Posts Tagged lightning
This year I was able to capture upward lightning flashes from a newly installed wind turbine complex northeast of Newell, South Dakota as well as lightning associated with the monsoon season in the Colorado Plateau. There were also some spectacular lightning displays in the my home area in the Northern High Plains. Below are some of the images captured.
Standard- and high-speed video highlights from the 2021 storm season are now available on my YouTube channel.
On the evening of Saturday, 23 May 2020 a strong linear storm passed over the South Dakota Badlands. As the sun began to set, the stunning orange and pink light illuminated the backside of the storm and its trailing stratiform precipitation area. As is common with mesoscale convective systems, this backside region produced numerous horizontally extensive lightning flashes many of which contained positive cloud-to-ground return strokes. Also common with these types of flashes, negative leaders raced through the layered positive charge regions above cloud base, while trailing positive leaders propagated below cloud base in trail of the negative leaders presumably through negative screening layer charge or negatively charge rain. This spectacular “spider” lightning is my personal favorite and this spectacle was one I will not soon forget. My daughter and I filmed the flashes with every camera we had available and the video below shows our best captures. Recordings were made from 30 to 1,500 images per second.
Captured a close negative ground flash while driving near Guernsey, Wyoming on 19 May 2020. You can hear the thunder on the dash cam in about a second after the flash. Recorded with the Phantom M321S at 1,500 images per second. In the frame prior to the return stroke, there appears to be a dim connection to the downward leader and ground. This is a camera artifact due to the saturating bright return stroke recorded in the following image (frame). The brightness “bleeds” over into the previous frame making it appear there is a connection or upward connecting leader present when in fact it is not.
Just as we have documented positive leaders developing from negative leader channels, we have also observed and analyzed negative leaders develop from positive leader channels. However, the physical process is noticeably different as it involves the development of recoil leaders in decayed positive leaders. Negative cloud-to-ground return strokes can occur during the horizontal propagation of positive leaders when the positive leaders decay and become cutoff from their original negative ends. A recoil leaders that develops along the positive leader channel paths can have its negative ends “veer off” the previously ionized channel and travel to ground via negative breakdown through virgin air causing a negative return stroke. The growing positive leader that follows the return stroke frequently decays with additional recoil leaders forming. The negative end of subsequent recoil leaders travel down the newly established channel path to ground, since it is more conductive due to its more recent ionization, causing additional negative return strokes resulting in repeated extension and growth of the horizontal positive leader end.
It is sometimes possible to recognize this type of flash solely from digital still imagery due to the geometry and shape captured during a single exposure. Below is a digital still image of the flash shown in the video above. The negative leader development that traveled to ground from the decayed positive leader channel displays recognizable negative leader patterns (erratic direction change and branching) and the brightness of the return stroke illuminates the channel back to the positive leader end which is in the left portion of the image. Notice the left curve where the negative leader return stroke channel joins the positive leader channel. If the downward negative leader was simply a branch of the initial horizontal propagating negative leader there would have been a right curve in the bright channel segment that traveled back in the direction from which the leader initially propagated (to the right).
We know from observation and analysis of horizontally extensive lightning flashes that often negative leaders travel horizontally through a layered positive charge region that spans large areas. We frequently observe that positive cloud-to-ground return strokes occur along the path the negative leaders travel but in trail of the negative leader tips. Current thinking is that the negative leaders become cutoff from their original positive ends and then develop new positive leader ends that propagate downward to the ground and cause a +CG return stroke that then further extend the negative leaders. Although we have frequently documented the positive leaders growing toward ground after negative leaders propagate in cloud, due to the clouds, we rarely are able to see the positive leader development initially take place from the previously formed negative leader channel. This video contains three cases where we see the negative leader channel from which a new positive leader develops, propagates to ground and causes a +CG return stroke that travels toward the end of the negative leaders, thus furthering their propagation. What is interesting and has yet to be understood is how the positive leader seems to develop from a still luminous negative leader channel segment. The luminosity in the negative leader channel suggests it is still actively carrying current and not completely cutoff. Therefore, we need to determine through further research the mechanism by which a positive leader is able to form and develop from this luminous channel. This behavior was first documented and described in a paper by Saba et al., 2009 using high-speed camera imagery.
Saba, M. M. F., L. Z. S. Campos, E. P. Krider, and O. Pinto Jr. (2009), High-speed video observations of positive ground flashes produced by intracloud lightning, Geophys. Res. Lett., 36, L12811, doi:10.1029/2009GL038791.
This is one of the best positive cloud-to-ground flashes that I have filmed. When you watch the video remember that lightning leaders grow as bidirectionally with a positive and negative end. We see the positive leaders of this flash below cloud base and the negative end of the leader network is higher up in the clouds and therefore not visible. There are two sets of positive leaders to focus on. The farther leaders are on the left descending to ground and the right positive leaders closer to the camera spread out horizontally along cloud base. Once the far positive leaders reach ground a return stroke occurs. Once the return stroke traverses the leader network, the connected channel grows as an upward propagating negative leader higher up in the storm. The closer leaders also have a negative end that is growing unseen in the upper part of the storm but these leaders do not connect with ground and continue to spread out horizontally. Frequently, some of the positive leader branches become cutoff and develop fast moving bidirectional recoil leaders that attempt to reionize the decayed positive leader branches. The negative end of the recoil leaders travel toward the negative end of the flash by racing toward the place where the positive leaders emerged below cloud base. This continues for quite some time. You may consider this to be a hybrid flash with a ground flash component (farther) and an intracloud flash component (nearer) both raising negative charge upward toward a positive charge region. This flash was filmed at 5,600 images per second.
This complex negative ground flash captured at 7,200 images per second shows negative leaders, negative return strokes with different termination points as well as multiple return strokes in the same channel. It also shows how negative leaders can redevelop from a decayed negative channel branch point and extend the negative leader branch further. The final return stroke is caused by a recoil leader that initiates in the cloud at the positive end of the flash (not visible) with the negative end of the recoil leader traveling along the previous return stroke channel and causing a final negative return stroke.
Early in the morning of 26 June 2018 in southwest Kansas, something wonderful happened. A lightning flash occurred that caused additional lightning to rise up from 14 wind turbines filling the sky with blinding channels of light. Hank Schyma (an accomplished storm chaser, photographer/videographer and all around interesting guy also known as Pecos Hank) was there to witness this amazing spectacle and captured it on video. A huge mesoscale convective system had developed earlier in the evening, and he had positioned himself on the trailing side in hopes of capturing massive horizontally extensive lightning flashes that tend to develop in the trailing stratiform region. He was not disappointed. He witnessed numerous spectacular flashes and a number of these involved upward leaders developing from a wind turbine complex nearby. He reached out to me and other scientists to share his observations, and we were floored by what he captured.
I have been studying upward lightning flashes since 2004 primarily in Rapid City, South Dakota where there are 10 towers positioned along a ridgeline that runs through the middle of town.
In 2013, we participated in a project to observe upward lightning from a wind turbine farm in north central Kansas. We managed to capture a few events with one involving 4 wind turbines.
Our research, analysis and findings show that most upward flashes in the summer convective season are triggered by preceding nearby positive ground flashes and/or cloud flashes in which horizontally extensive negative leader activity passes nearby tall objects. The rapid electric field change from the negative leader activity or positive cloud-to-ground return stroke combined with the shape of the tall object, which enhances the electric field locally, results in the initiation or triggering of upward positive leaders from the objects.
I had always wondered just how many wind turbines could initiate upward leaders when triggered by a nearby flash. Hank’s capture showed that up to 14 wind turbines could initiate upward leaders in a single flash. As far as I know, this is the most that has been observed to date. This flash was truly a Perfect Upward Flash and followed the textbook on how preceding flashes can trigger upward leaders.
Hank’s video shows incloud brightening that propagates toward the camera and over the wind turbines. This is negative leader activity that frequently travels through layers of horizontal positive charge that build up in the trailing stratiform region of mesoscale convective complexes. Lightning develops as a bidirectional leader which ionizes the neutral air due to the strong electric field caused by charge regions within a thunderstorm. The bidirectional leader has a negative end that has a surplus of electrons and the a positive end with a deficit of electrons.
Often when the negative leaders travel a large distance, they tend to become cutoff from the other end of the leader. Due to the still present strong electric field, the cutoff segment, which is still conductive, can polarize and develop a new positive end resulting in new positive leader propagation and corresponding renewed negative leader growth. Frequently, the new positive leader end will travel to ground and connect causing a positive cloud-to-ground return stroke, and that is exactly what happened as recorded by Hank’s camera. Positive leaders propagate to ground on the right side of the video and connect to ground causing a return stroke. This return stroke, which involves an incredibly fast propagating region of rapid electron acceleration, heating and intense light emission, travels up the channel at about 1/3rd the speed of light and through to the negative end of the leader network that was overlying the wind turbines. The resulting electric field change causes positive leaders to initiate and grow from the highest of the wind turbine blades. These upward positive leaders travel upward driven by the newly modified electric field created by the return stroke.
To have so many upward positive leaders develop shows that the area covered by the triggering leader network and magnitude of the electric field change from the return stroke was very large influencing all the wind turbines nearly at once. It truly was a Perfect Upward Flash and something to behold.
I would like to thank Hank for sharing this video with me so I could share its explanation with all of you. He recently created an excellent video on How Lightning Works which you can see on his YouTube channel. It is definitely worth seeing and explains our latest scientific understanding of lightning using his amazing video and imagery.
Unlike most lightning that initiates in the thunderstorm cloud as a bidirectional and bipolar leader that travels both upward and downward towards oppositely charged regions, upward lightning is unique in that it initiates from a tall object and the unidirectional leader only travels upward towards opposite polarity storm charge or a preceding triggering lightning flash component. Lightning-triggered upward lightning (LTUL) is caused by a nearby triggering lightning flash which has one of its components (either leader activity or a return stroke) pass close enough to the tall object to cause a large and rapid electric field change which in turn initiates a self-propagating upward leader from the object. Self-initiated upward lightning (SIUL) does not require a preceding nearby triggering lightning flash. Instead, the electric field due to storm charge generation within the cloud reaches a point at which a self-propagating leader initiates spontaneously. However, in this case the storm charge region is usually much lower and closer to the tall object and sometimes even envelopes the object. In both cases, the shape and height of the tower enhances the electric field locally near the tip so that ionization of the air and resulting leader formation takes place much easier than that over flat ground. In essence, if the tall objects (i.e., towers, wind turbines or buildings) where not there, the upward lightning would not occur.
We have researched upward lightning in Rapid City since 2004, and our findings show that the 10 tall towers along the ridge that runs through the city all have experience upward lightning. During the summer, we only observed lightning-triggered upward lightning and during intense winter storms with heavy snow and strong winds, we only observed self-initiated upward lightning. During the summer months from 2004 through 2014 we recorded recorded 122 upward flashes from the towers all of which were LTUL.
However, during the winter months, we only documented upward flashes during two major snow events. The first and most intense was the devastating blizzard of 4 Oct 2013. During a 21 hour period, the towers in Rapid City initiated 25 SIUL flashes. In addition, the South Dakota Public Broadcasting tower near Faith, South Dakota experienced 17 SIUL flashes. Although we focus our research during the summer months, we just happened to have an electric field meter and digital interferometer operating during the blizzard. The challenge with observing SIUL during heavy snow is that you cannot see the towers because they are obscured by the snow and low clouds. So you have to record the lightning by some other means. The electric field meter recorded the ambient electric field 5 km west of the towers, and the digital interferometer, 23 km east of the towers, mapped lightning leader activity in two dimensions (azimuth and elevation). The interferometer recorded five upward flashes before it lost power along with most of western South Dakota. Below is a video animation of the data recorded by the digital interferometer for one of the upward flashes. You can visualize that you are standing east of Rapid City looking west toward the towers. Each of the individual data points represents the azimuth and elevation to electromagnetic radiation generated by the lightning leader (and received by the sensor) as the leader propagated. The system records data in sequential 4 microsecond windows and determines the direction to the strongest signal in each time window. Since lightning tends to branch as it grows, you see the source points plot the spreading branched leaders as they grow. The leader clearly initiates from a single point and then spreads upward as it branches. Occasionally, you can see a rapid succession of source points that travel back along a branch toward the tower. These are recoil leaders which form on decayed branches in an attempt to reionize the branch.
And here is some video taken from my house during one of the upward flashes.
The only other time that we documented self-initiated upward lightning from the towers in Rapid City was during a strong snow event on Christmas Day 2016. There were three confirmed upward flashes.
So if it is snowing really hard in Rapid City and you hear thunder, chances are you can blame the towers.
If you would like to learn more about lightning, please visit my Education section
Below are journal and conference paper citations on the subject.
Asakawa, A., K. Miyake, S. Yokoyama, T. Shindo, T. Yokota, and T. Sakai (1997), Two types of lightning discharges to a high stack on the coast of the Sea of Japan in winter, IEEE Trans. Power Delivery, 12, 1222–1231.
Bech, J., N. Pineda, T. Rigo, and M. Aran (2013), Remote sensing analysis of a Mediterranean thundersnow and low-altitude heavy snowfall event, J. Atmos. Res., 123, 305-322, doi:10.1016/j.atmosres.2012.06.021.
Brook, M., M. Nakano, and P. Krehbiel (1982), The electrical structure of the Hokuriku winter thunderstorm, J. Geophys. Res., 87, 1207– 1215.
Heidler, F., M. Manhardt, and K. Stimper (2014), Self-Initiated and Other-Triggered Positive Upward Lightning Measured at the Peissenberg Tower, Germany, paper presented at the 2014 International Conference on Lightning Protection (ICLP), 13 – 17 Oct, Shanghai, China.
Lyons, W. A., T. E. Nelson, T. A. Warner, A. Ballweber, R. Lueck, T. J. Lang, S. A. Cummer, M. M. F. Saba, C. Schumann, K. L. Cummins, N. Beavis, S. A. Rudtledge, T. A. Samaras, P. Samaras and C. Young (2014), Large Scale Outbreaks of Thundersnow and Self-Initiated Upward Lightning (SIUL) During Two Blizzards, paper presented at the 23nd International Lightning Meteorology Conference, Mar 20 – 21, Tucson, Arizona.
Pineda, N., J. Figueras i Ventura, D. Romero, A. Mostajabi, M. Azadifar, A. Sunjerga, F. Rachidi, M. Rubinstein, J. Montanyà, O. van der Velde, P. Altube, N. Besic, J. Grazioli, U. Germann, and E. R. Williams (2019), Meteorological aspects of self-initiated upward lightning at the Säntis tower (Switzerland), J. Geophys. Res., doi: 10.1029/2019JD030834
Rakov, V. A., and M. A. Uman (2003), Winter lightning in Japan, in Lightning: Physics and Effects, chap. 8, pp. 308– 320, Cambridge Univ. Press, Cambridge, U. K.
Schultz, C. J., Lang, T. J., Bruning, E. C., Calhoun, K. M., Harkema, S., & Curtis, N. (2018). Characteristics of lightning within electrified snowfall events using lightning mapping arrays, J. Geophys. Res. Atmos., 123. doi: 10.1002/2017JD027821
Wang, D., N. Takagi, T. Watanabe, H. Sakurano, and M. Hashimoto (2008), Observed characteristics of upward leaders that are initiated from a windmill and its lightning protection tower, Geophys. Res. Lett., 35, L02803, doi:10.1029/2007GL032136.
Wang D. and N. Takagi, (2010), Characteristics of winter lightning that occurred on a windmill and its lightning protection tower in Japan, Proceedings of the 3rd International Symposium on Winter Lightning, Jun 13-15, Tokyo, Japan.
Wang D., and N. Takagi, Y. Takaki (2010), A comparison between self-triggered and other-triggered upward lightning discharges, Proceedings of the 30th International Conference on Lightning Protection, Sep 13-17, Cagliari, Italy.
Wang D., and N. Takagi (2012), Three Unusual Upward Positive Lightning Triggered by Other Nearby Lightning Discharge Activity, paper presented at the 22nd International Lightning Detection Conference, 2 – 3 April, Broomfield, Colorado, USA
Warner, T. A., T. J. Lang, and W. A. Lyons (2014), Synoptic scale outbreak of self-initiated upward lightning (SIUL) from tall structures during the central U.S. blizzard of 1–2 February 2011, J. Geophys. Res. Atmos., 119, doi:10.1002/2014JD021691.