Meso-scale weather systems, such as convective haboobs, are considered to be an important dust generation mechanism. In Israel, however, rather than of meso-scale weather systems, most dust storms are generated by synoptic-scale systems, originating from Sahara and Arabia. Consequently, only distal sources of suspended and deposited dust in Israel are currently reported. Here we report the first detailed study on the merging of synoptic- and meso-scale weather systems leading to a prominent dust outbreak over the Negev, Israel. During the afternoon of May 2nd, 2007, a massive dust storm covered the northern Negev, forming a one kilometer high wall of dust. The haboob was associated with PM10 concentrations of 1000–1500 μg m−3 that advanced at a speed of 10–15 m s−1 and caused temporary closure of local airports. In contrast to most reported haboobs, this one was generated by a sea breeze front acting as a weak cold front enhanced by a cold core cyclone positioned over Libya and Egypt. The sea breeze that brought cold and moist marine air acted as a gravity current with strong surface winds. The sources for the haboob were the loessial soils of the northwestern Negev, especially agricultural fields that were highly disturbed in late spring to early summer. Such surface disturbance is caused by agricultural and/or intensive grazing practices. Our study emphasizes the importance of local dust sources in the Negev and stresses loess recycling as an important process in contemporary dust storms over Israel.
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We thank the personnel of the airports in the Negev who shared their first-hand observations and impressions of the haboob, especially S. Orman for the use of his photos. We thank Maya Bartov, Eitan Maze, Roni Drori, Nadav Lensky, and the Dead Sea Works for providing valuable meteorological data. Thanks to Kerstin Schepanski, Ilan Koren, Hamish McGowan, Amit Mushkin, Ilan Stavi, and Alon Maor for fruitful discussions during different periods of research. We thank Bevi Katz for English editing and two anonymous reviewers for improving the manuscript. This research was supported by the Israel Science Foundation (grant No. 1672/15). This paper is part of the work of the GEODUST (GEOmorphology of DUST sources and dynamics of dust emission from different geomorphic units) international focus group (1617F) of the INQUA Commission on Terrestrial Processes, Deposits, and History (TERPRO).
© 2016 Elsevier B.V.