Vermilion drops falling from the sky, coloring roads and buildings with a crimson hue. If this painting spontaneously evokes the horrifying cinematographic imagination, it nevertheless describes a very real meteorological phenomenon, as fascinating as it is extremely rare. If the chronicles relating these purple precipitations were often considered as fabrications or dire omens, they are in reality provoked by a well-documented phenomenon.
When the sky cries blood: the red rains of Kerala
The Malabar Coast, in the Indian state of Kerala, is an exceptional place to study these famous rains of blood. For a century, this region has been the scene of several spectacular episodes of red rain : in July 1957, during the summer and fall of 2001, then three times in 2012.
Weather Fact: It rained “blood” in India
The Kerala red rain occurred from July to September 2001. Heavy downpours of red rain fell sporadically on the southern Indian state of Kerala.
Yellow, green and black rain was also reported. The rains were colored by algae spores. pic.twitter.com/r2O9t66UGa— Kashmir Weather (@Kashmir_Weather) July 26, 2020
These manifestations, of a color close to hemoglobin, initially fueled certain strange hypotheses, notably that of the explosion of a meteorite which would have dispersed its fragments in the atmosphere. However, other investigations concluded that no meteorite was the cause of these rains.
The secrets of mysterious coloring
The key to this enigma resides in a microscopic organism : THE Trentepohliaa filamentous green algae whose cells are full of carotenoids, the same pigments that give carrots their beautiful color. This composition can vary its color from green to bright orange.
This algae, which usually covers the bark of trees, is thrown into the air during specific weather episodes. Indeed, red precipitation systematically occurs after the passage of a gust fronta phenomenon characterized by a sudden acceleration in sales preceding storm formations. When warm, humid air rises into the atmosphere, it creates powerful updrafts and these can give rise to thunderstorms. During a thunderstorm, cold, dense air quickly descends to the ground, creating this famous gust front.
The presence of these organisms in the atmosphere is therefore not accidental, because it results a specific combination of environmental factors. The violent winds, characteristic of storm fronts, tear these microorganisms from their natural habitat and propel them into the upper layers of the atmosphere.
There they can be transported over considerable distances before being thrown to the ground by the rains. This mechanism also explains why these phenomena can occur in regions far from areas where the plant naturally proliferates. Trentepohlia. A rational explanation, which does not mean losing the intriguing nature of these red rainswithout any danger to humans.
- Red rains, observed particularly in Kerala, are caused by micro-organisms projected into the atmosphere.
- These algae, rich in carotenoids, give this famous red tint to precipitation.
- Strong winds and storms carry these algae, which then fall with the rain.
