Rainfall in the Levant drylands is scarce but can potentially generate high-magnitude flash floods. Rainstorms are caused by distinct synoptic-scale circulation patterns: Mediterranean cyclone (MC), active Red Sea trough (ARST), and subtropical jet stream (STJ) disturbances, also termed tropical plumes (TPs). The unique spatiotemporal characteristics of rainstorms and floods for each circulation pattern were identified. Meteorological reanalyses, quantitative precipitation estimates from weather radars, hydrological data, and indicators of geomorphic changes from remote sensing imagery were used to characterize the chain of hydrometeorological processes leading to distinct flood patterns in the region. Significant differences in the hydrometeorology of these three flood-producing synoptic systems were identified: MC storms draw moisture from the Mediterranean and generate moderate rainfall in the northern part of the region. ARST and TP storms transfer large amounts of moisture from the south, which is converted to rainfall in the hyperarid southernmost parts of the Levant. ARST rainfall is local and intense, whereas TP rainfall is widespread and prolonged due to high precipitation efficiency and large-scale forcing. Thus, TP rainfall generates high-magnitude floods in the largest catchments; integration of numerous basins leads to sediment feeding from the south into the Dead Sea, exhibited in large sediment plumes. Anecdotal observations of the channel with the largest catchment in the region (Nahal HaArava) indicate that TP floods account for noticeable geomorphic changes in the channel. It provides insights into past intervals of increased flash flood frequency characterized by episodes of marked hydrogeomorphic work; such an increase is especially expected during intervals of southerly situated and southwesterly oriented STJs.
Bibliographical noteFunding Information:
Acknowledgments. This study is a contribution to the PALEX project ‘‘Paleohydrology and Extreme Floods from the Dead Sea ICDP Core,’’ funded by the DFG (Grant BR2208/13-1/-2). It is also partially funded by the Israel Science Foundation (1007/15), the NSF-BSF (BSF 2016953), the Israel Ministry of Science and Technology, and the Advanced School for Environmental Studies at the Hebrew University of Jerusalem, and is a contribution to the HyMeX program. IMS radar and rain gauge data were provided and preprocessed by the Israel Meteorological Service (ims.gov.il). Shacham radar data were provided by EMS-Mekorot projects (emsmekorotprojects. com). Discharge data were provided by the Israeli hydrological service of the Israeli Water Authority. Aerial photographs were provided by the Geological Survey of Israel (gsi.gov.il/eng/). The authors also thank Francesco Marra, Yair Rinat, and Idit Belachsen for fruitful discussions, and Prof. Lisa Ely and an anonymous reviewer for providing helpful comments on the manuscript. The authors have no conflict of interest to declare.
© 2018 American Meteorological Society.
- Extreme events
- Flood events
- Radars/Radar observations
- Synoptic climatology
ASJC Scopus subject areas
- Atmospheric Science