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  • Evaluation of hazard assessment nowcasting at European scale within the HAREN project

     Berenguer Ferrer, Marc; Sempere Torres, Daniel
    Geophysical research abstracts
    Date of publication: 2014-04
    Journal article

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    In this work we present the results of the evaluation of the HAREN nowcasting system during summer and fall 2013, not only in terms of point and regional rainfall forecasts, but in terms of the skill in forecasting the hazard levels as well.

  • Analysis of the uncertainty in rainfall forecasts obtained with a probabilistic nowcasting technique

     Buil Martinez, Alejandro; Berenguer Ferrer, Marc; Sempere Torres, Daniel
    Geophysical research abstracts
    Date of publication: 2014-04
    Journal article

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    Nowadays different methodologies have been developed for very short-term precipitation forecasting based on radar observations. When the advection of precipitation explains a signi¿cant portion of the temporal evolution of precipitation, the Lagrangian persistence is the most appropriate method. Unfortunately, in convective precipitation episodes it does not occur like this because the growth and decay of precipitation is generally fast and advection provides little information. It is then necessary to introduce probabilistic nowcasting methods that allow to characterize the uncertainty associated with the temporal evolution of precipitation. SBMcast (Berenguer et al., 2011) is an ensemble nowcasting algorithm based on Lagrangian extrapolation of recent radar observations. It generates a set of future rainfall scenarios (ensemble members) compatible with the observations and preserving the spatial and temporal structure of the rainfall ¿eld according to the String of Beads model. The parameters used to generate a member of the ensemble model are the time series of a set of variables that model the rainfall ¿eld at two levels: at global and at pixel scale. We have analyzed these two components of SBMcast with the aim of identifying the role that each component has in the resulting forecast uncertainty. The ¿nal objective of this analysis is understanding the expected impact of the use of additional information to constrain each part of the algorithm. Conventional scores have been used to compare SBMcast with two reference algorithms: deterministic Lagrangian extrapolation, and the probabilistic ¿Local Lagrangian¿ technique [the one that demonstrated the best skill, among those analyzed by Germann and Zawadzki (2004)]. The results have been obtained for a set of rainfall episodes in the vicinity of Barcelona, Catalonia (Spain) using the observations of the Catalan Weather Service radar network.

  • An operational flood warning system for poorly gauged basins: demonstration in the Guadalhorce basin (Spain)

     Versini, Pierre-Antoine; Berenguer Ferrer, Marc; Corral Alexandri, Carles; Sempere Torres, Daniel
    Natural hazards
    Date of publication: 2013-11-01
    Journal article

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    This paper deals with the presentation of a flood warning system (GFWS) developed for the specific characteristics of the Guadalhorce basin (3,200 km2, SE of Spain), which is poorly gauged and often affected by flash and plain floods. Its complementarity with the European flood alert system (EFAS) has also been studied. At a lower resolution, EFAS is able to provide a flood forecast several days in advance. The GFWS is adapted to the use of distributed rainfall maps (such as radar rainfall estimates), and discharge forecasts are computed using a distributed rainfall¿runoff model. Due to the lack of flow measurements, the model parameters calibrated on a small watershed have been transferred in most of the basin area. The system is oriented to provide distributed warnings and fulfills the requirements of ungauged basins. This work reports on the performance of the system on two recent rainfall events that caused several inundations. These results show how the GFWS performed well and was able to forecast the location and timing of flooding. It demonstrates that despite its limitations, a simple rainfall¿runoff model and a relatively simple calibration could be useful for event risk management. Moreover, with low resolution and long anticipation, EFAS appears as a good complement tool to improve flood forecasting and compensate for the short lead times of the GFWS

    This paper deals with the presentation of a flood warning system (GFWS) developed for the specific characteristics of the Guadalhorce basin (3,200 km2, SE of Spain), which is poorly gauged and often affected by flash and plain floods. Its complementarity with the European flood alert system (EFAS) has also been studied. At a lower resolution, EFAS is able to provide a flood forecast several days in advance. The GFWS is adapted to the use of distributed rainfall maps (such as radar rainfall estimates), and discharge forecasts are computed using a distributed rainfall–runoff model. Due to the lack of flow measurements, the model parameters calibrated on a small watershed have been transferred in most of the basin area. The system is oriented to provide distributed warnings and fulfills the requirements of ungauged basins. This work reports on the performance of the system on two recent rainfall events that caused several inundations. These results show how the GFWS performed well and was able to forecast the location and timing of flooding. It demonstrates that despite its limitations, a simple rainfall–runoff model and a relatively simple calibration could be useful for event risk management. Moreover, with low resolution and long anticipation, EFAS appears as a good complement tool to improve flood forecasting and compensate for the short lead times of the GFWS.

  • Precipitation nowcasting and warning at European scale

     Berenguer Ferrer, Marc; Sempere Torres, Daniel
    Geophysical research abstracts
    Date of publication: 2013
    Journal article

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  • A comparison between two probabilistic radar-based nowcasting methods

     Buil Martinez, Alejandro; Berenguer Ferrer, Marc; Sempere Torres, Daniel
    Geophysical research abstracts
    Date of publication: 2013
    Journal article

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  • Compositing radar reflectivity observations with an inverse method

     Roca Sancho, Jordi; Berenguer Ferrer, Marc; Sempere Torres, Daniel
    Geophysical research abstracts
    Date of publication: 2013
    Journal article

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  • Hydrological impact of forest fires and climate change in a Mediterranean basin

     Versini, Pierre-Antoine; Velasco, M.; Cabello, A.; Sempere Torres, Daniel
    Natural hazards
    Date of publication: 2013-03
    Journal article

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  • Tractament de la incertesa en estimació i previsió de pluja amb radars meteorològics  Open access

     Roca Sancho, Jordi
    Defense's date: 2013-10-16
    Department of Geotechnical Engineering and Geo-Sciences, Universitat Politècnica de Catalunya
    Theses

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    Aquesta tesi aborda la incertesa en l¿estimació i previsió de pluja amb radars meteorològics en dos sentits: la seva quantificació de manera probabilística, i la reducció dels seus efectes en les estimacions de pluja.Una manera directa d¿obtenir una quantificació de la incertesa és aproximar l¿error comès en l¿estimació o previsió de pluja per comparació amb una referència, i analitzar l¿error. En aquesta tesi es proposen mètodes per caracteritzar estadísticament l¿error en estimació i previsió de pluja amb radar meteorològics. En particular, la caracterització de l¿error està enfocada a la representació de la incertesa mitjançant la generació de múltiples realitzacions de l¿estimació o la previsió, de manera que cada realització sigui un possible camp de pluja. Aquests conjunts de realitzacions (ensembles) són fàcils d¿interpretar i d¿usar com a entrada en altres sistemes per a l¿anàlisi de la propagació de la incertesa a través d¿un sistema no lineal (per exemple models hidrològics de transformació pluja-escolament).Al llarg del temps, els esforços per reduir la incertesa en les estimacions de pluja s¿han centrat, en general, en la correcció de les observacions radar per radar, i encara no s¿ha treballat a fons el potencial de les xarxes de radars actuals en les àrees cobertes per més d¿un radar. En aquesta tesi es presenta un mètode per obtenir, aprofitant mesures de diversos radars sobre una mateixa zona, un camp tridimensional de reflectivitat més acurat que els dels mètodes tradicionals. Per això també s¿ha desenvolupat una metodologia d¿avaluació de mètodes de composició tridimensional d¿observacions de radars.

    This thesis deals with uncertainty in radar-based precipitation estimation and nowcasting in two ways: its quantification in a probabilistic manner, and its reduction in the precipitation estimates. A straightforward way to obtain a quantification of the uncertainty is approximating the error in rainfall estimates or nowcasts by comparison against a reference and analyzing the error. In this thesis methods for the error statistical characterization in both rainfall estimation and nowcasting are proposed. In particular, the error characterization is thought for the uncertainty representation by means of the generation of multiple realizations of the estimates or nowcasts, being each realization a possible rainfall field. These sets of realizations (ensembles) are easy to interpret and use as an input in other non-linear systems (for instance, rainfall-runoff hydrological models) for the analysis of the uncertainty propagation. Through the years, the efforts to reduce the uncertainty in rainfall estimates have been devoted, in general, to the correction of radar observations for individual radars. The potential of radar networks in regions covered with several radars has not been fully exploited yet. In this thesis, we present a method to improve the estimation of 3D reflectivity fields using observations from several radars. An evaluation methodology has been also developed to compare different 3D radar mosaicking techniques.

    Aquesta tesi aborda la incertesa en lʼestimació i previsió de pluja amb radars meteorològics en dos sentits: la seva quantificació de manera probabilística, i la reducció dels seus efectes en les estimacions de pluja. Una manera directa dʼobtenir una quantificació de la incertesa és aproximar lʼerror comès en lʼestimació o previsió de pluja per comparació amb una referència, i analitzar lʼerror. En aquesta tesi es proposen mètodes per caracteritzar estadísticament lʼerror en estimació i previsió de pluja amb radar meteorològics. En particular, la caracterització de lʼerror està enfocada a la representació de la incertesa mitjançant la generació de múltiples realitzacions de lʼestimació o la previsió, de manera que cada realització sigui un possible camp de pluja. Aquests conjunts de realitzacions (ensembles) són fàcils dʼinterpretar i dʼusar com a entrada en altres sistemes per a lʼanàlisi de la propagació de la incertesa a través dʼun sistema no lineal (per exemple models hidrològics de transformació pluja-escolament). Al llarg del temps, els esforços per reduir la incertesa en les estimacions de pluja sʼhan centrat, en general, en la correcció de les observacions radar per radar, i encara no sʼha treballat a fons el potencial de les xarxes de radars actuals en les àrees cobertes per més dʼun radar. En aquesta tesi es presenta un mètode per obtenir, aprofitant mesures de diversos radars sobre una mateixa zona, un camp tridimensional de reflectivitat més acurat que els dels mètodes tradicionals. Per això també sʼha desenvolupat una metodologia dʼavaluació de mètodes de composició tridimensional dʼobservacions de radars.

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    Gestió de riscos torrencials: el projecte IMPRINTS  Open access

     Berenguer Ferrer, Marc; Sempere Torres, Daniel
    Gestió de les inundacions
    Presentation's date: 2013-11
    Presentation of work at congresses

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    En aquest article s¿hi presenten els elements necessaris per la generació d¿alertes d¿inundacions torrencials en temps real, prenent com a exemple l¿eina desenvolupada en el Projecte del 7è Programa Marc ¿IMproving Preparedness and RIsk maNagemenT for flash floods and debriS flow events¿ (FP7-ENV-2008-1-IMPRINTS 226555)

    En aquest article s’hi presenten els elements necessaris per la generació d’alertes d’inundacions torrencials en temps real, prenent com a exemple l’eina desenvolupada en el Projecte del 7è Programa Marc “IMproving Preparedness and RIsk maNagemenT for flash floods and debriS flow events” (FP7-ENV-2008-1-IMPRINTS 226555)

    Postprint (author’s final draft)

  • From rainfall nowcasting to rainfall hazard assessment

     Sempere Torres, Daniel; Berenguer Ferrer, Marc
    International Precipitation Conference
    Presentation's date: 2013-07-02
    Presentation of work at congresses

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  • Coexistence of meteorological radars and wind farms: successful operational stories

     Sempere Torres, Daniel; Berenguer Ferrer, Marc; Zawadzki, Isztar
    Conference on Radar Meteorology
    Presentation's date: 2013-09-19
    Presentation of work at congresses

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  • The challenge of transforming rainfall nowcasting into rainfall hazard assessment

     Sempere Torres, Daniel; Berenguer Ferrer, Marc
    Conference on Radar Meteorology
    Presentation's date: 2013-09-17
    Presentation of work at congresses

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  • Improving 3-D reflectivity radar mosaics using an inverse method

     Berenguer Ferrer, Marc; Roca Sancho, Jordi; Sempere Torres, Daniel
    Conference on Radar Meteorology
    Presentation's date: 2013-09-19
    Presentation of work at congresses

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    Mosaicking volumetric reflectivity observations from multiple radars over a common domain is supposed to improve the quality of Quantitative Precipitation Estimates by reducing the effects of path attenuation by intense precipitation, beam blockage or the vertical profile of reflectivity. So far, composites of radar observations are commonly carried out through simple criteria (by picking the closest observation or the maximum value...) or using quality indices that need a priori definition of quality descriptors. This work proposes a methodology to retrieve the 3-D Cartesian reflectivity field most compatible with the observations from the different radars of the network. The methodology follows the concept of an inverse method based on the minimization of a cost function that penalizes discrepancies between simulated and actual observations for each radar of the network. The simulations are obtained with a model that simulates the radar sampling of the atmosphere, simulating the effects of distance (beam broadening and increasing of the sampling height) and path attenuation by intense precipitation. The model considers the specific characteristics of the radars (location, scanning strategy, frequency, beam width, pulse length...). The methodology has been applied to the network of C-band radars in the vicinity of Barcelona, Spain. The retrievals have been obtained from the volumetric reflectivity observations of two radars. The evaluation of the retrievals has been performed with the observations of a network of rain gauges. Also, observations from an independent radar have been used for verification at different heights. Furthermore, the results are compared with those obtained with conventional mosaicking techniques.

  • Hydrological value of low-cost X-band radars for heavy rain hazard assessment in urban areas: Demonstration experiment in Barcelona

     Sempere Torres, Daniel; Berenguer Ferrer, Marc; Pfeifer, Monika
    International Conference on Flood Resilience: Experiences in Asia and Europe
    Presentation's date: 2013-09-07
    Presentation of work at congresses

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    Radar-based rainfall nowcasting at European scale: long-term evaluation and performance assessment  Open access

     Berenguer Ferrer, Marc; Sempere Torres, Daniel
    Conference on Radar Meteorology
    Presentation's date: 2013-09-20
    Presentation of work at congresses

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    This work studies the performance of CRAHI's algorithm for rainfall nowcasting at European scale using the mosaics produced within the EUMETNET project OPERA (with a resolution of 4 km and 15 minutes) in the framework of the European Civil Protection research project HAREN (www.haren-project.eu). Systematic evaluation has been carried out since June 2012, focusing on the space-time variability of the nowcasting skills, and its dependence on the scale of the forecasted precipitation systems and on rainfall intensities. Also, the probabilistic nowcasting technique SBMcast (Berenguer et al. 2011) has been adapted to the use of OPERA mosaics at European scale to assess the uncertainty in the produced nowcasts. The performance of this probabilistic technique has been evaluated over a number of cases. Finally, the work analyzes the usefulness of these nowcasts for hazard assessment at European scale, based on exceeding the regional rainfall thresholds used by the EUMETNET project METEOALARM.

    This work studies the performance of CRAHI's algorithm for rainfall nowcasting at European scale using the mosaics produced within the EUMETNET project OPERA (with a resolution of 4 km and 15 minutes) in the framework of the European Civil Protection research project HAREN (www.haren-project.eu). Systematic evaluation has been carried out since June 2012, focusing on the space-time variability of the nowcasting skills, and its dependence on the scale of the forecasted precipitation systems and on rainfall intensities. Also, the probabilistic nowcasting technique SBMcast (Berenguer et al. 2011) has been adapted to the use of OPERA mosaics at European scale to assess the uncertainty in the produced nowcasts. The performance of this probabilistic technique has been evaluated over a number of cases. Finally, the work analyzes the usefulness of these nowcasts for hazard assessment at European scale, based on exceeding the regional rainfall thresholds used by the EUMETNET project METEOALARM.

  • Precipitation nowcasting and warning at European scale

     Berenguer Ferrer, Marc; Sempere Torres, Daniel
    European Geosciences Union General Assembly
    Presentation's date: 2013-04-12
    Presentation of work at congresses

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  • Resilience-Increasing Strategies for Coasts - toolKIT

     Sempere Torres, Daniel
    Participation in a competitive project

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  • Integration of research advances in modelling and monitoring in support of WFD river basin management planning in the context of climate change

     Quevauviller, Phillipe; Barceló Culleres, Damià; Beniston, M.; Djordjevic, S.; Harding, R.J.; Iglesias, A.; Ludwig, R.; Navarra, A.; Navarro Ortega, Alicia; Mark, O.; Roson, R.; Sempere Torres, Daniel; Stoffel, M.; van Lanen, H.A.J.; Werner, M.G.F.
    Science of the total environment
    Date of publication: 2012-12
    Journal article

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  • Benefits and limitations of using the weather radar for the definition of rainfall thresholds for debris flows. Case study from Catalonia (Spain)

     Abanco Martinez de Arenzana, Claudia; Hürlimann Ziegler, Marcel; Sempere Torres, Daniel; Berenguer Ferrer, Marc
    Geophysical research abstracts
    Date of publication: 2012-04
    Journal article

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  • A scenario-incorporating analysis of the propagation of uncertainty to flash flood simulations

     Quintero Duque, Felipe; Sempere Torres, Daniel; Berenguer Ferrer, Marc; Baltas, Evangelos
    Journal of hydrology
    Date of publication: 2012-08
    Journal article

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    This study proposes a methodology to analyze the propagation of uncertainty arising from radar rainfall and model parameter estimation to the flow simulations obtained from flash flood modeling. For this purpose an ensemble approach that describes the error from radar rainfall estimation and a novel approach that considers the seasonality and variability of catchment conditions in the estimation of model parameters have been implemented. The methodology analyzes the separate effect of each sourceof uncertainty and their interaction on runoff simulations. The methodology has been applied in the Besòs river basin, Catalonia (Spain) with a drainage area of 1020 km2. The results show that the effect of parameter estimation uncertainty produces a smaller spread in the model realizations than the effect caused by the uncertainty in rainfall estimation.

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    Adding value to the measurements of an X-band radar on Catalonian coast  Open access

     Berenguer Ferrer, Marc; Sempere Torres, Daniel
    Meteorological Technology International
    Date of publication: 2012-08
    Journal article

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    Rainscanner@Barcelona is an experiment assessing the hydrological value of a small X-band radar in urban areas.

  • Reconstruction of historical precipitation based on radar fields: application on Catalonia region (Spain)

     Versini, Pierre-Antoine; Berenguer Ferrer, Marc; Sempere Torres, Daniel
    Geophysical research abstracts
    Date of publication: 2012-04
    Journal article

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  • Blending of radar and gauge rainfall measurements: a preliminary analysis of the impact of radar errors

     Sempere Torres, Daniel; Berenguer Ferrer, Marc; Velasco Forero, Carlos Alfonso
    Date of publication: 2012-08
    Book chapter

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    Several methodologies have been proposed to combine radar and raingauge measurements with the aim of generating improved quantitative precipitation estimates (QPEs). These methods are based on interpolating point raingauge measurements (implicitly assumed to be “the truth”) and benefiting from the structure of the rainfall field as depicted by the radar. The use of a non-parametric approach based on radar measurements has been recently demonstrated, showing the benefits in the interpolation of raingauge measurements under the hypotheses of the Kriging approach. Several experiments have been carried out over a large number of cases and a variety of regions, Kriging with an external drift (i.e. the radar description of the rainfall field) being the approach showing more robust and (overall) better performance. Here, the impact of the discrepancies between two almost-collocated radars on the blended QPE fields was investigated.

  • Evaluation of the performance of a nowcasting technique using European radar mosaics

     Sempere Torres, Daniel; Berenguer Ferrer, Marc
    WMO/WWRP International Symposium on Nowcasting and Very Short Range Forecasting
    Presentation's date: 2012-08-07
    Presentation of work at congresses

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  • RAINSCANNER@Barcelona : an experiment to assess the hydrological value of a portable X-band radar

     Berenguer Ferrer, Marc; Park, Shinju; Sempere Torres, Daniel; Didszun, Jens; Pool, Marcus; Pfeifer, Monika
    European Conference on Radar in Meteorology and Hydrology
    Presentation's date: 2012-06-25
    Presentation of work at congresses

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  • Improving a blending technique by giving more importance to the growth and decay of the NWP models

     Hernández, Olver; Berenguer Ferrer, Marc; Sempere Torres, Daniel; Sánchez-Diezma Guijarro, Rafael
    European Conference on Radar in Meteorology and Hydrology
    Presentation's date: 2012-06-25
    Presentation of work at congresses

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  • A simplified radar-based EWS for urban flood warning

     Llort Pavon, Xavier; Sánchez-Diezma Guijarro, Rafael; Rodríguez, Álvaro; Ferrer Sumsi, Miquel; Berenguer Ferrer, Marc; Sempere Torres, Daniel
    European Conference on Radar in Meteorology and Hydrology
    Presentation's date: 2012-06-27
    Presentation of work at congresses

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  • Towards wind farms and meteorological radar coexistence: guidelines for mitigating impacts and examples of operational corrections

     Sempere Torres, Daniel; Berenguer Ferrer, Marc; Pattazzi, Alberto; Salsón, Santiago
    European Conference on Radar in Meteorology and Hydrology
    Presentation's date: 2012-06-28
    Presentation of work at congresses

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  • An approach to the use of NWP forecasts to improve an ensemble nowcasting technique

     Berenguer Ferrer, Marc; Sempere Torres, Daniel
    European Conference on Radar in Meteorology and Hydrology
    Presentation's date: 2012-06-27
    Presentation of work at congresses

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  • HAREN: Hazard Assessment Based on Rainfall European Nowcasts

     Sempere Torres, Daniel; Berenguer Ferrer, Marc; Koistinen, Jarmo; Hohti, Harri; Meyer, Vera
    WMO/WWRP International Symposium on Nowcasting and Very Short Range Forecasting
    Presentation's date: 2012-08-09
    Presentation of work at congresses

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  • Benefits and limitations of using the weather radar for the definition of rainfall thresholds for debris flows. Case study from Catalonia (Spain).

     Abanco Martinez de Arenzana, Claudia; Hürlimann Ziegler, Marcel; Sempere Torres, Daniel; Berenguer Ferrer, Marc
    European Geosciences Union General Assembly
    Presentation of work at congresses

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  • Dam and basin management through an integrated platform

     Llort Pavon, Xavier; Sánchez-Diezma Guijarro, Rafael; Sancho, David; Ferrer Sumsi, Miquel; Hernández, Olver; Berenguer Ferrer, Marc; Sempere Torres, Daniel
    European Conference on Radar in Meteorology and Hydrology
    Presentation's date: 2012-06-27
    Presentation of work at congresses

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  • 3D Radar reflectivity mosaics based on a variational method

     Roca Sancho, Jordi; Berenguer Ferrer, Marc; Sempere Torres, Daniel
    European Conference on Radar in Meteorology and Hydrology
    Presentation's date: 2012-06-25
    Presentation of work at congresses

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  • Hazard Assessment based on Rainfall European Nowcasts

     Berenguer Ferrer, Marc; Sempere Torres, Daniel
    Participation in a competitive project

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  • SBMcast - An ensemble nowcasting technique to assess the uncertainty in rainfall forecasts by Lagrangian extrapolation

     Berenguer Ferrer, Marc; Sempere Torres, Daniel; Pegram, Geoff
    Journal of hydrology
    Date of publication: 2011-07-11
    Journal article

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    Deterministic nowcasting based on Lagrangian extrapolation of recent radar observations is a technique used in many operational and research centers and has proven to be useful at extending the anticipation with which flows can be forecasted with a rainfall–runoff model. However, the improvement in flow forecasts is not known a priory and case-dependent, mostly depending on the predictability of the rainfall field. In this work a probabilistic technique has been developed to automatically quantify the uncertainty in radar-based nowcasts obtained by Lagrangian extrapolation to be used in hydrology. The technique follows the ensemble approach: it generates a number of realizations of rainfall forecasts compatible with observations and that reserve the space and time structure of the rainfall field according to the String of Beads model. The results show that the technique reasonably reproduces the evolution of the rainfall field, but that, overall, the errors are underestimated in part due to the fact that the uncertainty in rainfall forecasts due to errors in the motion field is neglected in this current version of the method.

  • Implications of radar rainfall estimates uncertainty on distributed hydrological model predictions

     Schröter, Michael; Llort Pavon, Xavier; Velasco Forero, Carles; Ostrowski, M.; Sempere Torres, Daniel
    Atmospheric research
    Date of publication: 2011-05
    Journal article

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    Geostatistical radar-raingauge combination with nonparametric correlograms: methodological considerations and application in Switzerland  Open access

     Schiemann, Reinhard; Erdin, Rebecca; Willi, Marco; Frei, Christoph; Berenguer Ferrer, Marc; Sempere Torres, Daniel
    Hydrology and Earth system sciences
    Date of publication: 2011-05-19
    Journal article

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    Modelling spatial covariance is an essential part of all geostatistical methods. Traditionally, parametric semivariogram models are fit from available data. More recently, it has been suggested to use nonparametric correlograms obtained from spatially complete data fields. Here, both estimation techniques are compared. Nonparametric correlograms are shown to have a substantial negative bias. Nonetheless, when combined with the sample variance of the spatial field under consideration, they yield an estimate of the semivariogram that is unbiased for small lag distances. This justifies the use of this estimation technique in geostatistical applications. Various formulations of geostatistical combination (Kriging) methods are used here for the construction of hourly precipitation grids for Switzerland based on data from a sparse realtime network of raingauges and from a spatially complete radar composite. Two variants of Ordinary Kriging (OK) are used to interpolate the sparse gauge observations. In both OK variants, the radar data are only used to determine the semivariogram model. One variant relies on a traditional parametric semivariogram estimate, whereas the other variant uses the nonparametric correlogram. The variants are tested for three cases and the impact of the semivariogram model on the Kriging prediction is illustrated. For the three test cases, the method using nonparametric correlograms performs equally well or better than the traditional method, and at the same time offers great practical advantages. Furthermore, two variants of Kriging with external drift (KED) are tested, both of which use the radar data to estimate nonparametric correlograms, and as the external drift variable. The first KED variant has been used previously for geostatistical radar-raingauge merging in Catalonia (Spain). The second variant is newly proposed here and is an extension of the first. Both variants are evaluated for the three test cases as well as an extended evaluation period. It is found that both methods yield merged fields of better quality than the original radar field or fields obtained by OK of gauge data. The newly suggested KED formulation is shown to be beneficial, in particular in mountainous regions where the quality of the Swiss radar composite is comparatively low. An analysis of the Kriging variances shows that none of the methods tested here provides a satisfactory uncertainty estimate. A suitable variable transformation is expected to improve this.

  • Radar rainfall: separating signal and noise fields to generate meaningful ensembles

     Pegram, Geoff; Llort Pavon, Xavier; Sempere Torres, Daniel
    Atmospheric research
    Date of publication: 2011-05
    Journal article

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    For the purpose of generating meaningful stochastic ensembles of radar estimates of rainfall, a relatively simple and objective method of separating a radar rainfall image into signal and noise is described. An alternative noise field, with the same spectrum as the original noise, can then be simulated and combined with the signal field of each successive image, to generate an ensemble member for performing sensitivity studies. The method is based on identifying the appropriate wavelength in the power spectrum which defines the variance threshold used to separate noise from signal. The algorithm is explained and figures illustrate the efficacy of the procedure.

  • Assessment of future scenarios of climate and land-use changes in the IMPRINTS test-bed areas

     Cabello, A.; Velasco, M.; Barredo, J.I.; Hurkmans, R.T.W.L.; Barrera Escoda, A.; Sempere Torres, Daniel; Velasco Montes, David
    Environmental science and policy
    Date of publication: 2011-11
    Journal article

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  • Geostatistical radar-raingauge combination with nonparametric correlograms: methodological considerations and application in Switzerland

     Schiemann, Reinhard; Erdin, Rebekka; Willi, Marco; Frei, Christoph; Berenguer Ferrer, Marc; Sempere Torres, Daniel
    Geophysical research abstracts
    Date of publication: 2011
    Journal article

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  • Estudio de la incertidumbre asociada a la simulación hidrológica

     Quintero Duque, Felipe
    Defense's date: 2011-03-31
    Department of Geotechnical Engineering and Geo-Sciences, Universitat Politècnica de Catalunya
    Theses

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  • Blending of radar and gauge rainfall measurements: a preliminary analysis of the impact of radar errors

     Sempere Torres, Daniel; Berenguer Ferrer, Marc; Velasco Forero, Carles
    International Symposium on Weather Radar and Hydrology
    Presentation's date: 2011-04
    Presentation of work at congresses

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    Several methodologies have been proposed to combine radar and raingauge measurements with the aim of generating improved quantitative precipitation estimates (QPEs). These methods are based on interpolating point raingauge measurements (implicitly assumed to be "the truth") and benefiting from the structure of the rainfall field as depicted by the radar. The use of a non-parametric approach based on radar measurements has been recently demonstrated, showing the benefits in the interpolation of raingauge measurements under the hypotheses of the Kriging approach. Several experiments have been carried out over a large number of cases and a variety of regions, Kriging with an external drift (i.e. the radar description of the rainfall field) being the approach showing more robust and (overall) better performance. Here, the impact of the discrepancies between two almost-collocated radars on the blended QPE fields was investigated.

    Several methodologies have been proposed to combine radar and raingauge measurements with the aim of generating improved quantitative precipitation estimates (QPEs). These methods are based on interpolating point raingauge measurements (implicitly assumed to be “the truth”) and benefiting from the structure of the rainfall field as depicted by the radar. The use of a non-parametric approach based on radar measurements has been recently demonstrated, showing the benefits in the interpolation of raingauge measurements under the hypotheses of the Kriging approach. Several experiments have been carried out over a large number of cases and a variety of regions, Kriging with an external drift (i.e. the radar description of the rainfall field) being the approach showing more robust and (overall) better performance. Here, the impact of the discrepancies between two almost-collocated radars on the blended QPE fields was investigated.

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    A variational approach to retrieve 3D radar reflectivity composites  Open access

     Roca Sancho, Jordi; Berenguer Ferrer, Marc; Sempere Torres, Daniel
    Conference on Radar Meteorology
    Presentation's date: 2011-09-29
    Presentation of work at congresses

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    This study proposes an alternative methodology to obtain high-resolution radar reflectivity composites based on a variational approach considering different error sources in an explicit manner. The methodology retrieves the 3-dimensional precipitation field most compatible with the observations from the different radars of the network. With this aim, the methodology uses a model that simulates the radar sampling of the atmosphere. The model settings are different for each radar and include features such as the radar location, hardware parameters (beam width, pulse length…) and the scan strategy. The methodology follows the concept of an inverse method based on the minimization of a cost function that penalizes discrepancies between the simulated and actual observations for each radar. The simulation model is able to reproduce the effect of beam broadening with the distance and attenuation by intense precipitation. The methodology has been applied on two radars close to Barcelona (Spain).

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    A radar-based flash flood forecasting for the Llobregat river basin in the Catalonia region (Spain)  Open access

     Quintero Duque, Felipe; Versini, Pierre-Antoine; Baltas, Evangelos; Berenguer Ferrer, Marc; Sempere Torres, Daniel
    Conference on Radar Meteorology
    Presentation's date: 2011-10-28
    Presentation of work at congresses

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    In this research paper, a flash flood modeling system implemented in a Mediterranean river basin is presented. Radar precipitation estimation along with hydrological modeling techniques are implemented within the system for simulating the runoff generation and routing processes occurring in the catchment. However, there exists an uncertainty related with the estimation of radar precipitation (Zawadzki, 1984) and from model calibration (Beven, 2006). Such uncertainty is propagated to the resulting discharge simulations. The aim of this research paper is to propose a methodology to analyze the propagation of uncertainty occurring at the different processes of the modeling system. For this purpose, a Monte Carlo simulation approach is used to consider the uncertainty arising from rainfall and model parameter estimation.

  • Hacia el uso cuantitativo de un mini-radar para zonas urbanas: el proyecto Rainscanner@BCN

     Sempere Torres, Daniel; Park, Shinju; Berenguer Ferrer, Marc; Pfeifer, Monika
    Jornades de Meteorologia Eduard Fontseré
    Presentation's date: 2011-11
    Presentation of work at congresses

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  • Runoff forecasting under errors in quantitative radar rainfall inputs

     Berenguer Ferrer, Marc; Sempere Torres, Daniel
    World Environmental and Water Resources Congress
    Presentation's date: 2011-05-25
    Presentation of work at congresses

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  • Hydrological impact of SBMcast nowcasting ensembles

     Berenguer Ferrer, Marc; Sempere Torres, Daniel
    Conference on Radar Meteorology
    Presentation's date: 2011-10-28
    Presentation of work at congresses

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  • Hydrometeorological value of X-band radar RAINSCANNER® observations

     Park, Shinju; Berenguer Ferrer, Marc; Sempere Torres, Daniel; Llort Pavon, Xavier; Didszun, Jens; Pfeifer, Monika
    Conference on Radar Meteorology
    Presentation's date: 2011-10-27
    Presentation of work at congresses

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  • Desarrollo de una metodología para el uso de entradas de lluvia probabilísticas en sistemas de alerta hidrológica

     Sempere Torres, Daniel; Roca Sancho, Jordi; Berenguer Ferrer, Marc
    Participation in a competitive project

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