Scientists at the Hebrew University of Jerusalem have demonstrated that sea spray over the oceans contributes to cleansing air that has been polluted overland. The air pollution is washed down by rain, which occurs because the rain-suppressing effect of such pollution is significantly neutralized. An article on this research appears in the online magazine Science Express, published today.

In previous studies, Prof. Daniel Rosenfeld of the Ring Department of Atmospheric Sciences, and colleagues from the Hebrew University and elsewhere have shown that particles generated by such elements as urban pollution, desert dust and burning of vegetation hinder precipitation by creating nuclei in clouds around which droplets are formed. These droplets are too small to bond together to form actual raindrops, thereby reducing rainfall.

The new observations by Prof. Rosenfeld, together with Hebrew University Ph.D. student Ronen Lahav, Prof. Alexander Khain and Dr. Mark Pinsky, show that precipitation from similar polluted clouds over the ocean is much less affected, because large sea salt nuclei seed the clouds and override the precipitation-suppression effect of the pollution nuclei. Raindrops initiated by the sea salt grow by collecting small cloud droplets that form on the pollution particles, thereby cleansing the air and increasing rainfall prospects.

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Contact: Jerry Barach, msbarach@mscc.huji.ac.il, 972-2-588-2904, Hebrew University of Jerusalem

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