Aircraft flying through clouds can cause condensation to form, resulting in more rain and snow in the skies above airports, according to a new study. According to the results of an investigation published in the journal, Science, reported by AP and Official Wire, the correct conditions for this inadvertent weather modification occur about 5% of the time, rising to 10-15% of the time in colder conditions.
Research by Andrew J. Heymsfield of the US National Center for Atmospheric Research in Colorado, was investigating holes or ‘canals’ that are sometimes seen drilled in clouds after an aircraft has passed through. Studying six commercial airports, the team found that increased snow and rainfall occurs in areas where the unusual cloud holes appear, usually within 60 miles (97km) of the airport. The added rain or snowfall occurred when conditions in the clouds were super-cooled, or comprised of water droplets that were colder than freezing, but which had not yet frozen.
When an aircraft passes through one of these clouds the movement of air over the wings causes a sudden cooling of the air, sometimes down to the critical point where the droplets freeze. They can then fall to earth as snow or rain, depending on whether or not the air is warm enough to melt them on the way down.
Kenneth Sassen, of the University of Alaska Fairbanks, was reported saying that new findings add detail to an already recognised phenomenon. He added however, that the necessary atmospheric conditions were unlikely to be prevalent in more than a handful of airports. Airports studied by Heymsfield’s team were London Heathrow, Frankfurt, Paris Charles De Gaulle, Seattle-Tacoma, Chicago O’Hare and Yellowknife, Northwest Territories, Canada; plus Byrd Station in Antarctica.