Airplanes Add to Snowfall at Airports
Researching and studying the holes that are made by aircraft in clouds, referred to as canals or hole-punches, has revealed very interesting facts for researchers. A team of researchers concentrated on six airports in particular, including the very busy Seattle-Tacoma International Airport. By looking at the effect that aircraft had on the clouds, it was found that their disruption of the clouds could lead to either snowfall or rain within a sixty mile radius around the airport. The unusual holes can therefore set off a reaction to create additional rain or snow.
Leader of the study and the author of related research paper, Andrew Heymsfield (National Center for Atmospheric Research – Bolder, Colorado), commented that this unintended weather phenomenon occurred approximately five percent of the time these hole-punches were created and this increases in winter from between ten to fifteen percent. To understand how this reaction happens, it is important to remember that airplanes take-off into the wind. Clouds generally have an average temperature of between zero to minus forty degrees Celsius. At these temperatures clouds are filled with cooled water droplets that are held in suspension. An aircraft then moving through these clouds is able to seed ice crystals, which in turn creates snowfall.
Seeding these droplets is a reaction created when the jet engines of the airplane force the clouds to expand, and with the air rushing either through the propellers or underneath the aircrafts wings, the air is cooled even further, which then cools the suspended droplets, making them heavier and therefore creating either rain or snow. With propeller aircraft the hole-punching formation occurs at about minus ten degrees, and at minus twenty degrees Celsius for jet planes. Aircraft that are fitted with propellers are six percent more likely to seed clouds, while jet aircraft only two to three percent.
Heymsfield went on to say that even though they now know and understand how cloud seeding works, and there is a possibility of altering rainfall and snowfall, airplanes trigger this effect purely accidentally and it does not occur each time.