We had an amazing sunrise Friday in the Tennessee Valley. There were purple, pink and red colors in the sky ahead of the approaching storms. You’ve probably heard the phrase, “Red sky at night, sailor’s delight, red sky in the morning, sailor take warning.” This implies a red sky in the morning would mean bad weather is on the way.
In order to understand why, let’s talk about why we see such colorful sunrises and sunsets.
The sky is blue because of “selective scattering” of blue and violet light by air molecules. Scattering is the reflection of light by particles. We also call this “Rayleigh scattering.”
Clean air molecules scatter violet and blue light well which is why the sky is blue. Those blue and violet colors are shorter wavelengths.
However, aerosols are larger particles and they scatter red and orange light better. Sunlight takes a longer path through the Earth’s atmosphere at sunset. The violet and blue colors are scattered out of the sunlight path, which is why we see the sky as red or orange. Red is a long wavelength. During sunrises and sunsets, the sun’s rays travel through a longer path of the atmosphere which helps with scattering.
Now back to the phrase, “Red sky at night, sailor’s delight, red sky in the morning, sailor take warning.” In the case of Friday morning, the sky was fiery red. This means that high pressure is moving out and low pressure is moving in. The reason we know this is because under high pressure, the air is sinking and there can be an inversion or warmer layer above the surface. The inversion would trap dust particles near the surface. Aerosols scatter reds and oranges better. Looking east at the red colors at sunrise, we know high pressure is there and moving out which means low pressure is moving in because our weather moves from west to east. Low pressure is associated with rain and thunderstorms. High pressure is associated with tranquil weather.
Check out some other beautiful sunrise pictures from News 19 viewers in the Tennessee Valley.