Modulation of homogeneous space-time rainfall cascades to account for orographic influences

Abstract

Abstract. The development of efficient space-time rainfall downscaling procedures is highly important for the implementation of a meteo-hydrological forecasting chain operating over small watersheds. Multifractal models based on homogeneous cascade have been successfully applied in literature to reproduce space-time rainfall events retrieved over ocean, where the hypothesis of spatial homogeneity can be reasonably accepted. The feasibility to apply this kind of models to rainfall fields occurring over a mountainous region, where spatial homogeneity may not hold, is herein investigated. This issue is examined through the analysis of rainfall data retrieved by the high temporal resolution rain gage network of the Sardinian Hydrological Survey. The proposed procedure involves the introduction of a modulating function which is superimposed to homogeneous and isotropic synthetic fields to take into account the spatial heterogeneity detected in observed precipitation events. Specifically the modulating function, which reproduces the differences in local mean values of the precipitation intensity probability distribution, has been linearly related to the terrain elevation of the analysed spatial domain. Comparisons performed between observed and synthetic data show how the proposed procedure preserves the observed rainfall fields features and how the introduction of the modulating function improves the reproduction of spatial heterogeneity in rainfall probability distributions.

Evaluation of future hydrological cycle under climate change scenarios in a mesoscale Alpine watershed of Italy

“…Therefore, precipitation is held constant with respect to altitude (see e.g. Badas et al, 2006 for an approach to modelling of spatially varying precipitation within random cascades). We convert total precipitation into snow by use of a ground temperature T .…”

A non-stationary stochastic ensemble generator for radar rainfall fields based on the short-space Fourier transform

“…A few approaches have been proposed to adapt the stochastic generators to better capture the local variability of precipitation. Pathirana and Herath (2002) and Badas et al (2006) proposed to filter or remove the heterogeneities of the precipitation field before applying a homogeneous multifractal downscaling technique and re-adding the trend after running the stochastic simulation. A similar strategy was employed in a recent STEPS implementation, which computes the local mean and variance of the rainfall field on a regular grid to remove the local non-stationarity before adding the homogeneous stochastic perturbations (Seed et al, 2013).…”

Distributed hydrologic modeling of a sparsely monitored basin in Sardinia, Italy, through hydrometeorological downscaling

“…1c); (ii) the land cover (LC) map in digital format, derived from the COoRdination de l'INformation sur l'Environnement (CORINE) project of the European Environment Agency (EEA) for the year 2008; (iii) a hard copy of a pedological map of Sardinia at scale 1:250 000 (Aru et al, 1992); and (iv) orthophotos of the entire island for years 1954 and 2006. The LC and soil texture maps were pre-processed to be utilized as model inputs. The original CORINE LC classes were aggregated into 8 groups, obtaining the map shown in Fig.…”

“…The pedological map was digitized and georeferenced resulting in 17 classes in the RMB. For each class of the map, Aru et al (1992) provide a range of soil texture and a qualitative description of soil depths. To reduce the uncertainty on the soil texture classification, a series of field campaigns were conducted in 2011 by the project described in Ludwig et al (2010), during which a total of 50 soil samples of 80 cm depth were collected throughout the watershed and analyzed to characterize the texture.…”