Wednesday, August 28, 2013

Summer Storms and Rainbows

Summer thunderstorms are always the highlight of this time of year. We have had a lot of moisture this last week. Even though the season is turning into fall the sun is still strong enough to kick-start some afternoon thunderstorms. Yesterday's storm was exciting. I was sitting inside when all of a sudden the winds picked up around 7:00 PM (19:00). This was a gust front associated with a thunderstorm that had just passed through Payson. (Maybe someday I'll write about gust fronts). The winds settled down a little bit and we had a brief downpour of rain--about a quarter of an inch. There was some lightning and thunder, too. While this was a fun to watch, it got rather chilly very quick. You can see in the charts below that the temperature following the gust front decreased quickly--about 20 degrees in 20 minutes.

Here is a link to my weather station during this time: Link. (For current conditions click "current conditions" on the right side panel.)

Today's storm was a little calmer. There was even a beautiful rainbow in the backyard. Looking a little closer, I saw two rainbows!
(c) BKB
(b) BKB
The brightest rainbow is the "primary bow." Rainbows are caused by light being refracted and reflected in raindrops. Sunlight looks white, but it actually consists of all the wavelengths of light. When that light travels through a water droplet, the different wavelengths of light are separated. When thousands of water droplets refract the light, we see a rainbow. The inside of the primary bow is always violet. As you move outward the colors go as followed: indigo, blue, green, yellow, orange, and red on the outside.

(c) BKB
The second bow is called, (you guessed it) the "secondary bow." The colors in the secondary bow are reversed, with red on the inside and violet on the outside. This is because this bow is caused by a double reflection inside the drop. You may have notice that the colors are more faint. This is because not all the light is reflected off the water droplet. For each reflection, some light passes through and never reaches your eye. The double reflection for the secondary bow thus looses more light than a single reflection.

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