Editor’s note: David Deen is river steward for the Connecticut River Watershed Council. CRWC is celebrating 60 years as a protector of the Connecticut River.
Refraction, ionization, evaporation, condensation, convection, static electricity and the rotation of the earth are some of the natural processes that create many wondrous events visible in our sky. It is hard to think about all those things when it is raining cats and dogs and there is lightning crashing around you.There is an old pilot’s cliché, “It’s not the clouds that get you; it’s the rocks in the clouds.”
Well, for people who flyfish, “It’s not the rain in a storm that gets you, it’s the lightning.” When lightning streaks the sky, it is time to head for the car. Once you are in relative safety and have to stow your fly rod, there’s time for some idle speculation.
For example, how strange a summer thunderstorm might seem to an extraterrestrial plunked onto the surface of the earth. A storm complete with towering altocumulus clouds, lightning, thunder, hail, downpouring rain and high winds? What would our visitor think of a rainbow following the storm or the steamy tendrils of ‘mountain spirits’ rising from our ridgelines?
Our understanding of the natural forces that cause thunderstorms does not lessen our amazement when we experience one. Most know that when the sun heats the earth, it heats the air that rises. If the air holds sufficient moisture in the form of water vapor and if the air aloft is cool enough, the vapor condenses into clouds. The clouds associated with thunderstorms might reach an altitude of 12 miles, known as Armstrong’s line, where the force of the upper winds blows the clouds flat to form the classic anvil-like flattop.
Clouds produce rain when two things occur simultaneously, the humidity in the cloud reaches supersaturated moisture levels and there are particles around which water drops can form. Supersaturation happens when humidity levels exceeded the air’s ability to hold that humidity as vapor. But in the absence of ions or dust particles even supersaturated air, which has up to 700 percent humidity, will not form water drops. Only when there is supersaturated air and particles or ions to form raindrops, will it rain.
When you see lightning, you are not seeing the electricity but the air molecules glowing from the tremendous heat of temperatures of over 50,000 degrees Fahrenheit as the stroke passes through the air.
Flyfishermen wearing waders and a raincoat usually have enough protection to keep them fishing in the rain at least until the clouds flash lightning. But lightning releases a primal fear in anyone who sees it even from a safe distance, and well it should. Now, think about how strange this phenomenon would seem to someone who has never before seen lightning.
A bolt of lightning can be from one inch to one foot in diameter depending on the phase (earlier to later) of the stroke. The length of a lightning stroke can be up to two miles long and it happens in milliseconds, with a big stroke releasing several billion volts of energy. When you see lightning, you are not seeing the electricity but the air molecules glowing from the tremendous heat of temperatures of over 50,000 degrees Fahrenheit as the stroke passes through the air.
Thunder is a shock wave, the after-effect of heating the air molecules to such a high temperature so quickly. As loud as thunder from a close stroke can be, the sound represents only about one percent of the energy of the shock wave. You can only hear thunder at a maximum distance of about seven miles, because the air molecules between the listener and the shock wave absorb the sound.
Distilled water is not a great conductor of electricity, but the amazing ability of water to take up other substances can turn water into a conductor. When substances dissolve, the molecules break apart into negatively and positively charged ions and they are only too happy to conduct electricity. Add to that the properties of the fly rod, which is most often graphite these days. As it happens, graphite is a great conductor of electricity. The ions in the water, which are good conductors, and the graphite rod add up to a grounded target waving a lightning rod above his or her head. A bad choice that could lead to fried fisherman.
The clouds begin to clear. As we step out of the car, the final act of this extraordinary weather show is a lovely multi-colored streak that hangs in the sky — two rainbows, one above the other, with a darker strip between them. The upper one is fainter and its colored stripes an exact reversal of the order in the primary rainbow.
Down through the ages, rainbows have enticed such luminaries of science as Sir Isaac Newton and Roger Bacon to study them. They defined the angle from the path of the sunlight to where the rainbow forms, 138 degrees for the primary rainbow and, if one is formed, 130 degrees for the secondary rainbow. The darker space between the two rainbows is the “Alexander dark band” named after another rainbow researcher, Alexander of Aphrodisias, a third century Greek philosopher of the Peripatetic school.
As much fun as it was to take shelter and speculate on how strange the storm might seem to an extraterrestrial visitor, once the storm passed it was time to go back to fishing. Enough of idle speculation.
