Space-time simulation of intermittent rainfall with prescribed advection field: Adaptation of the turning band method

Space-time rainfall simulation is useful to study questions like, for instance, the propagation of rainfall-measurement uncertainty in hydrological modeling. This study adapts a classical Gaussian field simulation technique, the turning-band method, in order to produce sequences of rainfall fields satisfying three key features of actual precipitation systems: (i) the skewed point distribution and the space-time structure of nonzero rainfall (NZR); (ii) the average probability and the space-time structure of intermittency; and (iii) a prescribed advection field. The acronym of our simulator is SAMPO, for simulation of advected mesoscale precipitations and their occurrence. SAMPO assembles various theoretical developments available from the literature. The concept of backtrajectories introduces a priori any type of advection field in the heart of the turning band method (TBM). TBM outputs transformation into rainfall fields with a desired structure is controlled using Chebyshev-Hermite polynomial expansion. The intermittency taken as a binary process statistically independent of the NZR process allows the use of a common algorithm for both processes. The 3-D simulation with a space-time anisotropy captures important details of the precipitation kinematics summarized by the Taylor velocity of both NZR and intermittency. A case study based on high-resolution weather radar data serves as an example of model inference. Illustrative simulations revisit some classical questions about rainfall variography like the influence of advection or intermittency. They also show the combined role of Taylor’s and advection velocities

Comprendre la production et la régulation des conflits environnementaux pour caractériser une trajectoire de sécurisation du risque. Le cas de la plaine de Grenoble face aux inondations (1219 - 1778)

International audienceThis paper deals with the historical evolution of flood prevention institutions in the plain surrounding Grenoble, from 1219 to 1789. Based on an analysis of the existing scientific literature, we map the evolving relationship between the inhabitants and the public authorities to cope with flooding. For this purpose, we use the notion of hydro-social contract. We elaborate a grid based on historical institutionalism in order to examine the quality of the institutions coping with flood risk over time. Meanwhile we follow a critical approach in the sense that we look at flooding as an indicator of environmental inequalities. Our results enable the identification of three periods of time, each with its own way of providing the population with flood protection. We show a gradual transfer of responsibility for flood intervention, which moved from the feudal communities through to the city of Grenoble and finally to the central State. In terms of institutional arrangements, we highlight the changing structure of these institutions over time and also across the cognitive, normative and regulative stages. This paper presents finally the advent of a complex institutional regime that resulted in major freedom limitations to both the population and the rivers.Este artículo hace el trazado de la evolución histórica de las instituciones de protección contra las inundaciones en la planicie de Grenoble de 1219 a 1778. Apoyándonos en la noción de contrato hidro-social (Novalia et al., 2009; Dill & Pelling, 2010), nos proponemos modelizar la relación evolutiva que mantienen los habitantes con el poder público con relación al problema de las inundaciones. Desplegando un procedimiento fundado sobre el insitucionalismo histórico (Cleaver, 2015) nuestros resultados identifican tres configuraciones institucionales o « procedimientos regulatorios » distintos, que reflejan tres maneras de asegurar la protección contra las inundaciones. En términos de actores movilizados, ponemos también en evidencia una transferencia progresiva de las misiones de protección contra las inundaciones desde las comunidades de habitantes primero en dirección de la ciudad de Grenoble y depues hacia el Estado. El segundo hecho estilizado relativo a la naturaleza de las conexiones institucionales especificadas históricamente da testimonio de una evolución progresiva de su estructuración: formulamos la hipótesis de que esta última se apoya sucesivamente, en un periodo dado y de manera prioritaria, sobre uno de los « pilares » institucionales (cognitivo, normativo y reglamentario) introducidos por Scott (1995). Nosotros mostramos finalmente que la naturaleza de los dispositivos especificados revelan su nivel de coherencia y de robustez, y que su evolución puede comprenderse, además de otros factores explicativos, en coherencia con la exacerbación o la calma de los conflictos y de las desigualdades que ellos generan.Cet article retrace l’évolution historique des institutions de protection contre les inondations dans la plaine de Grenoble, de 1219 à 1778. En nous appuyant sur la notion de contrat hydro-social (Novalia et al., 2009 ; Dill & Pelling, 2010), nous proposons de modéliser le rapport évolutif qu’entretiennent les habitants à la puissance publique relativement à la question des inondations. Déployant une démarche fondée sur l’institutionnalisme historique critique (Cleaver & Koenig, 2015), nos résultats dégagent trois configurations institutionnelles ou « agencements régulatoires » distincts, reflétant trois manières d’assurer la protection contre les inondations. En termes d’acteurs mobilisés, nous mettons ainsi en évidence un transfert progressif des missions de protection contre les inondations des communautés habitantes en direction de la ville de Grenoble puis de l’État. Le deuxième fait stylisé, relatif à la nature des assemblages institutionnels spécifiés historiquement, témoigne d’une évolution progressive de leur structuration : nous formulons l’hypothèse que cette dernière s’appuie successivement, à une période donnée et de manière prioritaire, sur l’un des « piliers » institutionnels (cognitif, normatif et réglementaire) introduits par Scott (1995). Nous montrons enfin que la nature des agencements spécifiés révèle leur niveau de cohérence et de robustesse, et que leur évolution peut se comprendre, parmi d’autres facteurs explicatifs, à l’aune de l’exacerbation ou du reflux des conflits et des inégalités qu’ils génèrent

Variographie des cumuls pluviométriques en présence d'une advection

International audienceThis study provides a coherent theoretical framework between the field structures of rainfall accumulations over different durations. Following a classical geostatistical approach, we assume the existence of an elemental space–time stationary rainfall process and we consider rainfall accumulation as a regularization of this elemental process over time supports of various sizes. The corresponding space–time elemental variogram is used to derive the spatial and temporal variograms of accumulated values. In addition to an elemental variance, the framework incorporates both the anisotropy between time and space variability (Taylor velocity) and a constant advection of the rain fields. The proposed formulation verifies empirical observations made in past variographic studies like an increasing spatial range and a decreasing sill with increasing accumulation times. It provides new insights about the respective influence of accumulation and advection on the variogram shape and, as a side product, about Eulerian and Lagrangian properties of rainfall variability. From a set of experimental variograms calculated for different accumulation durations, we use the proposed formulation through a simple optimization algorithm to infer a four-parameter model characterizing the elemental rainfall process and the advection. A network of 21 daily rain gauges over the Loire Basin, France, gives an application illustration. We use a set of experimental space and time variograms corresponding to accumulation durations of 1–4 days. The identified parameters provide a fairly good fit of the experimental variogram set and their orders of magnitude look meteorologically sound. The main limitations and further developments of the method are discussed

Précipitations : faire la distinction entre l'hypothèse de Taylor et celle d'un champ figé

International audienceSince the seminal work of Zawadzki in the seventies, the so-called Taylor's "frozen" hypothesis has been regularly used to study the statistical properties of rainfall patterns. This hypothesis yields a drastic simplification in terms of symmetry of the space-time structure-the large-scale advection velocity is the conversion factor used to link the time and space autocorrelation functions (ACFs) of the small-scale variability. This study revisits the frozen hypothesis with a geostatistical model. Using analytical developments and numerical simulations tuned on available case studies from the literature, the role of large- and small-scale rainfall kinematics on the properties of the space-time ACF and associated fluctuations is investigated. In particular, the merits and limits of the ACF signature classically used to test the frozen hypothesis are examined. The conclusion is twofold. Taylor's hypothesis, understood as the quest for a space-time symmetry in rain field variability, remains important in hydrometeorology four decades after the pioneering work of Zawadzki. The frozen hypothesis, introduced for simplification purposes, appears difficult to check and too constraining. The methods proposed to check the hypothesis rely too directly on the use of the advection velocity as a space-time conversion factor instead of contemplating the ACF signature more globally. The model proposed that using two characteristic velocities instead of one appears more flexible to fit the ACF behaviors presented in the literature. This remains to be checked over a long-term high-resolution dataset

Comprendre la production et la régulation des conflits environnementaux pour caractériser une trajectoire de sécurisation du risque. Le cas de la plaine de Grenoble face aux inondations (1219 - 1778)

International audienceThis paper deals with the historical evolution of flood prevention institutions in the plain surrounding Grenoble, from 1219 to 1789. Based on an analysis of the existing scientific literature, we map the evolving relationship between the inhabitants and the public authorities to cope with flooding. For this purpose, we use the notion of hydro-social contract. We elaborate a grid based on historical institutionalism in order to examine the quality of the institutions coping with flood risk over time. Meanwhile we follow a critical approach in the sense that we look at flooding as an indicator of environmental inequalities. Our results enable the identification of three periods of time, each with its own way of providing the population with flood protection. We show a gradual transfer of responsibility for flood intervention, which moved from the feudal communities through to the city of Grenoble and finally to the central State. In terms of institutional arrangements, we highlight the changing structure of these institutions over time and also across the cognitive, normative and regulative stages. This paper presents finally the advent of a complex institutional regime that resulted in major freedom limitations to both the population and the rivers.Este artículo hace el trazado de la evolución histórica de las instituciones de protección contra las inundaciones en la planicie de Grenoble de 1219 a 1778. Apoyándonos en la noción de contrato hidro-social (Novalia et al., 2009; Dill & Pelling, 2010), nos proponemos modelizar la relación evolutiva que mantienen los habitantes con el poder público con relación al problema de las inundaciones. Desplegando un procedimiento fundado sobre el insitucionalismo histórico (Cleaver, 2015) nuestros resultados identifican tres configuraciones institucionales o « procedimientos regulatorios » distintos, que reflejan tres maneras de asegurar la protección contra las inundaciones. En términos de actores movilizados, ponemos también en evidencia una transferencia progresiva de las misiones de protección contra las inundaciones desde las comunidades de habitantes primero en dirección de la ciudad de Grenoble y depues hacia el Estado. El segundo hecho estilizado relativo a la naturaleza de las conexiones institucionales especificadas históricamente da testimonio de una evolución progresiva de su estructuración: formulamos la hipótesis de que esta última se apoya sucesivamente, en un periodo dado y de manera prioritaria, sobre uno de los « pilares » institucionales (cognitivo, normativo y reglamentario) introducidos por Scott (1995). Nosotros mostramos finalmente que la naturaleza de los dispositivos especificados revelan su nivel de coherencia y de robustez, y que su evolución puede comprenderse, además de otros factores explicativos, en coherencia con la exacerbación o la calma de los conflictos y de las desigualdades que ellos generan.Cet article retrace l’évolution historique des institutions de protection contre les inondations dans la plaine de Grenoble, de 1219 à 1778. En nous appuyant sur la notion de contrat hydro-social (Novalia et al., 2009 ; Dill & Pelling, 2010), nous proposons de modéliser le rapport évolutif qu’entretiennent les habitants à la puissance publique relativement à la question des inondations. Déployant une démarche fondée sur l’institutionnalisme historique critique (Cleaver & Koenig, 2015), nos résultats dégagent trois configurations institutionnelles ou « agencements régulatoires » distincts, reflétant trois manières d’assurer la protection contre les inondations. En termes d’acteurs mobilisés, nous mettons ainsi en évidence un transfert progressif des missions de protection contre les inondations des communautés habitantes en direction de la ville de Grenoble puis de l’État. Le deuxième fait stylisé, relatif à la nature des assemblages institutionnels spécifiés historiquement, témoigne d’une évolution progressive de leur structuration : nous formulons l’hypothèse que cette dernière s’appuie successivement, à une période donnée et de manière prioritaire, sur l’un des « piliers » institutionnels (cognitif, normatif et réglementaire) introduits par Scott (1995). Nous montrons enfin que la nature des agencements spécifiés révèle leur niveau de cohérence et de robustesse, et que leur évolution peut se comprendre, parmi d’autres facteurs explicatifs, à l’aune de l’exacerbation ou du reflux des conflits et des inégalités qu’ils génèrent