Ultrashort-pulse lasers as an emerging tool for controlling the weather will be the topic of interest at a gathering of atmospheric physicists, meteorologists and climatologists next month at the World Meteorological Organisation in Geneva. The Helvetera laser platform, a chirped-pulse-amplified laser, is the most powerful ultrashort and ultra-intense laser source in Switzerland. The terawatt laser is used for monitoring pollution in the atmosphere, lightning control and cloud seeding by researchers, including Jean-Pierre Wolf and Jérôme Kasparian of the University of Geneva, who are co-chairing a conference in Geneva next month on using lasers to control weather. Courtesy of University of Geneva Biophotonics Group. The Conference on Lasers, Weather and Climate (LWC 2013, Sept. 16-18) explores topics such as inducing lightning strikes with lasers, using lasers to seed rain clouds, and the similarities between nonlinear propagation and natural phenomena like rogue waves. The goal, say LWC 2013 co-chairs Jean-Pierre Wolf and Jérôme Kasparian of the University of Geneva, is to build a community dedicated to laser-based weather modulation by facilitating contact between researchers from different communities, such as specialists in atmospheric and laser physics. Wolf leads the Biophotonics Group at the university and Kasparian is a senior researcher. Other conference sponsors are MUST (Molecular Ultrafast Science and Technology), the Swiss National Science Foundation, and the Group on Earth Observations, a voluntary partnership of governments and international organizations. Weather-control research (See: Lab Lightning Strikes Same Place More Than Twice) has “triggered an increasing interest and activity in many groups worldwide,[but] the highly interdisciplinary nature of the subject limited its development due to the need for enhanced contacts between laser and atmospheric physicists, chemists, electrical engineers, meteorologists, and climatologists,” the co-chairs say on the conference’s website. Clouds and their impact on the climate system are the largest source of uncertainty in predicting future climate events, Wolf, Kasparian and colleagues said in a paper published online in June by PNAS. In “Laser-induced plasma cloud interaction and ice multiplication under cirrus cloud conditions,” they report on the interaction of intense light pulses with water and ice clouds observed in a cloud simulator. They discovered that, under typical storm cloud conditions, where ice and supercooled water coexist, the laser-generated plasma has no direct influence on ice formation or precipitation. But in thin, cirrus ice clouds, the laser action induced a “surprisingly strong” effect, building up ice. Rogue wave sequence showing a 60-ft-plus wave hitting a tanker headed south from Valdez, Alaska. The ship was running in about 25-ft seas when a monster wave struck it broadside on the starboard side. A conference in Geneva next month will explore the similarities between nonlinear propagation and natural rogue waves. Courtesy of the National Oceanic and Atmospheric Administration photo library. “Within a few minutes, the laser action led to a strong enhancement of the total ice particle number density in the chamber by up to a factor of 100,” they said in the paper. “This surprising effect might open new perspectives for remote sensing of water vapor and ice in the upper troposphere.” Lightning photo taken by Shane Lear of Orange, Australia, from the roof of his home. A conference in Geneva next month will explore topics such as generating and directing laser-based lightning. Courtesy of the NOAA Photo Library. Wolf and Kasparian also take part in mobile experiments under Teramobile, a French-German collaboration of CNRS in France and DFG in Germany that involves five research institutes. By firing an ultrashort, ultra-intense laser into the sky, they are investigating nonlinear propagation of such femtosecond terawatt laser pulses over long distances in the atmosphere and their application to atmospheric research. The project includes lidar remote sensing of atmospheric pollutants, as well as using a mobile 5-TW laser the size of a shipping container to trigger and channel lightning. Confirmed invited speakers for LWC 2013 are: Gilles Peres, Airbus Alejandro Aceves, Southern Methodist University Günter Steinmeyer, Max-Born Institute, Berlin John Dudley, University of Franche-Comté, Besançon, France Jonathan Reid, Bristol University Ludger Wöste, Freie Universität Berlin See Leang Chin, Laval University, Quebec Thomas Leisner, Universität Heidelberg and Karlsruhe Institute of Technology Takashi Fujii, CRIEPI, Tokyo Aurélien Houard, ENSTA, Palaiseau, France Jean-Claude Diels, University of New Mexico Jean-Claude Kieffer, INRS, Montreal Keitaro Yoshihara, Toyota Research Institute & Tokyo Metropolitan University The conference will be held at the offices of the World Meteorological Organisation. For more information, visit: www.laserweatherandclimate.com