All About Lightning and What It’s Like in Grand Canyon
by guest blogger Greg Zielinski
Monsoon season in Arizona
Mid-July and you are rafting on the Colorado River or hiking on one of the trails along the rims or that head into the Canyon. The clouds above have been getting taller and darker throughout the day and by mid- to late-afternoon, thunderstorms have become prevalent over the Canyon. July through September is monsoon season when thunderstorms are most likely to form in northern Arizona. They not only provide breathtaking photos and spectacular lightning displays, but they also can be deadly both from lightning strikes and heavy downpours and the resulting flash floods and debris flows. This article summarizes the lightning component of thunderstorms, how they form and some prevalent lightning myths. Incidentally, a common misconception about monsoons is that they are rain; they are NOT rain. Monsoons are seasonal winds or more accurately, they are regional airflow that varies with the seasons. When the monsoons kick-in for the Grand Canyon area, they bring moisture from the Gulfs of California and Mexico that lead to thunderstorm development.
Impressive lightning strikes can often occur during monsoonal thunderstorms around the Grand Canyon. As described below, the return stroke is the very bright streak in each photo. Left photo from National Park Service (NPS) as available at https://www.nps.gov/grca/planyourvisit/lightning-danger.htm. Right photo from Daniel Pawlak, NPS, as available at https://www.nps.gov/grca/learn/nature/weather.htm?mbid=synd_msntravel
Lightning formation and types of lightning
Thunderstorms are convective storms meaning that they form from rising warm, moist air. Together with these updrafts are downdrafts of cooler air that contain ice particles and graupel. Graupel are the white amorphous pellets that look like moth balls when they reach the ground. They form when snow crystals come into contact with supercooled water, that is, water below freezing, but still in liquid form. It is actually hard for a single liquid drop to crystallize into ice as it needs to have something to crystallize onto, thus it can remain in liquid from despite being below freezing. As the ice crystals and graupel particles come into contact with each other, electrons are stripped off of them with most positively charged particles moving to the cold, upper parts of the cloud and most negatively charged particles moving to the warm, lower parts of the cloud. This sets up the attraction of charges that causes lightning, the electrical discharge to neutralize these charges. Although the exact cause of lightning formation is not known, this is the best explanation put forth at the moment. The separation of charges in the cloud leads to one type of lightning, that is, lightning within the cloud. A second type of lightning is cloud-to-cloud or cloud-to-air lightning.
Given the accumulation of negative charges at the base of the cloud, positive charges are induced to accumulate at the surface to neutralize those negative charges in the cloud. The need to neutralize charges can lead to another type of lightning, that is, cloud-to-ground, the type that can be dangerous to people and create wildfires. However, there is another type of cloud-to-ground lightning that can be generated within a thunderstorm. Positive charges can accumulate in the uppermost part of the thunderstorm, the anvil part of the cloud. Negative charges would then be induced to accumulate at the surface setting-up the potential lightning strike. This scenario can lead to lightning 10 miles ahead of the core of the thunderstorm, although it has been observed up to 25 miles ahead of the core. This can be a dangerous situation when one is thinking they are safe with the thunderstorm still very far away.
Pictures of a supercell thunderstorm with its anvil top (top left) and three different types of lightning. Right top photo is within-cloud, bottom left photo is cloud-to-air, and bottom right photo is cloud-to-ground lightning. Pictures from NOAA Severe Storm Laboratory as available at https:// www.weather.gov/iln/skywarn_guide (top left) and https://www.nssl.noaa.gov/education/svrwx101/lightning/types/
The lightning strike
The cloud-to-ground lightning strike begins when the voltage at the base of the cloud reaches 9000 volts/meter. Such a high voltage is attained because air is a very poor conductor of electricity, thus a very high voltage is needed for the negative charges to move toward the Earth’s surface and connect with the positive charges accumulating below the cloud. The high voltage leads to a temperature of 5000˚F for a lightning bolt, about 5x the temperature of the surface of the sun.
Once enough voltage accumulates at the base of the cloud, an initial stream of negative charges heads toward the ground in the form of a pilot leader and subsequently as branching stepped leaders. As it gets closer, a spark is generated by the string of positive charges on the surface heading toward the cloud. This spark makes the connection with the negative charges thereby producing the return stroke back to the cloud, the brilliant flash seen with lightning. After the return stroke other dart leaders may progress toward the ground and if positive charges have accumulated at the surface, the process repeats.
One of the results of lightning is the formation of thunder, the sound made by the cooling and contraction of air after the lightning bolt moves through the air. The time between lightning formation and the resulting thunder can be used to estimate the distance from the observer to the lightning. The sound of thunder moves at about 5 sec/mile, thus the lightning is one mile away for every 5 sec since the flash was seen and the thunder heard.
Distribution of charges in the thunderstorm and on the Earth’s surface with the resulting sequence of events that leads to a cloud-to-ground lightning strike. Figures from the NOAA Jetstream program as available at https://www.noaa.gov/jetstream/lightning/how-lightning-is-created.
Misconceptions about lightning
There are several misconceptions about lightning that are fairly widespread among the general public. Here are a few of those myths and the reality of the scenario.
- MYTH: Lightning never strikes the same place twice. TRUTH: There are multiple examples of lightning striking the same place twice as all that is needed is the build-up of charges.
- MYTH: Lightning only strikes high spots. TRUTH: Higher spots are more likely to get struck, but anyplace can be struck as again, all that is needed is the accumulation of charges. TAKE-AWAY: Lightning can strike at the bottom of the Canyon and along the trails leading into the Canyon, not just on the rims.
- MYTH: The rubber tires protect you from lightning when in a car. TRUTH: The rubber has nothing to do with the protection when in a car. If lighting strikes the car, the electricity will move downward around the exterior metal of the car since the wheels ground the car. One TAKE-AWAY: Rubber-soled shoes will not protect you from lightning. If one really thinks about it, the extreme temperature of lighting can easily melt the shoes and pass into your body.
- MYTH: One type of lighting is heat lighting, that is, no thunder associated with the flash. TRUTH: Although the heating of the Earth’s surfaced and resulting rising air leads to lightning formation, the lightning is just too far away to hear the thunder.
Concluding thoughts
Lightning can produce some very spectacular displays resulting in interesting and fabulous photographs. However, it is deadly and should be respected. Consequently, be vigilant and aware of thunderstorms that may be forming around you especially if you are on the rims or on an exposed ridge. Be aware even when hiking to the bottom of the Canyon or at the bottom since lightning can reach all parts of the Canyon.
More detailed information regarding the science of lightning are available at the many websites of NOAA (e.g., National Weather Service, Severe Storm Laboratory, Jetstream Program) and the National Park Service.
Guest Blogger: Greg Zielinski is a retired professor in the fields of climatology, meteorology and geology. Internationally known for his work on the impact of volcanic eruptions on climate through ice core research, he has been a featured scientist in many documentaries including NOVA. He has published several books on weather and climate and was the Maine State Climatologist.
The Reality of Lightning at the Bottom of Grand Canyon (AzRA)
In the depths of the Grand Canyon, nature reigns supreme. When lightning strikes within the canyon, there’s little one can do but hope for the best as there are no structures or cars (with the exception of a few shelters along the Bright Angel trail) to take refuge in. Being lower down decreases the odds of a strike, as lightning tends to hit higher elevations. However, it’s crucial for visitors to understand that the reality is there’s no truly “safe” place from the lightning at the bottom of the canyon. If you’d like to hear more specifics on lightning in Grand Canyon, head over to The River Radius’ podcast about Lightning!
2 Comments. Leave new
I loved this post–it really helped me understand lightning better. Thank you!
So glad it was helpful to you, Laurie!