If the sky turns a green colour when a thurnderstorm is approaching, does it mean that we are in for violent weather like tornadoes or giant hail stones? Lots of people associate a green stormy sky with imminent extreme weather conditions. However is this a physically proven reality or just an urban legend?
Sometimes when a storm is approaching the sky turns a green colour. According to popular belief, when the sky takes on a green tinge it is a clue that violent weather is about to erupt. Normally this includes tornadoes or giant hailstones. In regions where tornadoes are a common phenomenon – like in the centre of the United States – the sight of a green sky urges people to get themselves to safety either their basement or an adapted shelter. These associations have been spread as a sort of urban legend, so it is difficult to unravel the false from reality. What do researchers have to say about this phenomenon?
Green thunderstorms is the name given to the unusual storms which begin with a green hue in the clouds. One hypothesis suggests that the ground indirectly gives the clouds this greenish tint by reflecting the surrounding light when the land is covered in green vegetation (G.D Frier, 1992). However, measurements made by spectrophotometer prove this is not a necessary or sufficient condition for the phenomenon to occur. Between 1995 and 1996, American researchers chased these thunderstorms and recorded 15 having a hue considered green by a human observer. They were able to measure the storms’ light spectrum characteristics. Their results showed that the phenomenon is not significantly related to the nature of underlying soil *, but does however originate in the sky.
* For example, green thunderstorms can be found over Oklahoma red-brown lands.
Related articles :