oriented, has been chosen for this study. This model has been extensively tested on a large panel of hydrologic behaviors around the French Mediterranean area. WRF-driven QPFs have been used to feed the MARINE hydrological model for the medium-size Agly river basin as a support tool for early warning and mitigation strategies. We also explore the uncertainty transference from the atmospheric context down to the hydrological system. Results highlight the benefits of accounting for uncertainties in QPFs and the value of the proposed set-up for the short-range forecasting of floods. Combination of both ensembles (hydrological and meteorological) helps limiting a possible inadequacy of calibrated set of parameters on one hand and takes into account meteorological and parametric uncertainties on the other hand

A comparison of ensemble strategies for flash flood forecasting: The 12 October 2007 case study in Valencia, Spain

On 12 October 2007, several flash floods affected the Valencia region, eastern Spain, with devastating impacts in terms of human, social, and economic losses. An enhanced modeling and forecasting of these extremes, which can provide a tangible basis for flood early warning procedures and mitigation measures over the Mediterranean, is one of the fundamental motivations of the international Hydrological Cycle in the Mediterranean Experiment (HyMeX) program. The predictability bounds set by multiple sources of hydrological and meteorological uncertainty require their explicit representation in hydrometeorological forecasting systems. By including local convective precipitation systems, short-range ensemble prediction systems (SREPSs) provide a state-of-the-art framework to generate quantitative discharge forecasts and to cope with different sources of external-scale (i.e., external to the hydrological system) uncertainties. The performance of three distinct hydrological ensemble prediction systems (HEPSs) for the small-sized Serpis River basin is examined as a support tool for early warning and mitigation strategies. To this end, the Flash-Flood Event-Based Spatially Distributed Rainfall-RunoffTransformation-Water Balance (FEST-WB) model is driven by ground stations to examine the hydrological response of this semiarid and karstic catchment to heavy rains. The use of a multisite and novel calibration approach for the FEST-WB parameters is necessary to cope with the high nonlinearities emerging from the rainfall-runofftransformation and heterogeneities in the basin response. After calibration, FEST-WB reproduces with remarkable accuracy the hydrological response to intense precipitation and, in particular, the 12 October 2007 flash flood. Next, the flood predictability challenge is focused on quantitative precipitation forecasts (QPFs). In this regard, three SREPS generation strategies using the WRF Model are analyzed. On the one side, two SREPSs accounting for 1) uncertainties in the initial conditions (ICs) and lateral boundary conditions (LBCs) and 2) physical parameterizations are evaluated. An ensemble Kalman filter (EnKF) is also designed to test the ability of ensemble data assimilation methods to represent key mesoscale uncertainties from both IC and subscale processes. Results indicate that accounting for diversity in the physical parameterization schemes provides the best probabilistic high-resolution QPFs for this particular flash flood event. For low to moderate precipitation rates, EnKF and pure multiple physics approaches render undistinguishable accuracy for the test situation at larger scales. However, only the multiple physics QPFs properly drive the HEPS to render the most accurate flood warning signals. That is, extreme precipitation values produced by these convective-scale precipitation systems anchored by complex orography are better forecast when accounting just for uncertainties in the physical parameterizations. These findings contribute to the identification of ensemble strategies better targeted to the most relevant sources of uncertainty before flash flood situations over small catchments

NRCS-CN estimation from onsite and remote sensing data for management of a reservoir in the Eastern Pyrenees

Onsite and Earth observation (EO) data are used for the calibration of the Natural Resources Conservation Service curve number (NRCS-CN) value in a hydrological simulation model. The model was developed for La Muga catchment (eastern Pyrenees) highly vulnerable to flood and drought episodes. It is an integral part of a regional reservoir management tool, which aims at minimizing the flood risk while maximizing the preservation of water storage. The CN values were optimized for five recorded events for the model to match the observed hydrographs at the reservoir when supported with the measured rainfall intensities. This study also investigates the possibilities of using antecedent moisture conditions (AMC) retrieved from satellite data to inform the selection of the NRCS-CN losses parameter. A good correlation was found between the calibrated CN values and the AMC obtained from satellite data. This correlation highlights the interest in using EO data to update NRCS-CN estimates. This advances in hydrologic-hydraulic coupled modeling combined with new remote sensing datasets present valuable opportunities and potential benefits for flood risk management and water resources preservation

Large wood debris that clogged bridges followed by a sudden release: the 2019 flash flood in Catalonia

The aim is the reconstruction of the October 2019 flash flood, that was documented through extensive field work: rainfall (300 mm in just a few hours), flood marks, times of flood passage and witnesses' snapshots and reports, channel changes, log drift (20,000 trees) and woody debris at bridges, as well as large damage and six fatalities. The methods are: hydrological model built for the rainfall-runoff in the basin and the flood routing in the river, use of hydraulic principles such as flow at waterfalls, flow against obstacles (trees), etc. and finally 1D/2D free surface numerical models. The uppermost 100 km2 produced discharges of 700 m3/s (up to 50 m3/s/km2, locally). Three bridges failed, but their cascading failure (when one failure triggers the next one downstream) was not proved. The main channel widened more than 10 times, dragging away soil and vegetation like a bulldozer. The resulting large wood debris that clogged two bridges worsened the inundation. An anomalous flow downstream, probably a surge of around 1090 m3/s, due to the failure of a woody jam at a narrow bridge, took two lives. Water Authority is now warning flood planners that vegetated, torrential basins may cause catastrophic floods in the valley towns, if their narrow bridges are sensitive to woody debris.Catalan Water Authority and its Tarragona officers, Meteoprades and Fons Signatus, Joan March and a number of witnesses. The UPC's contribution was funded by the contract CTN2000029 of the “Agència Catalana de l′Aigua”. The UB's contribution has been developed within the framework of the AGORA project, funded by the "Agència Catalana de l′Aigua". Our thanks to the "Museu de la Vida Rural", in l′Espluga de Francolí, and all the citizens who contributed to the return of experience. The UIB's research has been supported by the Ministerio de Ciencia, Innovación y Universidades (CGL2017-82868-R and PID2020-113036RB-I00/AEI/10.13039/501100011033 research projects, which are partially supported by the European Regional Development Funds).Peer ReviewedPostprint (published version

Hydrometeorological numerical simulations of western Mediterranean severe precipitation events

[cat] La societat humana i les seves propietats materials són essencialment elements fràgils, susceptibles de patir episodis catastròfics causats pel Medi Ambient. Aquests episodis es presenten de manera més freqüent en determinades àrees i poden tenir un gran impacte en zones densament poblades, produint importants danys. Aproximadament el 60% d’aquests desastres estan relacionats amb huracans i inundacions. Les inundacions al sud d’Europa, i més concretament a la costa de la Mediterrània Occidental, poden ser extremadament violentes i s’experimenten en zones urbanes molt freqüentment en el temps i de manera aleatòria en l’espai, sobretot durant la tardor. Les inundacions sobtades es distingeixen de les inundacions ’ordinàries’ per l’escala temporal en la qual es desenvolupen: es poden produir en unes quantes hores, o menys, després de fortes pluges i passen en massa poc temps per intentar la mitigació dels danys. Una inundació és un episodi hidrometeorològic ja que depèn de factors hidrològics i meteorològics. Els factors meteorològics són bàsics quan la pluja és intensa i aquesta intensitat es manté durant el temps necessari per produir una potencial inundació sobtada. Els factors hidrològics també són fonamentals en aquest tipus d’events, ja que s’han de tenir en compte factors com: la precipitació prèvia, i per tant, la humitat prèvia del sòl; la permeabilitat d’aquest; el pendent del terreny; els usos del sòl i la cobertura de la vegetació. Per tant, la predicció i l’estudi d’aquestes inundacions implica simulacions tan hidrològiques com meteorològiques. Avui en dia, els models meteorològics d’àrea limitada (LAMs) produeixen una discretització espacial de pocs km2 i parametritzen la pluja sobre finestres espacials del mateix tamany. Aquest estatus actual permet que siguin eines apropiades per a propòsits hidrològics i eines bàsiques per a disparar sistemes d’alerta davant possibles inundacions a la Mediterrània Occidental. Però també s’han de tenir en compte les diferents fonts d’incertesa presents en les formulacions d’aquests models, incloent les provinents de les condicions inicials i de contorn i del salt que encara és present entre les escales que resolen ambdós models. Tenint en compte tots aquests factors, en aquesta Tesi s’han examinat dues qüestions de màxim interès. Primer, explorar la possibilitat d’obtenir simulacions precises dels increments de cabal i dels seus màxims, o almenys, si aquestes simulacions de l’escorrentia podrien ser capaces d’arribar als llindars adequats per a produir una activació de la gestió dels sistemes d’emergència. Segon, avaluar l’impacte de les incerteses abans esmentades en la cadena hidrometeorològica. Algunes eines meteorològiques emprades per a estudiar l’impacte d’aquestes incerteses també són discutides. Com s’ha esmentat, la precipitació és indubtablement la variable més crítica en el Mediterrani Espanyol degut als seus impactes socials i econòmics tant pel que fa al present com pel que fa al futur. La seva escassetat durant els mesos d’estiu i l’elevada activitat turística reflecteixen un accentuat estrès hidrològic, especialment en anys anormalment secs. Nombrosos estudis han assenyalat que els períodes de pluja s’han escurçat les darreres dècades degut a les conseqüències del canvi climàtic en algunes parts de la Mediterrània. Avui en dia, els models de circulació general (GCMs) són l’eina fonamental per a la simulació del clima i l’avaluació del canvi climàtic. Encara que incorporen les característiques principals dels patrons de circulació global, el rendiment de les simulacions del clima present són bastant pobres quan les seves projeccions s’apliquen a escales regionals. La regionalització dinàmica aplicada a les sortides dels GCMs intenta tenir en compte els efectes dels forçaments de mesoscala, nidificant models d’àrea limitada de més alta resolució damunt àrees específiques d’interès. Un augment de la resolució horitzontal i de la freqüència temporal de les sortides dels GCMs –que alimenten els models d’àrea limitada– sembla ser una estratègia raonable a seguir, però no queda clar si aquesta és l’estratègia òptima, especialment en àrees com el Mediterrani Espanyol, on l’orografia té un paper tan important. Per tant, un altre objectiu de la Tesi és estudiar la sensibilitat de les simulacions numèriques mesoscalars de la precipitació a les entrades dels models de llarga escala. A més a més, la regionalització dinàmica de la precipitació des dels models de circulació global a regional és un pas preliminar –i fonamental– a l’acoblament entre models meteorològics i hidrològics. Per tant, aquesta qüestió ha estat examinada en termes de la sensibilitat a la resolució espacial i temporal de la regionalització dinàmica dels models globals a regionals pel Mediterrani Espanyol, una àrea altament vulnerable d’acord amb la majoria dels escenaris de canvi climàtic

Com es resol la preservació de la fertilitat en adolescents oncològics, i quin és el paper dels professionals sanitaris en aquest procés?

[cat] Els i les adolescents amb càncer es troben en una situació molt complicada per la seva curta edat, en què han de passar per les diferents etapes de la adolescència així com per les diferents fases del càncer. A més, han de plantejar-se tot el que comporta el càncer així com múltiples aspectes del futur, com és la preservació de la fertilitat, aspectes que en condicions normals no es plantejarien i que suposen un gran responsabilitat per l’edat que tenen. Per tant, sorgeix la necessitat d’investigar les diferents opcions de preservació de la fertilitat en adolescents oncològics. Existeixen diferents opcions, en què la criopreservació d’embrions i d’ovòcits per part del sexe femení i el banc de semen per part del sexe masculí, són les opcions més estandarditzades. També, és d’interès investigar qui té la responsabilitat de decisió en la preservació, en què els i les adolescents haurien de decidir per si sols, encara que es troben influïts tant pels professionals sanitaris com pels seus pares. Però, l’objectiu principal és determinar com és resol la preservació de la fertilitat i quin és el paper dels professionals sanitaris en el procés. L’evidència mostra que es realitza un abordatge inadequat per part dels professionals sanitaris, en què existeixen múltiples barreres, però hi ha un desig de millora per part dels professionals. Encara que, per resoldre adequadament la preservació de la fertilitat és necessari un treball en equip multidisciplinari.[eng] Adolescents suffering from cancer face a very complicated situation due to their young age. During this age they have to deal with both the different adolescence stages and the cancer stages. Furthermore, they have to consider all what cancer involves and multiple aspects about the future, such as the fertility preservation; aspects that in normal conditions they would not have to think about and which imply a lot of responsibility at their ages. Thus, the necessity of investigating the different options of fertility preservation on oncologic adolescents emerges. There are different options and the ones in which the cryopreservation of embryo and oocytes from women and the semen bank from men play an important role are the most standardized. It is also of interest to study who is the responsible one at the time of making the decision regarding with preservation: adolescents should decide by their own, although they are influenced either by the healthcare professionals or their parents. However, the lead aim is to determine how to solve the fertility preservation and which role the healthcare professionals play in this process. Evidence shows that healthcare professionals do an inadequate approach with regard to this issue: there are multiple borders, but there is a desire of improvement from healthcare professionals. Nevertheless, to solve the fertility preservation in a suitable manner it is necessary a multidisciplinary teamwork

A statistical adjustment of regional climate model outputs to local scales: Application to Platja de Palma, Spain

Peer Reviewe

Projections of the climate potential for tourism at local scales: Application to Platja de Palma, Spain

Primary socioeconomic activities in the System of Platja de Palma (SPdP), located in the southwestern coast of Mallorca, Spain, are beach-based holidays and, therefore, are very closely linked to climate. The social, economic and environmental adaptation that this region must make in the mid- and long-term period has to take into account the changes in the tourist potential when the climate changes. A second-generation climate index for tourism (CIT) has been adopted to measure tourism potential under the present and possible future climatic conditions. CIT is a theoretically based and empirically derived index that allows assessing the sun, sea and sand (3S) weather resource. Daily observed series of 2 m maximum temperature, precipitation, 2 m relative humidity, cloud cover and 10 m wind speed have been used to derive the present climate potential for tourism. For future projections, daily averaged meteorological variables have been obtained from a set of regional climate models (RCMs) within the European ENSEMBLES project. The adoption of a multimodel ensemble strategy allows quantifying the uncertainties arising from model errors and boundary conditions. To use CIT values based on RCM data properly at local scales, a quantile-quantile adjustment has been applied. Results show a significant increase in the annual frequency of days with acceptable conditions together with a slightly increment for the ideal climate perceptions at the expense of decreasing unacceptable categories. For the summery peak season, ideal conditions are projected to decrease from mid-century favouring acceptable categories. However, an almost general increase for both classes is anticipated in spring and autumn throughout the century. That is, higher frequencies of optimal climate perceptions for carrying out 3S outdoors activities are expected to shift from the peak to shoulder seasons. Therefore, climate change would result in a major impact for the current seasonally adjusted service sector in SPdP. With this information at hand, policy makers and the team of experts planning its socioeconomic future can respond more effectively to the demanding challenge of local adaptation to climate change by implementing adaptation and mitigation strategies to the tourist sector. © 2011 Royal Meteorological Society.Peer Reviewe

Daily precipitation records over mainland Spain and the Balearic Islands

Understanding the spatial distribution of extreme precipitations is of major interest in order to improve our knowledge of the climate of a region and its relationship with society. These analyses inevitably require the use of directly observed values to account for the actual extreme amounts rather than analyzed gridded values. A study of daily rainfall extremes observed over mainland Spain and the Balearic Islands is performed by using records from 8135 rain gauge stations from the Spanish Weather Agency (AEMET). Results show that the heaviest daily precipitations have been observed mainly on the coastal Mediterranean zone from Gibraltar to the Pyrenees. In particular, a record value of 817 mm was recorded in the Valencia region in 1987. The current map of daily records in Spain, which updates the pioneering work of the Spanish meteorologist Font, shows similar distribution of extreme events but with notably higher amounts. Generalized extreme values distributions fit the Mediterranean and Atlantic rain gauge measurements and shows the different characteristics of the extreme daily precipitations in both regions. We identify the most extreme events (above 500 mm per day) and provide a brief description of a typical meteorological situation in which these damaging events occur. An analysis of the low-level circulation patterns producing such extremes - by means of simple indices such as NAO, WeMOi and IBEI - confirms the relevance of local flows in the generation of either Mediterranean or Atlantic episodes. WeMOi, and even more IBEI, are good discriminants of the region affected by the record precipitation event. © Author(s) 2013. CC Attribution 3.0 License.Peer Reviewe