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Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/hess-2017-235
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
02 May 2017
Review status
This discussion paper is a preprint. A revision of the manuscript was accepted for the journal Hydrology and Earth System Sciences (HESS).
Convective rainfall in dry climate: relations with synoptic systems and flash-flood generation in the Dead Sea region
Idit Belachsen1,2, Francesco Marra2, Nadav Peleg3, and Efrat Morin2 1Hydrology and Water Resources Program, Hebrew University of Jerusalem, Jerusalem, 91904, Israel
2Institute of Earth Sciences, Hebrew University of Jerusalem, Jerusalem, 91904, Israel
3Institute of Environmental Engineering, Hydrology and Water Resources Management, ETH Zurich, Zurich, Switzerland
Abstract. Space-time patterns of rainfall are important characteristics that influence runoff generation and flash-flood 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 gauge-adjusted radar rainfall estimates are used to identify spatial structure and dynamics of convective rain cells in a dry climate region in the Eastern Mediterranean, to determine their climatology, and to understand their relation with the governing synoptic systems and with flash-flood 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 ERA-Interim reanalyses. On average, they are 90 km2 in size, move 13 m s−1 from west to east, and live 18 minutes. Cyprus low accounts for 30 % of the events, low to the east of the study region for 44 % and Active Red Sea Trough for 26 %. 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.

Citation: Belachsen, I., Marra, F., Peleg, N., and Morin, E.: Convective rainfall in dry climate: relations with synoptic systems and flash-flood generation in the Dead Sea region, Hydrol. Earth Syst. Sci. Discuss., https://doi.org/10.5194/hess-2017-235, in review, 2017.
Idit Belachsen et al.
Idit Belachsen et al.
Idit Belachsen et al.

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Short summary
Space-time rainfall patterns in arid environments are not well known. We derived properties of convective rain cells over the arid Dead Sea region from a long-term radar archive. We found differences in cells properties between synoptic systems and between flash-flood and non-flash-flood events. Large flash-floods are associated with slow rain cells, directed downstream with the main catchment axis. Results from this work can be used for hydrological models and stochastic storm simulations.
Space-time rainfall patterns in arid environments are not well known. We derived properties of...
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