Ice Nuclei, Rainwater Chemical Composition, and Static Cloud Seeding Effects in Israel

Yoav Levi Hebrew University of Jerusalem, Jerusalem, Israel

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Daniel Rosenfeld Hebrew University of Jerusalem, Jerusalem, Israel

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Abstract

This study analyzed the temporal and spatial variation of natural ice nuclei (IN), total suspended particles (TSP), and rainwater chemical composition (RCC) in Israel. This research is complementary to the statistical analyses of cloud seeding, which have shown significant positive seeding effects only in northern Israel, together with detrimemtal effects of desert dust.

It was observed that the concentration of continental components dissolved in rainwater increases by about an order of magnitude from northern to southern Israel. High values of IN, TSP, and continental origin matter dissolved in rainwater were coincident with geographic location and synoptic conditions that are indicative of the presence of desert dust. These conditions are coincident with the situations in which cloud seeding did not result in significant rain enhancement.

According to geochemical ratios, a major fraction of the dust found in the rainwater originated at the Sahara Desert. These findings support the hypothesis that desert dust has a detrimental effect on cloud seeding in Israel, due to its cloud condensation nuclei and/or ice nucleating activity.

Abstract

This study analyzed the temporal and spatial variation of natural ice nuclei (IN), total suspended particles (TSP), and rainwater chemical composition (RCC) in Israel. This research is complementary to the statistical analyses of cloud seeding, which have shown significant positive seeding effects only in northern Israel, together with detrimemtal effects of desert dust.

It was observed that the concentration of continental components dissolved in rainwater increases by about an order of magnitude from northern to southern Israel. High values of IN, TSP, and continental origin matter dissolved in rainwater were coincident with geographic location and synoptic conditions that are indicative of the presence of desert dust. These conditions are coincident with the situations in which cloud seeding did not result in significant rain enhancement.

According to geochemical ratios, a major fraction of the dust found in the rainwater originated at the Sahara Desert. These findings support the hypothesis that desert dust has a detrimental effect on cloud seeding in Israel, due to its cloud condensation nuclei and/or ice nucleating activity.

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