Université de Neuchâtel

Simulating rainfall time-series : how to account for statistical variability at multiple scales?

Oriani, Fabio ; Mehrotra, R ; Mariéthoz, Grégoire ; Straubhaar, Julien ; Sharma, A ; Renard, Philippe

In: Stochastic Environmental Research and Risk Assessment, 2018, vol. 32, p. 321-340

Daily rainfall is a complex signal exhibiting alternation of dry and wet states, seasonal fluctuations and an irregular behavior at multiple scales that cannot be preserved by stationary stochastic simulation models. In this paper, we try to investigate some of the strategies devoted to preserve these features by comparing two recent algorithms for stochastic rainfall simulation: the first one is...

Université de Neuchâtel

Stochastic simulation of rainfall and climate variables using the direct sampling technique

Oriani, Fabio ; Renard, Philippe (Dir.)

Thèse de doctorat : Université de Neuchâtel, 2015.

An accurate statistical representation of hydrological processes is of paramount importance to evaluate the uncertainty of the present scenario and make reliable predictions in a changing climate. A wealth of historic data has been made available in the last decades, including a consistent amount of remote sensing imagery describing the spatio-temporal nature of climatic and hydrological...

Université de Neuchâtel

Binary upscaling on complex heterogeneities : The role of geometry and connectivity

Oriani, Fabio ; Renard, Philippe

In: Advances in Water Resources, 2014, vol. 64, p. 47-61

The equivalent conductivity (Keq) of a binary medium is known to vary with the proportion of the two phases, but it also depends on the geometry and topology of the inclusions. In this paper, we analyze the role of connectivity and shape of the connected components through a correlation study between Keq and two topological and geometrical indicators: the Euler...

Université de Neuchâtel

Simulation of rainfall time series from different climatic regions using the direct sampling technique

Oriani, Fabio ; Straubhaar, Julien ; Renard, Philippe ; Mariethoz, Grégoire

In: Hydrology and Earth System Sciences, 2014, vol. 18, p. 3015-3031

The direct sampling technique, belonging to the family of multiple-point statistics, is proposed as a nonparametric alternative to the classical autoregressive and Markovchain-based models for daily rainfall time-series simulation. The algorithm makes use of the patterns contained inside the training image (the past rainfall record) to reproduce the complexity of the signal without inferring its...

Université de Neuchâtel

Modeling Fine-Scale Geological Heterogeneity : Examples of Sand Lenses in Tills

Kessler, Timo Christian ; Comunian, Alessandro ; Oriani, Fabio ; Renard, Philippe ; Nilsson, Bertel ; Klint, Knud Erik ; Bjerg, Poul Løgstrup

In: Ground Water, 2013, vol. 51, no. 5, p. 692-705

Sand lenses at various spatial scales are recognized to add heterogeneity to glacial sediments. They have high hydraulic conductivities relative to the surrounding till matrix and may affect the advective transport of water and contaminants in clayey till settings. Sand lenses were investigated on till outcrops producing binary images of geological cross-sections capturing the size, shape and...