Zapping clouds with lasers could tweak planet’s temperature

Future technology might allow manipulation of ice crystals to alter climate

Mary Matthews, Jean-Pierre Wolf and co-workers investigate the interaction of ultrashort laser filaments with individual 90-μm ice particles, representative of cirrus particles. The ice particles fragment under laser illumination. By monitoring the evolution of the corresponding ice/vapor system at up to 140,000 frames per second over 30 ms, we conclude that a shockwave vaporization supersaturates the neighboring region relative to ice, allowing the nucleation and growth of new ice particles, supported by laser-induced plasma photochemistry. This process constitutes the first direct observation of filament-induced secondary ice multiplication, a process that strongly modifies the particle size distribution and, thus, the albedo of typical cirrus clouds.

The researchers injected water drops into a chilled chamber that mimics the frigid conditions high in the atmosphere, where wispy cirrus clouds live. The water froze into spherical ice particles, which the scientists walloped with short, intense bursts of laser light.When the laser hits an ice particle, ultrahot plasma forms at its center, producing a shock wave that breaks the particle apart and vaporizes much of the ice. The excess water vapor left in the aftermath then condenses and freezes into new, smaller ice particles. Applying this technique to clouds is “a long, long, long way in the future,” says physicist Mary Matthews of the University of Geneva, a coauthor of the study. Current laser technology is not up to the task of cloud zapping — yet. “What we are hoping for is that the advances in laser technology, which are moving faster and faster all the time, will enable high-powered, mobile lasers,” Matthews says. Reference: Matthews, M., F. Pomel, C. Wender, A. Kiselev, D. Duft, J. Kasparian, J.-P. Wolf and T. Leisner (2016). Laser vaporization of cirrus-like ice particles with secondary ice multiplication. Sci. Adv. 2. (10.1126/sciadv.1501912) Matthews-2016 (896 KB).