Rain cells shape and orientation distribution in south-west of France

Féral, Laurent; Mesnard, Frédéric; Sauvageot, Henri; Castanets, L; Lemorton, J.

doi:10.1016/s1464-1909(00)00155-6

Cited by 34 publications

(37 citation statements)

References 7 publications

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“…Figure 2 shows the distribution of estimated θ 0rad orientation and ellipticity e rad , defined as the ratio e rad =b rad /a rad . Our analysis confirms the results obtained by Von Hardenberg et al (2003) and Féral et al (2000), showing a uniform distribution of raincell orientations and a mean ellipticity of about 0.5 (0.48 in this analysis).…”

Section: Horizontal Profile Estimation From Radar Datasupporting

confidence: 92%

Spatial characterization of raincell horizontal profiles from C-band radar measurements at mid-latitude

et al. 2006

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Abstract.A spatial characterization of mid-latitude mesoscale rain fields from C-band radar measurements is performed by means of a systematic analysis and modelling of convective raincell shapes. To this aim a large rainfall dataset, derived from an operational C-band dualpolarized radar, has been continuously collected from 1996 to 1999. The radar-derived rain fields consist of 1558 grids of 256×256 km 2 with a spatial resolution of 1 km. A new accurate and adaptive algorithm for raincell identification is introduced and thoroughly discussed. From this analysis, a quality-controlled set of 2601 raincells, together with the radial rain intensities (or raincell horizontal profiles), is extracted. Three one-dimensional analytical models of rainfall horizontal profile are reviewed and tested by best fitting their parameters against estimated raincell data. The statistical results of this intercomparison are quantitatively analyzed and discussed in terms of mean rainfall horizontal profiles and root mean square errors.

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Section: Horizontal Profile Estimation From Radar Datasupporting

confidence: 92%

Spatial characterization of raincell horizontal profiles from C-band radar measurements at mid-latitude

et al. 2006

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“…[12] Pawlina and Binaghi [1995] and Féral et al [2000] questioned the validity of this approach and proposed to describe the rain cell shape by its equivalent ellipse, whose parameters are the major axis, the minor axis, and the orientation angle. Whatever the threshold, the results show that the rain cell orientation distribution is uniform while the distribution of the rain cell ellipticity, defined as the ratio of the minor to major axis, indicates that the majority of the small cells are twice longer than wide.…”

Section: Rain Cell Definitionmentioning

confidence: 99%

“…Each cell is approximated by its equivalent ellipse whose geometrical features -major axis length, minor axis length and orientation angle -are computed, by minimization of the moments of inertia [Féral et al, 2000], to finally obtain the cell ellipticity e r .…”

Section: Rain Cell Identificationmentioning

confidence: 99%

HYCELL—A new hybrid model of the rain horizontal distribution for propagation studies: 1. Modeling of the rain cell

et al. 2003

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[1] From radar observations of rain fields at midlatitudes, a new physical model of rain cells is proposed. It strives to describe optimally the rain rate horizontal distribution within rain cells down to 1 mm h À1 . The approach is similar to that of the well-known EXCELL model. The mathematical definition of the model lies in the combination of a gaussian function and an exponential one, the cells having an elliptic horizontal cross section. Due to its hybrid structure, the new model has been named HYCELL. From a conceptual point of view, the gaussian component describes the convective-like high rain rate core of the cell, while the exponential component accounts for the surrounding stratiform-like low rain rate spreading down to 1 mm h À1 . The modeling of a rain cell with HYCELL then requires the determination of seven parameters. The latter is obtained, cell by cell, by solving a set of five fit-forcing equations completed by two continuity equations. The fit-forcing equations involve radar parameters of integral nature which refer not only to the rain cell geometry (area, ellipticity) but also to the rain rate R distribution inside the cell (mean and root mean square values of R and gradient of R). Their analytical expressions are derived from the model definition, while their values are forced to be those derived from radar measurements. Using this method, thousands of rain cells identified from radar observations in the regions of Bordeaux (southwestern France) and Karlsruhe (southwestern Germany) have been modeled. Though both sites are at midlatitude, the climatic contexts differ: oceanic for Bordeaux and continental for Karlsruhe. Results of rain rate horizontal distribution modeling within cells using HYCELL and EXCELL are compared. It is then suggested that the HYCELL model is a new tool which deserves to be considered by system designers to compute propagation parameters.

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“…The spatial distribution of rainfall in convective environments is often examined by focusing on the properties of the convective rain cells (abbreviated hereafter as rain cells), which can be directly derived by exploiting the full threedimensional structure of the cells (Dixon and Wiener, 1993;Johnson et al, 1998;Steiner et al, 1995) or, more commonly, extracting the convective two-dimensional segments from radar data (Barnolas et al, 2010;Cox and Isham, 1988;Féral et al, 2000;von Hardenberg, 2003;Karklinsky and Morin, 2006;Northrop, 1997). A widely used approach requiring only two-dimensional information is to define them as areas in which the rain intensity exceeds a certain threshold.…”

Section: Introductionmentioning

confidence: 99%

Convective rainfall in a dry climate: relations with synoptic systems and flash-flood generation in the Dead Sea region

Belachsen

Marra

Peleg

et al. 2017

Hydrol. Earth Syst. Sci.

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Abstract. Spatiotemporal patterns of rainfall are important characteristics that influence runoff generation and flashflood magnitude and require high-resolution measurements to be adequately represented. This need is further emphasized in arid climates, where rainfall is scarce and highly variable. In this study, 24 years of corrected and gaugeadjusted radar rainfall estimates are used to (i) identify the spatial structure and dynamics of convective rain cells in a dry climate region in the Eastern Mediterranean, (ii) to determine their climatology, and (iii) to understand their relation with the governing synoptic systems and with flashflood generation. Rain cells are extracted using a segmentation method and a tracking algorithm, and are clustered into three synoptic patterns according to atmospheric variables from the ERA-Interim reanalysis. On average, the cells are about 90 km 2 in size, move 13 m s −1 from west to east, and live for 18 min. The Cyprus low accounts for 30 % of the events, the low to the east of the study region for 44 %, and the Active Red Sea Trough for 26 %. The Active Red Sea Trough produces shorter rain events composed of rain cells with higher rain intensities, longer lifetime, smaller area, and lower velocities. The area of rain cells is positively correlated with topographic height. The number of cells is negatively correlated with the distance from the shoreline. Rain-cell intensity is negatively correlated with mean annual precipitation. Flash-flood-related events are dominated by rain cells of large size, low velocity, and long lifetime that move downstream with the main axis of the catchments. These results can be further used for stochastic simulations of convective rain storms and serve as input for hydrological models and for flash-flood nowcasting systems.

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Rain cells shape and orientation distribution in south-west of France

Cited by 34 publications

References 7 publications

Spatial characterization of raincell horizontal profiles from C-band radar measurements at mid-latitude

Spatial characterization of raincell horizontal profiles from C-band radar measurements at mid-latitude

HYCELL—A new hybrid model of the rain horizontal distribution for propagation studies: 1. Modeling of the rain cell

Convective rainfall in a dry climate: relations with synoptic systems and flash-flood generation in the Dead Sea region

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