Lightning follows ship-tracks in Eastern Mediterranean winter thunderstorms.

The interaction between aerosol particles and thunderstorm evolution and properties is complex and was studied by direct observational campaigns, remote sensing from space and through numerical simulations. Aerosols invigorate convection and can lead to enhanced charging manifested in more lightning, but they can also lead to a "Boomerang Effect" where too large concentrations of particles lead to diminished vertical development and weaker electrical activity. The effects of ship exhaust on ocean cloudiness have been studied intensively in recent years, following the discovery of prolonged ship tracks in oceanic regions where maritime transportation is most heavy, leading to large-scale changes in albedo and reduced precipitation. Recently it was shown that aerosols emitted by ships also tend to increase lightning activity, by modifying the dynamics and microphysics of clouds formed directly above the busiest shipping lanes. We study the effects of ship-emitted aerosols on thunderstorms in one of the busiest shipping routes in the world: the Mediterranean Sea between the Suez Canal and the Gibraltar Straights. This region hosts hundreds of ships daily, and space observations show considerable enhancement of the Aerosol Optical Depth (AOD) and NOx concentrations there, some from land sources and others directly related to ship emissions. The research utilized lightning detection networks' data (ENTLN) and studied the properties of lightning (peak current, multiplicity, polarity) with respect to aerosol concentrations and meteorological conditions. Initial results from the Eastern Mediterranean shows a marked increase in winter (DJF) lightning activity over the main east-west shipping lanes, where a conspicuously larger fraction of superbolts (I > 200 kA) is observed. We suggest that the synergistic action of desert dust and air-pollution aerosols acts to invigorate (and sometimes diminish) convection - depending on their relative concentrations and the ambient meteorological conditions. Results from numerical simulations with the latest version of the WRF-ELEC model with advanced spectral-bin microphysics (SBM) will be presented.