the red sun, a danger in anticipation?

The appearance of a red sun in the sky is linked to many weather sayings and legends. ” Red sun in the morning, make the sailor tremble” ! The red color of the sun is always associated with a weather risk, a bad omen or a warning.

The phenomenon also appears in many works of art, literature, pictures or films.

This red hue, whether bright or dark, is linked to two events. The first is quite common, and the second a little less.

A red sun at sunrise or sunset is not abnormal

Sometimes the sun appears red during a simple sunrise or sunset. It is the distance that light travels in the atmosphere that causes such variations: colors with short wavelengths, such as blue, violet and green, cannot diffuse. At this time of day, when the sun’s rays have to travel a long distance, only long-wavelength colors are diffused: like red and orange.

It is the same mechanism that explains the spectacular “fire skies” at sunrise or sunset. On a purely meteorological level, the presence of a red sun on the other hand does not announce any threat, contrary to what the saying of the sailors suggests.

A red sun in the middle of the day, danger on the horizon!

The most impressive images of red sun are all related to the presence of particles in the sky, whether natural or not:

Smoke from fires: large fires around the world, such as those in California, Australia or Canada, generate a cloud of smoke that can stretch over several thousand kilometres. The particles are sent into the atmosphere by the winds which circulate, and the smoke can then cover the neighboring countries which are not affected by the forest fires.

This is why fires in Alberta in Canada can cause a red sun in the sky in the southern United States, just as fires in Portugal can create the same phenomenon over part of France. When the ashes are very numerous, only the longest solar rays can be filtered, and the red color is the only one that can appear. The sun therefore takes on a bright red hue even though the rest of the sky is completely dark due to the smoke.

Volcanic ash: the same phenomenon as that of fires occurs in the event of a volcanic eruption. In the case of volcanic ash, such as that from fires, the sun may appear red several days or even weeks after the fires or eruption have ended. Quite simply because the wind can continue to transport the particles over a long distance, even though the phenomenon that generated these ashes is over.

A cloud of pollution: certain types of pollutants and dust can reduce the visibility of the sun if these particles are too numerous. But others have the same effect as the ashes of fires and volcanoes. In highly industrial cities, such as those in Eastern European countries, it is not uncommon to see a red sun linked to a cloud of pollution.

Whether it is due to a fire, a volcano, or pollution, the presence of a red sun against a gray sky background in the middle of the day is in any case linked to a phenomenon that deserves to protect your respiratory tract as soon as possible: there is a danger to health, because these different types of particles are all harmful to health.