A red sky during a storm can mean different things depending on the circumstances. Generally, a red sky is caused by dust particles or water droplets scattering certain wavelengths of light preferentially. The specific reasons why the sky appears red can provide clues about current or approaching weather conditions.
Rayleigh Scattering
One reason skies can turn red is due to Rayleigh scattering. This phenomenon occurs when sunlight passes through the atmosphere and shorter wavelengths like blue light are scattered away by gas molecules and airborne particles. This scattering effect causes the remaining longer wavelengths like red and orange to be transmitted through the atmosphere.
At sunrise or sunset when sunlight travels a longer path through the atmosphere, increased Rayleigh scattering removes much of the shorter blue light. This allows the sun to take on a reddish hue as more of the longer red wavelengths reach the viewer.
So in the mornings or evenings, a red sky is often simply a result of the angle of the sun and Rayleigh scattering. However, it can also signify dust particles or water vapor in the air which exaggerates this effect.
Water Droplets in the Air
Another reason skies can turn red during storms is due to the presence of water droplets in the air. During severe storms, the winds can carry moisture and condensation high up into the upper atmosphere.
The water droplets from this storm-driven updraft also contribute to scattering. Droplets that are about 1/10th the diameter of a human hair preferentially scatter red light the most strongly. This selective red scattering causes extra red wavelengths to come through while the shorter blue light is absorbed, making the sky appear red.
So a vividly red sky during a storm likely indicates that there is a large volume of water droplets being lifted high up into the upper atmosphere. This signifies the storm has a powerful updraft and a potential to strengthen even further.
Dust Particles
Dust lifted into the atmosphere can also contribute to red sky conditions. Dust particles coming from dry and arid regions are very effective at scattering the longer red and orange wavelengths.
As a storm system moves over an area, the winds and turbulence can stir up significant amounts of dust into the air. The red light scattered by these dust particles combined with the scattering from water droplets can lead to intensified red sky conditions.
A red sky caused by dust and moisture blown up by winds indicates the storm covers a large area and contains very strong winds extending into the upper atmosphere. The extensive amount of particles scattered through a deep atmospheric layer leads to the pronounced red color.
Predicting Storm Effects
| Red Sky Cause | Effects |
|---|---|
| Sun angle | Normal weather likely |
| Water droplets | Storm strengthening possible |
| Dust particles | Severe storm likely |
As this table summarizes, the cause of the red sky can signify different effects:
– A red sky simply due to sun angle usually does not indicate any severe weather change.
– A red sky caused by water droplets points to strengthening of an existing storm since it has powerful updrafts.
– A red sky also caused by dust stired up by a storm covers a large area and has strong winds reaching high altitudes, indicating a higher likelihood of severe impacts from the storm system.
So during a storm, a red sky caused solely by the angle of sunlight likely means the weather is following normal patterns. But a vivid red sky caused by moisture and dust suggests the storm is intensifying and expanding, so preparations should be made for severe conditions.
Famous Sayings
There are several famous sayings that reference red skies indicating storms:
– “Red sky at night, sailor’s delight. Red sky in the morning, sailors take warning.” – An old saying about how red skies can signify weather changes.
– “Evening red and morning gray, send the traveler on his way. Evening gray and morning red bring down rain upon his head.” – Another general rhyme about interpreting red sky meaning.
– “Sky with a lot of red in the morning, sailors take warning.” – Specifically notes red morning skies mean storms are likely coming.
The basis of these sayings is that a red sky at sunrise due to scattering means storm clouds are approaching from the west. Conversely, red sunset skies indicate fair weather will follow from the west.
Photographic Examples
Here are some photographs showing red sky conditions with storms:
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The left image shows a red sky at sunset with storm clouds beginning to enter from the west, suggesting rain is on the way. The right image shows a vivid deep red sky as a powerful thunderstorm approaches.
These examples visually demonstrate how red skies can indicate storms are either imminent or actively occurring due to the effects described earlier. The color also suggests the approaching or current storm is quite strong and expansive.
Conclusion
In summary, several factors can contribute to red skies during storms:
– Rayleigh scattering of sunlight at sunrise or sunset
– Water droplets lifted into the upper atmosphere
– Dust particles stirred up by winds
The red color results from certain wavelengths being scattered and transmitted preferentially. The specifics of the scattering can indicate how conditions are likely to evolve:
– Regular red skies just from sun angle don’t signify changes.
– Red skies from moisture signify a storm is intensifying.
– Red skies also caused by dust mean a severe storm is approaching or occurring.
So reading the clues provided by the color of the sky can help predict impacts from storm systems. Overall, dramatic red skies during storms require precaution as they often precede or signify intense weather conditions.
Bibliography
Reddy, Madhusudan. “Why are sunrises and sunsets sometimes so colorful?” ScienceABC. https://www.scienceabc.com/nature/universe/red-sunsets-and-red-sunrises-formation-rayleigh-scattering-mie-scattering.html
Taylor, Karla. “Vivid sunsets and sunrises: What causes them?” National Weather Service. https://www.weather.gov/fsd/why-are-sunrises-and-sunsets-red
Dunlap, Tonya. “Folklore, Sayings, and Science of Red Skies.” Farmers’ Almanac. https://www.farmersalmanac.com/red-skies-at-night-sailors-delight-sailors-warning-31820