The ability to create clouds and possibly rain is now in the hands of humankind. Recently, in a collaborative geo-engineering project between Swiss, German, and French researchers, small clouds were created by firing a laser into the sky above Berlin, Germany.
The laser strips electrons from atoms in the atmosphere, forming hydroxyl radicals that create sulfur and nitrogen dioxides. These dioxides act as seed’ particles for moisture droplets to form. Current cloud-making techniques involve spreading silver iodide crystals in the atmosphere as the "seeds".
The researchers tried out the system in the lab, creating mini-cloud streams in water-saturated air at -24°C (-11.2F), with visible linear clouds along the path of the laser. Later, during outside testing, the laser was focused at a 60m (197ft.) altitude and produced increased water vapor but no clearly visible clouds.
The laser generates a 220-millijoule pulse for 60 femtoseconds (60 millionth of one billionth of a second). It all sounds pretty tiny but the power is equivalent to 3.5 teraWatts peak power) at a central wavelength of 800 nanometres, a repetition rate of 10Hz and a 4cm (1.6”) beam diameter. Although not ideal, laser cloud makingcould still be better for the planet than flying aircraft or firing rockets into the atmosphere and spraying silver iodideover large areas.