Flying bugs blamed for bad weather
Published 24/05/2011 | 16:08
High-flying bugs in the atmosphere may largely be to blame for bad weather, scientists have claimed.
Numerous bacteria have been found concentrated in the centre of hailstones. The discovery suggests that airborne microbes play a leading role not just in hail storms, but other weather events.
All precipitation - rain, hail, snow or sleet - begins with ice crystals forming around cloud particles.
Dust grains and pollution droplets may both serve as "nucleating particles". But the new find has helped confirm suspicions that in many cases living micro-organisms cause the rain to fall.
Lead researcher Dr Alexander Michaud, from Montana State University in Bozeman, US, said: "Bacteria have been found within the embryo, the first part of a hailstone to develop. The embryo is a snapshot of what was involved with the event that initiated growth of the hailstone.
"In order for precipitation to occur, a nucleating particle must be present to allow for aggregation of water molecules.
"There is growing evidence that these nuclei can be bacteria or other biological particles."
Dr Michaud's team analysed hailstones over 5cm in diameter that were collected after a storm in June last year.
The large stones were separated into four layers, each of which was analysed in turn. Living bacteria that could be grown in the laboratory were present in the highest numbers in the inner cores of the hailstones.
The research has been presented at the annual meeting of the American Society for Microbiology in New Orleans.