2DVD Data Revisited: Multifractal Insights into Cuts of the Spatiotemporal Rainfall Process

Abstract

International audienceData collected during four heavy rainfall events that occurred in Ardeche (France) with the help of a 2D video disdrometer (2DVD) are used to investigate the structure of the raindrop distribution in both space and time. A first type of analysis is based on the reconstruction of 36-m-height vertical rainfall columns above the measuring device. This reconstruction is obtained with the help of a ballistic hypothesis applied to 1-ms time step series. The corresponding snapshots are analyzed with the help of universal multifractals. For comparison, a similar analysis is performed on the time series with 1-ms time steps, as well as on time series of accumulation maps of N consecutive recorded drops (therefore with variable time steps). It turns out that the drop distribution exhibits a good scaling behavior in the range 0.5-36 m during the heaviest portion of the events, confirming the lack of empirical evidence of the widely used homogenous assumption for drop distribution. For smaller scales, drop positions seem to be homogeneously distributed. The notion of multifractal singularity is well illustrated by the very high-resolution time series

Drop by drop backscattered signal of a 50 × 50 × 50 m3 volume: A numerical experiment

“…Before discussing the results, it should be mentioned that there is no data available at drop scale on such a large volume to properly validate the model developed here, which by the way is also the case for more homogeneous models commonly used in other works. Nevertheless it is in agreement with some prior results (based on imperfect data, Gires et al 2015, Lilley et al 2006 hinting at scaling properties down to 0.5 m. Further investigations involving both instrumentations and modelling developments will be needed to improve it as well as to validate it.…”

“…3. They correspond to the ones obtained with the help of a 2D-video disdrometer for two different minutes of an event studied in Gires et al (2015).…”

“…fields (Lilley et al 2006;Gires et al 2015) for which C 1 and α estimates are respectively in the lower and upper bound of the interval studied here. In this paper we keep the wider range of observed parameters to test in a more general way the influence of UM parameters.…”

Overview towards improved understanding of the mechanisms leading to heavy precipitation in the Western Mediterranean: lessons learned from HyMeX

“…Among them, a large number of available disdrometers and MRRs were used to improve the quality of observations (Raupach andBerne, 2016 andAdirosi et al, 2016) and the characterization of the raindrop's PSD (Adirosi et al, 2014, Adirosi et al, 2015, Schleiss and Smith, 2015, including its very small-scale variability (Gires et al, 2015).…”

On the Optimal Measuring Area for Pointwise Rainfall Estimation: A Dedicated Experiment with 14 Laser Disdrometers

“…This kind of instrument has been proved crucial for several aspects of hydrological science. Thus, disdrometers have been employed to analyze the microstructure of rain events (Jameson et al 2016;Ignaccolo et al 2009), including its spatiotemporal structure in 3D (Gires et al 2015); characterize the PSD in flood events (Friedrich et al 2016); delineate flood areas (Beauchamp et al 2015); assist radars to estimate the spatial correlation of the PSD (Bringi et al 2015;Thurai et al 2012); develop new algorithms (Anagnostou et al 2013); verify quantitative precipitation estimates from weather radars (Bringi et al 2011;Gourley et al 2009); perform hydrological validation of nowcastings (Berenguer et al 2005); study radio signal propagation (Montopoli et al 2008;Watson and Hodges 2009); and carry out error analysis at catchment scale (Jordan et al 2003).…”